Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Keiko Sasaki Last modified date:2021.05.13

Professor / Resources System Engineering / Department of Earth Resources Engineering / Faculty of Engineering


Papers
1. Sekar Karthikeyan, Chitiphon Chuaicham, Balakumar Vellaisamy, Wei Li, Bunsho Ohtani, Keiko Sasaki, Cubic Cu2O nanoparticles decorated on TiO2 nanofiber heterostructure as an excellent synergistic photocatalyst for improving H2 production and sulfamethoxazole degradation, Appl. Catal., B, https://doi.org/10.1016/j.apcatb.2021.120221, 294, 120221, 2021.05, We report a simple strategy for providing a homogenous TiO2 nanofibre host environment to stabilize Cu2O nanoparticles with an average size of ~60 nm and high dispersibility. We found that the small fraction of Cu2O nanoparticles in direct contact/partially submerged with TiO2 nanofibre arrays (diameter ~300 nm and length ~651 nm) showed excellent synergistic Cu2O/TiO2-NF photocatalyst behaviour for an H2-1.h-1 with an apparent quantum efficiency of 3.6 %. The significant H2 production rate was much higher (factor of ~6.5 times) compared with unmodified TiO2-NF. In addition, the synergistic Cu2O/TiO2-NF photocatalyst showed significant sulfamethoxazole oxidative-degradation (7× 10-2 mmol.g-1.min-1) within 10 min and was highly stable during five cycles. The synergistic interfacial contact further verified by band alignment and the charge carrier mechanism was confirmed by the energy-resolved distribution of electron traps, electrochemical transient photocurrent, and electrochemical impedance (EIS)..
2. Subbaiah Muthu Prabhu, Chitiphon Chuaicham, Chang Min Park, G. Paruthimal Kalaignan, Keiko Sasaki, Synthesis and characterization of defective UiO-66 for efficient co-immobilization of arsenate and fluoride from single/binary solution, Environ Pollution, in press., 2020.10.
3. Mengmeng Wang, Hirofumi Akamatsu, Ismaila Dabo, Keiko Sasaki, Environmental impact of amino acids on the release of selenate immobilized in hydrotalcite: Integrated interpretation of experimental and density-functional theory study, Chemosphere, in press, 2021.03.
4. Keiko Sasaki, Shingo Nakama, Quanzhi Tian, Binglin Guo, Mengmeng Wang, Ryoichi Takagi, Tomohiko Takahashi, Elution characteristics of undesirable anionic species from fly ash blended cement in different aqueous solutions, J. Environ. Chem. Eng., in press, 2020.12.
5. S. Karthikeyan, A. Kassam, Y. Bai, B. Coulson, R. E. Douthwaite, A.F. Lee, K. Sasaki, W. Li, Hierarchical bismuth vanadate/reduced graphene oxide composite photocatalyst for hydrogen evolution and bisphenol A degradation, Applied Materials Today, in press, 2021.01.
6. Sekar Karthikeyan; Chitiphon Chuaicham; Umamahesh Balijapalli; Wei Li; Adam Fraser Lee; Keiko Sasaki, Surfactant- and template-free hydrothermal assembly of Cu2O visible light photocatalysts for trimethoprim degradation, Applied Catalysis B: Environmental, in press., 2020.11.
7. Sekar Karthikeyan; Ahmed Kassam; Yang Bai; Keiko Sasaki; Wei Li, Quantum dot bismuth vanadate/reduced graphene oxide photocatalyst for hydrogen evolution and bisphenol A degradation, Applied Materials Today, in press, 2020.11.
8. Chitiphon Chuaicham, Yihuang Xiong, Sekar Karthikeyan, Weinan Chen, Li Zhang, Ismaila Dabo, Keiko Sasaki, Z-scheme heterojunction between Zn-Ti layered double hydroxide and Fe-bearing montmorillonite for the photocatalytic reduction of chromate, Appl Surf Sci, in press, 2020.07.
9. Ahmad T. Yuliansyah, Satoshi Kumagai, Tsuyoshi Hirajima, Keiko Sasaki, Production of valuable chemicals from oil palm biomass using hot-compressed water method, Journal of Material Cycles and Waste Management, 10.1007/s10163-020-01073-8, 2021.02, Oil palm industry discharges a large amount of biomass waste which can be converted into energy and chemicals. Hence, several biomass conversion methods are available, such as fermentation, pyrolysis, and gasification. In this work, the hot-compressed water method was proposed to produce valuable chemicals from oil palm biomass (oil palm fiber, shell, and empty fruit bunches). Each material was individually treated in a batch autoclave reactor at 200–300 °C for 30 min. After separation, the total organic carbon of the liquid product was measured by a Shimadzu TOC-5000A instrument, while its composition was analyzed by HPLC and GC/MC apparatus. Experimental results showed that liquid product of oil palm wastes contains various chemicals such as glucose, xylose, 5-HMF, furfural, acetic acid, formic acid, phenol, catechol, and phenol 2,6-di-methoxy. This liquid product composition was strongly dependent on the temperature treatment. In general, sugar-derived compounds (glucose, xylose, 5-HMF, furfural, acetic acid, formic acid) were primarily found in lower temperature; meanwhile, lignin-derived compounds (phenol, catechol, and phenol 2,6-di-methoxy) were mainly obtained in higher temperature..
10. Kojo T. Konadu, Ryotaro Sakai, Diego M. Mendoza, Chitiphon Chuaicham, Hajime Miki, Keiko Sasaki, Effect of carbonaceous matter on bioleaching of Cu from chalcopyrite ore, Hydrometallurgy, 10.1016/j.hydromet.2020.105363, 195, 2020.08, Natural carbonaceous matter aided the bioleaching of Cu from chalcopyrite concentrates. The oxidative dissolution of chalcopyrite was enhanced more significantly by anthracite than carbonaceous matter in double refractory gold ore (DRGO). This was achieved through Galvanic interactions between the chalcopyrite and natural carbonaceous matter. Measurement of impedance verified that the electro-resistance is smaller in anthracite, which has a greater graphitic degree than carbonaceous matter in DRGO. The electron shuttle between chalcopyrite and the Fe3+ /Fe2+ redox couple was facilitated not only by the amounts of carbonaceous matter but also the degree of graphitization of carbonaceous matter. A higher graphitization degree increased the electron conductivity of the carbonaceous matter to help mediate Cu bioleaching while avoiding direct contact of thermophile cells with refractory copper sulfides..
11. Binglin Guo, Yuta Kamura, Paulmanickam Koilraj, Keiko Sasaki, Co-sorption of Sr2+ and SeO42− as the surrogate of radionuclide by alginate-encapsulated graphene oxide-layered double hydroxide beads, Environmental Research, 10.1016/j.envres.2020.109712, 187, 2020.08, Graphene oxides (GO) and layered double hydroxides (LDHs) were applied to produce alginate beads for the remove of 90Sr2+ and 79SeO42−. The Freundlich isotherm indicated that the Sr2+ sorptions were based on the energetically heterogeneous multilayer surfaces. In contrast, the sorption behavior of SeO42− fitted to the Langmuir adsorption isotherm models, indicating that the removal of SeO42− was caused by the ion-exchange of LDHs. The synthesized LDH/GO alginates beads were also applied for setting up small-bore adsorption columns with loading synthetic SeO42− and Sr2+ contaminated wastewater. Based on the water chemistry, the adsorbed amount of Sr2+ significantly increased after using alginates beads, which was attributed to the functional groups of either GO or alginic acid. The incorporated SeO42− was highly depended on the contents of fabricated LDHs in alginate beads. Specifically, the adsorption capacity of Sr2+ (0.85–0.91 mmol/g) on GO slightly increased after alginates fabrication. Therefore, it was deduced that this layered material was partially exfoliated during the manufacture and thus increased the sorption sites. Applications of LDH/GO alginates beads in the removal of both Sr2+ and SeO42− in water and soil treatment have a significant impact on the environmental remediation..
12. Keishi Oyama, Kazuhiko Shimada, Junichiro Ishibashi, Keiko Sasaki, Hajime Miki, Naoko Okibe, Catalytic mechanism of activated carbon-assisted bioleaching of enargite concentrate, Hydrometallurgy, 10.1016/j.hydromet.2020.105417, 196, 2020.09, The catalytic mechanism of activated carbon-assisted bioleaching of enargite concentrate (enargite 37.4%; pyrite 47.3%) was investigated by employing microbiological, electrochemical and kinetic studies. By using moderately thermophilic microorganisms at 45 °C, the final Cu dissolution was improved from 36% to 53% at 0.2% (w/v) activated carbon. An excess activated carbon addition showed an adverse effect. The enargite mineral itself favored higher solution redox potential (Eh) for solubilization. However, the dissolution of co-existing pyrite, which also favors high Eh, immediately hindered enargite dissolution through the passivation effect. The surface of activated carbon functioned as an electron mediator to couple RISCs oxidation and Fe3+ reduction, so that elevation of the Eh level was controlled by offsetting microbial Fe3+ regeneration. As long as the Eh level was suppressed at <700 mV, the dissolution of pyrite was largely avoided, enabling a steady and continuous dissolution of the enargite mineral through the surface chemical reaction model. When the Eh-control by activated carbon becomes no longer sustainable and the Eh hits 700 mV, rapid pyrite dissolution was initiated and the surface chemical reaction of enargite dissolution came to an end. Arsenic species dissolved from enargite was constantly immobilized with an efficiency of 75–90% as amorphous ferric arsenate. However, the sudden initiation of pyrite dissolution also triggered the re-solubilization of ferric arsenate. Therefore, the sustainable Eh-controlling effect was shown to be critical to enable longer Cu dissolution from enargite as well as stabilization of As precipitates..
13. Kojo T. Konadu, Diego M. Mendoza, Robert J. Huddy, Susan T.L. Harrison, Takashi Kaneta, Keiko Sasaki, Biological pretreatment of carbonaceous matter in double refractory gold ores
A review and some future considerations, Hydrometallurgy, 10.1016/j.hydromet.2020.105434, 196, 2020.09, The pretreatment of carbonaceous material in double refractory gold ores (DRGO) is necessary to decrease preg-robbing of gold and maximize gold recovery. DRGO contains of carbonaceous matter and gold grains encapsulated in sulfide minerals, which typically results in very poor gold recovery. However, there is growing interest in DRGO because some estimates show that it makes up about a third of the total available gold for production by mining. This can be achieved by chemical and biological techniques, however, the chemical techniques like flotation, surface passivation and chemical oxidation have received more extensive study and either have to be retooled or modified to be applied to the carbonaceous matter in the DRGO. In comparison, the biological techniques are relatively unknown with significant gaps in the knowledge about the bio-treatment mechanism, byproducts and avenues for scaling up like bioreactor design. This study reviews the enzymatic pretreatment of DRGO to facilitate gold recovery and minimize reagent consumption. It focuses on the potential for application of oxidative enzymes like lignin peroxidase, manganese peroxidase and laccase to pretreat carbonaceous matter in DRGO with or without an additional step of sulfide oxidation and addresses characterization of byproducts of the enzymatic decomposition. Further, potential bioreactor configurations for the enzymatic decomposition without direct contact of ore with microorganisms are considered, both in terms of understanding the mechanisms within the pretreatment and in terms of application..
14. Chitiphon Chuaicham, Radheshyam Rama Pawar, Sekar Karthikeyan, Bunsho Ohtani, Keiko Sasaki, Fabrication and characterization of ternary sepiolite/g-C3N4/Pd composites for improvement of photocatalytic degradation of ciprofloxacin under visible light irradiation, Journal of Colloid And Interface Science, 10.1016/j.jcis.2020.05.064, 577, 397-405, 2020.10, The development of high-quality photocatalytic materials for the degradation of organic pollutants under visible light irradiation is a vital field of research. In the present study, a composite of natural sepiolite clay and synthetic graphitic carbon nitride (CN) mixed with dispersed palladium nanoparticles was developed for the efficient photocatalytic degradation of ciprofloxacin (CIP) under visible light irradiation. The sepiolite, CN, and composite materials were characterized by several techniques. The sepiolite/CN composite (SC30%) displayed superior activity than pristine sepiolite and CN, resulted from the generation of new electron trap states in the interfacial contract between sepiolite and CN to suppress the charge recombination of CN. Furthermore, the well-dispersed of 1 wt% Pd-nanoparticles in the SC30% composite collectively enhanced CIP degradation by avoiding the recombination of photogenerated electrons and holes. Additionally, the electron trap states on the surface of all samples were studied using novel reversed double-beam photoacoustic spectroscopy to understand electron transfer in the composites related to the photocatalytic degradation mechanism of CIP. The developed sepiolite/CN/Pd(0) composite can act as a potential catalyst for the degradation of organic pollutants in wastewater under visible light irradiation..
15. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Bubble interactions with chalcopyrite and molybdenite surfaces in seawater, Minerals Engineering, 10.1016/j.mineng.2020.106536, 157, 2020.10, The detrimental effect of seawater on Cu-Mo flotation has attracted much attention in recent years, which has mainly been focused on altering the detrimental effect of seawater on the floatability of molybdenum ore. The interaction between bubbles and particles during flotation is a key factor in understanding the detrimental effect of seawater. Therefore, this study aimed to investigate the effect of seawater on bubble-particle interactions with chalcopyrite and molybdenite surfaces. Moreover, the effect of emulsified kerosene, a typical molybdenite collector, on bubble-particle interactions in seawater was investigated. Artificial seawater was used as a seawater model solution in this study. Flotation tests using pure chalcopyrite and molybdenite showed that the addition of emulsified kerosene to artificial seawater at a specific pH could selectively improve the floatability of molybdenite while maintaining the low floatability of chalcopyrite. A study of the bubble-particle interactions was then performed to analyze the phenomenon. It was found that the kerosene adsorbed at the air/liquid interface of the bubble improved the bubble aspect ratio and reduced the bubble rise velocity in artificial seawater. Moreover, kerosene could accelerate the formation of three-phase contact between the bubble and both mineral surfaces at the natural pH of artificial seawater. Additionally, this study showed that seawater colloidal precipitate formed under high pH conditions might be adsorbed on the mineral surfaces and might improve the stability of the intervening liquid film on the surface, thus preventing bubble-particle attachment and decreasing mineral recovery. Under these high pH conditions, the emulsified kerosene and seawater precipitate might compete in terms of adsorption on the mineral surfaces and the flotation results would most likely depend on the kerosene and hydrophilic adsorbate coverage on the mineral surfaces..
16. Li Zhang, Srinivasarao Kancharla, Keiko Sasaki, Synthesis and characterization of imidazole-bearing polymer-modified montmorillonite for adsorption of perchlorate, Applied Clay Science, 10.1016/j.clay.2020.105859, 199, 2020.12, Poly (4-vinylbenzyl methylimidazolium chloride) (PIm) in different stoichiometric amounts were applied for the modification of montmorillonite (Mt). The distribution of the distinguished Im+ (vinylbenzyl methylimidazolium cation) species attached to Mt. layer and the vinylbenzyl methylimidazolium chloride (Im-Cl) species with the counter ion was investigated through a meticulous calculation based on TG-DTA, CHN analysis, and the measurements of released Cl during modification. The constructions of the PIm as the modifier on Mt. were illustrated at a molecular level. Two configurations of intercalated PIm were proposed based on the XRD results, and the morphologies of PIm arrangement on the composites were characterized by FTIR, SEM, and N2 adsorption/desorption measurements. The construction and arrangement of PIm had a significant effect on the migration of ClO4 in the channels or on the surface of the PIm-Mt composites as suggested by the kinetics modeling. The previously calculated Im-Cl amount on PIm-Mt was comparatively discussed with the calculated theoretical adsorption capacity obtained by isotherms modeling and the experimental adsorption amount in practice. The combined analysis of the chemical interaction and theoretical statistics helped to elicit the dominant ion-exchange mechanism assisted by the dynamic re-distribution of anionic and cationic species in the aqueous phase during adsorption. Using the strategy to increase the hydrophobicity of the quaternary ammonium site, a remarkable selectivity of ClO4on PIm-Mt was achieved over NO3, Cl and SO42− with 50 times higher concentrations and low dosage of the adsorbents. Moreover, the significant reduction of the organo-modifier release was observed on the multiply charged macromolecule which was attributed to the constraint among the repeated units throws chemical bonds. Both the improved selectivity and the reduced organic release enable the PIm-Mt to become a more suitable adsorbent for water treatment of ClO4..
17. Quanzhi Tian, Mengmeng Wang; Binglin Guo; Haijun Zhang; Keiko Sasaki, Effect of Si/Al molar ratio on the immobilization of selenium and arsenic oxyanions in geopolymer, Environmental Pollution, in press., 2020.10.
18. Diego M. Mendoza, Kojo T. Konadu, Yuji Aoki, Misato Kameya, Keiko Sasaki, Carbonaceous matter degradation by fungal enzyme treatment to improve Ag recovery from an Au-Ag-bearing concentrate, Miner Eng, in press., 2020.09.
19. Binglin Guo,Yongshan Tan, Lei Wang, Liang Chen, Zuliang Wu, Keiko Sasaki, Viktor Mechtcherine, Daniel C.W. Tsang, High-Efficiency and Low-Carbon Remediation of Zinc Contaminated Sludge by Magnesium Oxysulfate Cement, J. Hazard. Mater., https://doi.org/10.1016/j.jhazmat.2020.124486, in press., 2020.08.
20. Binglin Guo, Quanzhi Tian, Tsubasa Oji, Lei Wang, Daniel C.W. Tsang, Keiko Sasaki,, Hydroxylated calcined dolomite as an effective and sustainable substitute of lime to precipitate as ettringite for treatment of selenite/selenate contaminated wastewater, Colloids Surf., A, in press., 2020.07.
21. Li Zhang, Srinivasarao Kanchela, Keiko Sasaki, Synthesis and characterization of imidazole-bearing polymer modified montmorillonite for adsorption of perchlorate, Appl. Clay Sci., in press, 2020.07.
22. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima; Hajime Miki; Keiko Sasaki, Bubble interactions with chalcopyrite and molybdenite surfaces in seawater, Minerals Engineering, https://doi.org/10.1016/j.mineng.2020.106536, 157, 106536, 2020.07.
23. Keishi Oyama, Kazuhiko Shimada, Jun-ichiro Ishibashi, Keiko Sasaki, Hajime Miki, Naoko Okibe,, Catalytic mechanism of activated carbon-assisted bioleaching of enargite concentrate, Hydrometallurgy , doi.org/10.1016/j.hyc!romet.2020.105417, 196, 105417, 2020.07.
24. Keiko Sasaki, Yoshikazu Hayashi, Takeshi Nakamura, Binglin Guo, Quanzhi Tian, Stabilization of borate by hot isostatic pressing after co-precipitation with hydroxyapatite using MAP, Chemosphere, 10.1016/j.chemosphere.2020.126860, 254, 2020.09, Boric acid is one of the most mobile inorganic contaminant species in nature due to its pKa of 9.23. Co-precipitation of borate with hydroxyapatite (HAp: Ca5(PO4)3OH) facilitates the simultaneous removal of borate with co-existing oxoanions in natural waters. The cost of phosphate is an impediment to industrialize the co-precipitation of borate with HAp for treatment of geothermal waters. In the present work, an inexpensive industrial by-product of magnesium ammonium phosphate (MAP) derived from sewage sludge, was examined as a phosphate source. MAP includes 89% pure magnesium ammonium phosphate, resulting in better performance than the pure chemical form of NH4H2PO4, because Mg2+ and Al3+ (trace elements in MAP product) play roles in enhancing the removal rate of borate and lowering the equilibrium borate concentration. These ions have a good affinity with phosphate to nucleate crystal seeds independently of powdery Ca sources. To reduce the bulky volume of solid residues, hot isostatic pressing (HIP) was applied. There is structural water in HAp; therefore, the greatest volume reduction was achieved with 78.3 ± 2.0% (n = 3). Additionally, a synergic effect to suppress the released borate, greater than the sequential combination of calcination and cold isostatic pressing was accomplished in the toxicity contents leaching procedure (TCLP) test. This is not due to larger crystal sizes alone, but it is derived from boron stabilization in HAp at an atomic level by the synergic effect of heating and pressing simultaneously..
25. Ahmad T. Yuliansyah, · Satoshi Kumagai, · Tsuyoshi Hirajima, · Keiko Sasaki, Production of valuable chemicals from oil palm biomass using hot‑compressed water method, J. Mater. Cycles Waste Manage., https://doi.org/10.1007/s10163-020-01073-8, in press, 2020.07.
26. Quanzhi Tian, Binglin Guo, Keiko Sasaki, Influence of silicate on the structural memory effect of layered double hydroxides for the immobilization of selenium, Journal of Hazardous Materials, 10.1016/j.jhazmat.2020.122674, 395, 2020.08, The influence of silicate on the structural memory effect of layered double hydroxides (LDHs) has been rarely reported. In this study, five kinds of calcined LDHs (CLDHs) were synthesized and used as adsorbents for the sorption of selenium with or without silicate, under the initial pH 10 and 13, respectively, characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), infrared spectroscopy (IR), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and N2 adsorption-desorption isotherm. The results indicated that silicate can significantly affect the phase transformation of CLDHs, and the sorption amounts of selenite and selenate dramatically decreased in the presence of silicate. Specifically, silicate can react with MgO and Al2O3 in CLDHs to generate magnesium silicate hydrate and geopolymer-like substance which were covered on the surface of particles, blocking the hydroxylation of metal oxides. However, higher pH suppressed the interaction between MgO and silicate and enhanced the formation of geopolymer-like substance, which promoted the regeneration of LDHs. Al in CLDHs plays a critical role in the regeneration of LDHs. Besides, the ternary oxides (CLDH-2, Mg2Al0.75Fe0.25-oxide; CLDH-3, Mg2Al0.5Fe0.5-oxide) possessed larger specific surface areas (127.7 and 158.2 m2/g) and consequently presented more resistance to the effect of silicate..
27. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Shigeto Kuroiwa, Yuji Aoki, Effect of H2O2 and potassium amyl xanthate on separation of enargite and tennantite from chalcopyrite and bornite using flotation, Minerals Engineering, 10.1016/j.mineng.2020.106371, 152, 2020.06, Effect of oxidation treatment using hydrogen peroxide (H2O2) on the floatability of copper sulfide minerals (i.e., chalcopyrite and bornite) and arsenic-bearing copper minerals (i.e., tennantite and enargite) is reported in this study. Pure mineral flotation shows that the floatability of each mineral significantly decreases after the oxidation treatment. Interestingly, flotation of mixed mineral of copper sulfide and arsenic-bearing copper minerals shows that enargite and tennantite exhibit a higher floatability compared to chalcopyrite and bornite after the oxidation treatment followed by the addition of potassium amyl xanthate (PAX). These flotation results indicate a possibility for selective flotation of copper sulfide and arsenic-bearing copper minerals. Indeed, bench-scale flotation tests show that the oxidation treatment using H2O2 and the addition of PAX can deliver a satisfying separation of copper sulfide and arsenic-bearing copper minerals. Difference oxidation products (i.e., CuO, Cu(OH)2, CuSO4, FeOOH, and Fe2(SO4)3) on each mineral surface are likely the cause of this different flotation behavior. Furthermore, these oxidation products may affect the adsorption amount of PAX on each mineral. Indeed, the adsorption tests show that PAX is adsorbed more on tennantite, bornite, and enargite compared to chalcopyrite owing to the formation of CuSO4 and Cu(OH)2 on the mineral surfaces under oxidizing conditions. A possible mechanism is proposed in this study to explain the selective flotation behavior of mixed minerals..
28. Quanzhi Tian, Binglin Guo, Chitiphon Chuaicham, Keiko Sasaki, Mechanism analysis of selenium (VI) immobilization using alkaline-earth metal oxides and ferrous salt, Chemosphere, 10.1016/j.chemosphere.2020.126123, 248, 2020.06, The immobilization of selenate (SeO42–) using metal oxides (CaO and MgO) and ferrous salt as the immobilization reagents were examined by the leaching test and solid-phase analysis via XRD, XAFS, TGA, and XPS. The results indicated that nearly all of SeO42– was reduced to SeO32– in the CaO-based reaction within 7 days. Then, the generated SeO32– was mainly sorbed onto the iron-based minerals (Fe2O3 and FeOOH) through the formation of both bidentate mononuclear edge-sharing (1E) and monodentate mononuclear corner-sharing (1V) inner-sphere surface complexes, suggested by PHREEQC simulation and EXAFS analysis. Differently, less amount of SeO42– (approximately 45.50%) was reduced to SeO32– for the MgO-based reaction. However, if the curing time increases to a longer time (more than 7 days), the further reduction could occur because there are still Fe(II) species in the matrix. As for the associations of Se in the solid residue, most of the selenium (SeO32– and SeO42–) was preferentially distributed onto the Mg(OH)2 through outer-sphere adsorption. Definitely, this research can provide a deep understanding of the immobilization of selenium using alkaline-earth metal oxide related materials and ferrous substances..
29. Subbaiah Muthu Prabhu, Keiko Sasaki, S. SD Elanchezhiyan, G. Paruthimal Kalaignan, Chang Min Park, Self-tuning tetragonal zirconia-based bimetallic nano(hydr)oxides as superior and recyclable adsorbents in arsenic-tolerant environment
Template-free in and ex situ synthetic methods, stability, and mechanisms, Chemical Engineering Journal, 10.1016/j.cej.2020.124573, 390, 2020.06, In this study, we aimed to decorate nano-ZrO2 on LaOx to enhance the architectural stability of LaOx for the uptake of both arsenate and arsenite in single solutions. LaOx was obtained as lanthanum methanoate (LaMe) from a simple solvothermal reaction of lanthanum and benzoic acid. The leaving group of formic acid was used as a reducing agent to grow ZrO2 over LaOx, which resulted in a nanocomposite denoted as ZrO2@x%LaMe. The de-arsenic behavior of this composite was compared with that of one-pot-synthesized La-ZrO2 and ZrO2@x%La(OH)3, with La(OH)3 being obtained commercially. Powder X-ray diffraction patterns showed that the ZrO2 structure was transformed from monoclinic to tetragonal during the formation of ZrO2@x%LaMe, La-ZrO2, and ZrO2@x%La(OH)3. Among the synthesized nano-bimetallic composites, ZrO2@50%LaMe exhibited the highest adsorption densities for both arsenate and arsenite due to the uniform distribution of ZrO2 over the LaOx surface resulted in a larger Brunauer–Emmett–Teller specific surface area and a higher zeta potential charge. The synthesized nanocomposites were reused several times with the aid of 0.1 M HNO3 for maximizing the uptake of both arsenate and arsenite from water. Selectivity and the stability (pH) studies indicated that the nanocomposites were highly selective and showed zero-dissolution behavior, respectively. The results of this study suggested that these nanocomposites could be used as alternatives for many La-based adsorbent materials in practical applications..
30. Binglin Guo, Yuta Kamura, Paulmanickam Koilraj, Keiko Sasaki, Co-sorption of Sr2+ and SeO42- as the Surrogate of Radionuclide by Alginate-encapsulated Graphene Oxide-Layered Double Hydroxide Beads, Environmental Research, in press., 2020.05.
31. Kojo T. Konadu, Kojo, Diego M. M. Flores, Ryotaro Sakai, Robert J. Huddy, Susan T. L. Harrison, Takashi Kaneta, Keiko Sasaki, Biological pretreatment of carbonaceous matter in double refractory gold ores: a review and some future considerations, Hydrometallurgy, accepted, 2020.05.
32. Quanzhi Tian, Binglin Guo, Keiko Sasaki, Addition of calcined hydrotalcite into geopolymer pastes activated by different alkaline solutions for immobilization of selenium: influence and mechanism analysis, J. Hazard. Mater., https://doi.org/10.1016/j.jhazmat.2019.121880, 387, 121994, 2020.05.
33. Seonyi Namgung, Binglin Guo, Keiko Sasaki, Sang Soo Lee, Giehyeon Lee, Macroscopic and microscopic behaviors of Mn(II) (ad)sorption to goethite with the effects of dissolved carbonates under anoxic conditions, Geochimica et Cosmochimica Acta, 10.1016/j.gca.2020.03.036, 277, 300-319, 2020.05, Manganese and its compounds have been extensively studied because of their far-reaching roles in a wide range of biogeochemical processes in natural systems. The (ad)sorption behavior of Mn(II), however, is poorly understood despite its important role as the primary reaction step for surface-catalyzed Mn(II) oxidation that is the principal abiotic process forming various Mn (oxyhydr)oxides in nature. Here, we systematically examined Mn(II) (ad)sorption to one of the most common natural sorbents, goethite, in oxygen- and carbonate-free systems. Traditional sorption edge and isotherm experiments were conducted by varying sorbate-to-sorbent ratio (0.027–15 μmol∙m−2) and solution pH (pH 5.0–9.0). The effects of dissolved carbonates on Mn(II) sorption were also assessed in a range of naturally prevalent concentrations (0.5–10 mM NaHCO3). The Mn(II) uptake on goethite followed a typical Langmuir isotherm in the absence of dissolved carbonates, with increasing maximum adsorption capacities (Γmax) from 0.19 at pH 6.5 to 3.4 μmol∙m−2 at pH 9.0. The presence of dissolved carbonates raised the extent of Mn(II) adsorption, which appeared to be directly correspondent to that of the adsorption of dissolved carbonates. Extended X-ray absorption fine structure (EXAFS) analysis indicated that Mn(II) predominantly formed inner-sphere binuclear bidentate surface complexes. Mn(II) uptake became deviated from the Langmuir model and showed a clear indication of surface precipitation when the Mn(II) sorption density (Γ) exceeded a threshold value in a given solution composition. This secondary Mn(II) phase was identified as rhodochrosite using X-ray diffraction (XRD) and transmission electron microscope (TEM). Additionally, it would be plausible that a minor fraction of adsorbed Mn(II) coexisted with the secondary rhodochrosite according to a linear combination fitting (LCF) of the X-ray absorption near edge structure (XANES) spectra of Mn reference and samples. These systematic investigations of the macroscopic and microscopic behaviors of Mn(II) (ad)sorption to goethite provide a critical avenue for disentangling surface-catalytic Mn(II) oxidation processes, which ultimately lead to the formation of diverse Mn (oxyhydr)oxides in the environment..
34. Keiko Sasaki, Yoshikazu Hayashi, Takeshi Nakamura, Binglin Guo, Quanzhi Tian, Stabilization of borate by hot isostatic pressing after coprecipitation with hydroxyapatite using MAP, Chemosphere, in press, https://doi.org/10.1016/j.chemosphere.2020.126860, 2020.04.
35. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima; Hajime Miki; Keiko Sasaki, Effect of H2O2 and potassium amyl xanthate on separation of enargite and tennantite from chalcopyrite and bornite using flotation, Minerals Engineering, in press, 2020.04.
36. Seonyi Namgung, Binglin Guo, Keiko Sasaki, Sang Soo Lee, Giehyeon Lee, Macroscopic and microscopic behaviors of Mn(II) (ad)sorption to goethite with the effects of dissolved carbonates under anoxic conditions , Geochimica et Cosmochimica Acta, https://doi.org/10.1016/j.gca.2020.03.036, 277, 300-319, 2020.04.
37. Chitiphon Chuaicham, Sekar Karthikeyan, Radheshyam R. Pawar, Yihuang Xiong, Ismaila Dabo, Bunsho Ohtani, Yoonyoung Kim, Jun Tae Song, Tatsumi Ishihara, Keiko Sasaki, Energy-resolved distribution of electron traps for O/S-doped carbon nitrides by reversed double-beam photoacoustic spectroscopy and the photocatalytic reduction of Cr(vi), Chemical Communications, 10.1039/c9cc09988c, 56, 26, 3793-3796, 2020.04, We report for the first time to our knowledge the identification of heteroatom-doped and undoped C3N4 with the energy-resolved distribution of electron traps (ERDT) near the conduction band bottom position (CBB) using reversed double-beam photoacoustic spectroscopy. The ERDT/CBB pattern is used to classify the type of elemental doping in C3N4, related to photocatalytic efficiency..
38. Quanzhi Tian, Binglin Guo, Keiko Sasaki, Immobilization mechanism of Se oxyanions in geopolymer
Effects of alkaline activators and calcined hydrotalcite additive, Journal of Hazardous Materials, 10.1016/j.jhazmat.2019.121994, 387, 2020.04, Geopolymers have been widely adopted to stabilize the cationic pollutants. However, few studies have focused on the immobilization of anionic species. In this study, the immobilization of SeO32– and SeO42– was explored for the first time using geopolymer activated by different alkaline solutions (NaOH and Na2SiO3) with and without calcined hydrotalcite (CHT), characterized by TCLP, XRD, FTIR, TG, NMR, XAFS, and N2 adsorption-desorption isotherm. Na2SiO3-activated geopolymers without CHT additive showed lower leaching percentages of SeO32– and SeO42– (approximately 10 % and 18 %) than NaOH-activated geopolymers (approximately 58 % and 74 %). It has been proven that electrostatic interaction is the main association mode of SeO32– and SeO42– in both NaOH- and Na2SiO3-activated geopolymers. Hence, compactness plays a vital role in the Se leaching from geopolymer. The addition of CHT reduced the compactnesses of both NaOH- and Na2SiO3-geopolymers. Due to the formation of hydrotalcite, the CHT additive contributed to immobilize SeO32– and SeO42– in NaOH-activated geopolymers. However, this phenomenon was not observed in Na2SiO3-activated geopolymers. Thus, the leaching amount of Se greatly increased from Na2SiO3-activated geopolymers with CHT additive. This study provides new insights on the application of geopolymer to immobilize anionic pollutants..
39. Sekar Karthikeyan, Kassam Ahmed, Amin Osatiashtiani, Adam F. Lee, Karen Wilson, Keiko Sasaki, Ben Coulson, Will Swansborough-Aston, Richard E. Douthwaite, Wei Li, Pompon Dahlia-like Cu2O/rGO Nanostructures for Visible Light Photocatalytic H2 Production and 4-Chlorophenol Degradation, ChemCatChem, 10.1002/cctc.201902048, 12, 6, 1699-1709, 2020.03, Hierarchical Cu2O nanospheres with a Pompon Dahlia-like morphology were prepared by a one-pot synthesis employing electrostatic self-assembly. Nanocomposite analogues were also prepared in the presence of reduced graphene oxide (rGO). Photophysical properties of the hierarchical Cu2O nanospheres and Cu2O/rGO nanocomposite were determined, and their photocatalytic applications evaluated for photocatalytic 4-chlorophenol (4-CP) degradation and H2 production. Introduction of trace (<1 wt %) rGO improves the apparent quantum efficiency (AQE) at 475 nm of hierarchical Cu2O for H2 production from 2.23 % to 3.35 %, giving an increase of evolution rate from 234 μmol.g−1.h−1 to 352 μmol.g−1.h−1 respectively. The AQE for 4-CP degradation also increases from 52 % to 59 %, with the removal efficiency reaching 95 % of 10 ppm 4-CP within 1 h. Superior performance of the hierarchical Cu2O/rGO nanocomposite is attributable to increased visible light absorption, reflected in a greater photocurrent density. Excellent catalyst photostability for >6 h continuous reaction is observed..
40. Chitiphon Chuaicham, Radheshyam Rama Pawar, Sekar Karthikeyen, Bunsho Ohtani , Keiko Sasaki, Fabrication and characterization of ternary sepiolite/g-C3N4/Pd composites for improvement of photocatalytic degradation of ciprofloxacin under visible light irradiation, Journal of Colloid and Interface Science, in press, 2020.02.
41. Ryotaro Sakai, Kojo T. Konadu, Diego M.M. Flores, Susan H. L. Harrison, Keiko Sasaki, Effect of carbonaceous matter on bioleaching of Cu from chalcopyrite ore, Hydrometallurgy, 2020.02.
42. Subbaiah Muthu Prabhu, Keiko Sasaki, S.S D. Elanchezhiyan, G. Paruthimal Kalaignan, Self-tuning tetragonal zirconia-based bimetallic nano(hydr)oxides as superior and recyclable adsorbents in arsenic-tolerant environment: Template-free in and ex situ synthetic methods, stability, and mechanisms, Chemical Engineering Journal, 2020.02.
43. Wuhui Luo, Qidong Huang, Philip Antwi, Binglin Guo, Keiko Sasaki, Synergistic effect of ClO4− and Sr2+ adsorption on alginate-encapsulated organo-montmorillonite beads: Implication for radionuclide immobilization, Journal of Colloid and Interface Science, 560, 2020, 338-348, 2020.02.
44. Quanzhi Tian, Binglin Guo, Chitiphon Chuaicham, Keiko Sasaki, Mechanism analysis of selenium (VI) immobilization using alkalineearth metal oxides and ferrous salt, Chemosphere, https://doi.org/10.1016/j.chemosphere.2020.126123, 248, 126123, 2020.02.
45. Chitiphon Chuaicham, Sekar Karthikeyan, Jun Tae Song, Tatsumi Ishihara, Bunsho Ohtani, Keiko Sasaki, Importance of ZnTiO3 Phase in ZnTi-Mixed Metal Oxide Photocatalysts Derived from Layered Double Hydroxide, ACS Applied Materials and Interfaces, 10.1021/acsami.9b18785, 12, 8, 9169-9180, 2020.02, In this study, ZnTi-mixed metal oxides (ZTM), such as ZnTiO3, were synthesized from ZnTi layered double hydroxides by varying the molar ratio of Zn/Ti, calcination temperatures, and synthesis methods (hydrothermal or reflux). The surface electronic characteristics of ZTM were investigated by the energy-resolved distribution of electron traps (ERDTs) using reversed double-beam photoacoustic spectroscopy. The ZTM samples obtained by conducting hydrothermal synthesis at 500 °C showed similar ERDT patterns independent of the molar ratio of Zn/Ti, although ZnTiO3 phase was not observed in the X-ray diffraction pattern, when the Zn/Ti ratio was high. When the ERDT patterns demonstrated a high electron accumulation level near the conduction band bottom in hydrothermal products at 500 °C, a higher photocatalytic phenol degradation efficiency was observed due to the formation of ZnTiO3 phase. This suggested that the product with the high Zn/Ti molar ratio (Zn/Ti = 6) constituted amorphous ZnTiO3.The enhanced photocatalytic performance of ZTM could be attributed to the heterojunction of electrons among ZnO, TiO2, and ZnTiO3, which enabled electron transfer in the composites, prevented charge recombination, and promoted a wider visible light adsorption by ZnTiO3 phase irrespective of its crystallinity..
46. Wuhui Luo, Qidong Huang, Philip Antwi, Binglin Guo, Keiko Sasaki, Synergistic effect of ClO4 and Sr2+ adsorption on alginate-encapsulated organo-montmorillonite beads
Implication for radionuclide immobilization, Journal of Colloid And Interface Science, 10.1016/j.jcis.2019.10.049, 560, 338-348, 2020.02, Perchlorate (ClO4 ) and pertechnetate (TcO4 ) exhibit similar adsorption characteristics on alkyl quaternary ammonium-modified montmorillonite (Mt), and 99mTcO4 normally coexists with 90Sr2+ in radionuclide-contaminated water. In this study, hexadecyl pyridinium (HDPy)-modified Mt (OMt) was encapsulated in alginate beads to inhibit HDPy release and simultaneously immobilize ClO4 and Sr2+ ions. The release of HDPy was remarkably reduced (78 times) from OMt after alginate encapsulation. Adsorption of ClO4 and Sr2+ on the obtained composite demonstrated synergistic effects, with adsorption capacities reaching 0.542 and 0.484 mmol/g, respectively. Compared to the single-adsorbate system, adsorption capacities of ClO4 and Sr2+ increased significantly. The characterization of solids using X-ray diffraction, Fourier transform infrared spectroscopy, 13C nuclear magnetic resonance, and X-ray photoelectron spectroscopy, as well as the chemical analysis of the aqueous solution, demonstrated that HDPy+–COO disintegration accounted for the adsorption synergy. HDPy was extracted from the Mt interlayer space during the synthesis of OMt/alginate and then partially re-intercalated back after interacting with ClO4 during the adsorption of ClO4 and/or Sr2+. In the binary-adsorbate system, the synergy-induced adsorption capacity was superior to many previously reported adsorbents, implying that OMt/alginate beads can be a promising adsorbent for the remediation of aqueous solutions contaminated with multiple radionuclides..
47. Quanzhi Tian, Binglin Guo, Keiko Sasaki, Immobilization mechanism of Se oxyanions in geopolymer: Effects of alkaline activators and calcined hydrotalcite additive, J. Hazard. Mater., doi.org/10.1016/j.jhazmat.2019.121994 , 2020.01.
48. Chitiphon Chuaicham, Radheshyam R Pawar, Karthikeyen Sekar, Yihuang Xiong, Ismaila Dabo, Bunsho Ohtani, Keiko Sasaki, Energy-resolved distribution of electron traps for O/S-doped carbon nitrides by reversed double-beam photoacoustic spectroscopy and the photocatalytic reduction of Cr(VI), Chemical Communications, in press., 2020.01.
49. Chitiphon Chuaicham, Sekar Karthikeyen, Jun Tae Song, Tatsumi Ishihara, Bunsho Ohtani, Keiko Sasaki, Importance of ZnTiO3 phase in ZnTi-mixed metal oxide photocatalysts derived from layered double hydroxide, ACS Applied Materials & Interfaces, in press., https://doi.org/10.1021/acsami.9b18785, 2019.12.
50. Sekar Karthikeyan,Kassam Ahmed, Amin Osatiashtiani, Adam F. Lee, Karen Wilson, Keiko Sasaki, Ben Coulson, Will Swansborough-Aston, Richard E. Douthwaite, and Wei Li, Pompon Dahlia-like Cu2O/rGO nanostructures for visible light photocatalytic H2 production and 4-chlorophenol degradation, Chem Cat Chem, doi.org/10.1002/cctc.201902048, in press, 2019.12, Hierarchical Cu2O nanospheres with a Pompon Dahlia-like
morphology were prepared by a one-pot synthesis employing
electrostatic self-assembly. Nanocomposite analogues were also
prepared in the presence of reduced graphene oxide (rGO).
Photophysical properties of the hierarchical Cu2O nanospheres and
Cu2O/rGO nanocomposite were determined, and their photocatalytic
applications evaluated for photocatalytic 4-chlorophenol (4-CP)
degradation and H2 production. Introduction of trace (<1 wt%) rGO
improves the apparent quantum efficiency (AQE) at 475 nm of
hierarchical Cu2O for H2 production from 2.23 % to 3.35 %, giving an
increase of evolution rate from 234 μmol.g-1.h-1 to 352 μmol.g-1.h-1
respectively. The AQE for 4-CP degradation also increases from 52 %
to 59 %, with the removal efficiency reaching 95 % of 10 ppm 4-CP
within 1 h. Superior performance of the hierarchical Cu2O/rGO
nanocomposite is attributable to increased visible light absorption,
reflected in a greater photocurrent density. Excellent catalyst
photostability for >6 h continuous reaction is observed.
.
51. Sekar Karthikeyan, Chitiphon Chuaicham, Radheshyam R. Pawar, Keiko Sasaki, Wei Li, Adam F. Lee and Karen Wilson, Template free mild hydrothermal synthesis of core–shell Cu2O(Cu)@CuO visible light photocatalysts for N-acetyl-para-aminophenol degradation, Journal of Materials Chemistry A, 10.1039/c9ta07009e, 20737-20777, 7, 2019.12.
52. Quanzhi Tian, K. Sasaki, A novel composite of layered double hydroxide/geopolymer for co-immobilization of Cs+ and SeO4 2− from aqueous solution, Science of the Total Environment, 10.1016/j.scitotenv.2019.133799, 695, 2019.12, Geopolymers are always considered as promising materials for the treatment of radioactive wastes. In order to extend the application of geopolymer to the immobilization of anionic species, a novel composite of layered double hydroxide/geopolymer (LDH/GEO) was synthesized and applied for cosorption of Cs+ and SeO4 2−. The ability of LDH/GEO to sorb Cs+ was maintained as that of pure GEO, even though the surface of geopolymer was homogeneously covered by the LDH platelets. The sorption of Cs+ onto LDH/GEO composite occurred via ion exchange, which was controlled by particle diffusion. It is different with Cs+ sorption onto pure GEO governed by film diffusion. Therefore, “Pocket diffusion” was proposed for the particle diffusion as the case of LDH/GEO because this kind of diffusion would be restricted in a certain distance around the ring entrance gate due to the amorphous essence of GEO. For SeO4 2− sorption by LDH/GEO, ion-exchange with the interlayer NO3 and surface sorption could be the main mechanisms. Importantly, the sorption speed of SeO4 2− achieved by LDH/GEO composite was much faster than that by pure LDH. In the binary system (Cs++ SeO4 2−), the sorption of Cs+ was slightly suppressed compared to the single system, which might be due to the formation of ion-pair complex of [CsSeO4]. However, it did not have negative effect on the SeO4 2− sorption. In the presence of other cations or anions, the cosorption performances of Cs+ and SeO4 2− were satisfactorily obtained. Furthermore, the Cs+ and SeO4 2- sorption densities were superior to the previously reported values. The combined MgAl-LDH/geopolymer composite could be a promising material for the immobilization of Cs+ and SeO4 2−, and this work would provide guidance for the development of geopolymer-based materials for environmental applications..
53. Shuang Xu; Jiawen Zhao; Qianqian Yu; Xinhong Qiu; Keiko Sasaki, Understanding how specific functional groups in humic acid affect the sorption mechanisms of different calcinated layered double hydroxides
, Chemical Engineering Journal, in press, 2019.11.
54. Shuang Xu, Jiawen Zhao, Qianqian Yu, Xinhong Qiu, Keiko Sasaki, Structure memory effect of layered double hydroxides in the presence of modeled aromatic compounds to natural organic matter, ACS Earth Space Chemistry, 2019.10.
55. Binglin Guo, Yihuang Xiong, Weinan Chen, Sarah A. Saslow, Naofumi Kozai, Toshihiko Ohnuki, Ismaila Dabo, Keiko Sasaki, Spectroscopic and First-Principles Investigations of Iodine Species Incorporation into Ettringite: Implications for Iodine Migration in Cement Waste Forms, J. Hazard. Mater., 10.1016/j.jhazmat.2019.121880, in press, 2019.10.
56. Paulmanickam Koilraj, Rajathsing Kalusulingam, Keiko Sasaki, Arginine and lysine-functionalized layered double hydroxides as efficient sorbents for radioactive Co2+ removal by chelate-facilitated immobilization, Chemical Engineering Journal, 10.1016/j.cej.2019.05.166, 359-369, 2019.10, An increase in heavy metal contamination in aquatic environments require an efficient sorbent for the removal and reuse of toxic elements. We attempted to synthesize arginine/lysine-functionalized MgAl LDHs in one-pot without using any hazardous alkaline reagents. The LDHs produced at lower temperatures showed larger numbers of amino acids on their surfaces, while these are exchanged with CO32− at higher temperatures. The arginine/lysine present on the surface of LDH enhanced the adsorption of Co2+ and showed the highest adsorption capacity of 1.159 and 1.170 mmol/g for the LDHs functionalized with lysine and arginine, respectively. Kinetics studies indicated that the adsorption of Co2+ occurred by multiple mechanisms. The Co2+ adsorption on these amino acid functionalized LDHs occurs by the formation chelation complex with amino acid, which provide better vicinity of Co2+ to basic LDH that facilitating the enhanced immobilization. The sorption of other divalent metal ions on these arginine/lysine functionalized LDHs followed the order of Co2+ > Ni2+ > Mn2+ > Fe3+. The Co2+ forms diamine-like coordination that is stable on the surface of LDH and causes higher sorption densities, while other metals form partial glycine-like coordination that detaches the amino acid from the surface of LDH, thereby leading to lesser sorption capacity. The conversion of anionic LDH in to a cationic sorbent was successfully fabricated by these arginine/lysine-assisted methods and explored for the remediation of Co2+ from aqueous solution..
57. Quanzhi Tian, Shingo Nakama, Keiko Sasaki, Immobilization of cesium in fly ash-silica fume based geopolymers with different Si/Al molar ratios, Science of the Total Environment, 10.1016/j.scitotenv.2019.06.095, 687, 1127-1137, 2019.10, Geopolymers are considered as promising matrixes for waste solidification. However, the effects of the Si/Al molar ratio of geopolymer on the immobilization efficiencies for metal ions have not been fully studied and understood. In the present study, geopolymers with different Si/Al ratios were synthesized from coal fly ash and silica fume. Adsorption tests were conducted to evaluate their immobilization efficiencies for Cs+. The results indicated that geopolymer with low Si/Al ratio could have a better immobilization performance for Cs+ than that with high Si/Al ratio. High Si/Al ratio could contribute to a more compact structure of geopolymer. Each sorption process fitted better with the pseudo-second-order model, and all of them were governed by film diffusion. However, the diffusion mode was gradually closed to particle diffusion with the increase in the Si/Al ratio. Both Langmuir and Freundlich models could well fit the sorption data, and the free energy of each sorption process decreased with the increase in the Si/Al ratio according to D-R equation. The distribution of AlO4 tetrahedron in the geopolymer structure plays a significant role in the immobilization of Cs+. Low Si/Al ratio could result in that more AlO4 tetrahedrons distribute in the small rings (+. However, high Si/Al ratio leads to the distribution of AlO4 tetrahedrons mainly in larger rings (≥eight-member), and this could contribute to the high leaching amount of Cs+. In addition, high-temperature treatment could contribute to the formation of nepheline or pollucite in geopolymer matrix. These minerals locked Cs+ in their structures, and the leaching amount of Cs+ was reduced correspondingly from high levels (26.36%, 27.26%, and 66.92%) to very low levels (0.67%, 0.53%, and 0.95%)..
58. Paulmanickam Koilraj, Rajathsing Kalusulingam, Keiko Sasaki, Arginine and lysine-functionalized layered double hydroxides as efficient sorbents for radioactive Co2+ removal by chelate-facilitated immobilization, Chemical Engineering Journal, 10.1016/j.cej.2019.05.166, 359-369, 2019.10, An increase in heavy metal contamination in aquatic environments require an efficient sorbent for the removal and reuse of toxic elements. We attempted to synthesize arginine/lysine-functionalized MgAl LDHs in one-pot without using any hazardous alkaline reagents. The LDHs produced at lower temperatures showed larger numbers of amino acids on their surfaces, while these are exchanged with CO32− at higher temperatures. The arginine/lysine present on the surface of LDH enhanced the adsorption of Co2+ and showed the highest adsorption capacity of 1.159 and 1.170 mmol/g for the LDHs functionalized with lysine and arginine, respectively. Kinetics studies indicated that the adsorption of Co2+ occurred by multiple mechanisms. The Co2+ adsorption on these amino acid functionalized LDHs occurs by the formation chelation complex with amino acid, which provide better vicinity of Co2+ to basic LDH that facilitating the enhanced immobilization. The sorption of other divalent metal ions on these arginine/lysine functionalized LDHs followed the order of Co2+ > Ni2+ > Mn2+ > Fe3+. The Co2+ forms diamine-like coordination that is stable on the surface of LDH and causes higher sorption densities, while other metals form partial glycine-like coordination that detaches the amino acid from the surface of LDH, thereby leading to lesser sorption capacity. The conversion of anionic LDH in to a cationic sorbent was successfully fabricated by these arginine/lysine-assisted methods and explored for the remediation of Co2+ from aqueous solution..
59. Quanzhi Tian, Shingo Nakama, Keiko Sasaki, Immobilization of cesium in fly ash-silica fume based geopolymers with different Si/Al molar ratios, Science of the Total Environment, 10.1016/j.scitotenv.2019.06.095, 687, 1127-1137, 2019.10, Geopolymers are considered as promising matrixes for waste solidification. However, the effects of the Si/Al molar ratio of geopolymer on the immobilization efficiencies for metal ions have not been fully studied and understood. In the present study, geopolymers with different Si/Al ratios were synthesized from coal fly ash and silica fume. Adsorption tests were conducted to evaluate their immobilization efficiencies for Cs+. The results indicated that geopolymer with low Si/Al ratio could have a better immobilization performance for Cs+ than that with high Si/Al ratio. High Si/Al ratio could contribute to a more compact structure of geopolymer. Each sorption process fitted better with the pseudo-second-order model, and all of them were governed by film diffusion. However, the diffusion mode was gradually closed to particle diffusion with the increase in the Si/Al ratio. Both Langmuir and Freundlich models could well fit the sorption data, and the free energy of each sorption process decreased with the increase in the Si/Al ratio according to D-R equation. The distribution of AlO4 tetrahedron in the geopolymer structure plays a significant role in the immobilization of Cs+. Low Si/Al ratio could result in that more AlO4 tetrahedrons distribute in the small rings (+. However, high Si/Al ratio leads to the distribution of AlO4 tetrahedrons mainly in larger rings (≥eight-member), and this could contribute to the high leaching amount of Cs+. In addition, high-temperature treatment could contribute to the formation of nepheline or pollucite in geopolymer matrix. These minerals locked Cs+ in their structures, and the leaching amount of Cs+ was reduced correspondingly from high levels (26.36%, 27.26%, and 66.92%) to very low levels (0.67%, 0.53%, and 0.95%)..
60. Paulmanickam Koilraj, Rajathsing Kalusulingam, Keiko Sasaki, Arginine and lysine-functionalized layered double hydroxides as efficient sorbents for radioactive Co2+ removal by chelate-facilitated immobilization, Chemical Engineering Journal, 10.1016/j.cej.2019.05.166, 359-369, 2019.10, An increase in heavy metal contamination in aquatic environments require an efficient sorbent for the removal and reuse of toxic elements. We attempted to synthesize arginine/lysine-functionalized MgAl LDHs in one-pot without using any hazardous alkaline reagents. The LDHs produced at lower temperatures showed larger numbers of amino acids on their surfaces, while these are exchanged with CO32− at higher temperatures. The arginine/lysine present on the surface of LDH enhanced the adsorption of Co2+ and showed the highest adsorption capacity of 1.159 and 1.170 mmol/g for the LDHs functionalized with lysine and arginine, respectively. Kinetics studies indicated that the adsorption of Co2+ occurred by multiple mechanisms. The Co2+ adsorption on these amino acid functionalized LDHs occurs by the formation chelation complex with amino acid, which provide better vicinity of Co2+ to basic LDH that facilitating the enhanced immobilization. The sorption of other divalent metal ions on these arginine/lysine functionalized LDHs followed the order of Co2+ > Ni2+ > Mn2+ > Fe3+. The Co2+ forms diamine-like coordination that is stable on the surface of LDH and causes higher sorption densities, while other metals form partial glycine-like coordination that detaches the amino acid from the surface of LDH, thereby leading to lesser sorption capacity. The conversion of anionic LDH in to a cationic sorbent was successfully fabricated by these arginine/lysine-assisted methods and explored for the remediation of Co2+ from aqueous solution..
61. Quanzhi Tian, Shingo Nakama, Keiko Sasaki, Immobilization of cesium in fly ash-silica fume based geopolymers with different Si/Al molar ratios, Science of the Total Environment, 10.1016/j.scitotenv.2019.06.095, 687, 1127-1137, 2019.10, Geopolymers are considered as promising matrixes for waste solidification. However, the effects of the Si/Al molar ratio of geopolymer on the immobilization efficiencies for metal ions have not been fully studied and understood. In the present study, geopolymers with different Si/Al ratios were synthesized from coal fly ash and silica fume. Adsorption tests were conducted to evaluate their immobilization efficiencies for Cs+. The results indicated that geopolymer with low Si/Al ratio could have a better immobilization performance for Cs+ than that with high Si/Al ratio. High Si/Al ratio could contribute to a more compact structure of geopolymer. Each sorption process fitted better with the pseudo-second-order model, and all of them were governed by film diffusion. However, the diffusion mode was gradually closed to particle diffusion with the increase in the Si/Al ratio. Both Langmuir and Freundlich models could well fit the sorption data, and the free energy of each sorption process decreased with the increase in the Si/Al ratio according to D-R equation. The distribution of AlO4 tetrahedron in the geopolymer structure plays a significant role in the immobilization of Cs+. Low Si/Al ratio could result in that more AlO4 tetrahedrons distribute in the small rings (+. However, high Si/Al ratio leads to the distribution of AlO4 tetrahedrons mainly in larger rings (≥eight-member), and this could contribute to the high leaching amount of Cs+. In addition, high-temperature treatment could contribute to the formation of nepheline or pollucite in geopolymer matrix. These minerals locked Cs+ in their structures, and the leaching amount of Cs+ was reduced correspondingly from high levels (26.36%, 27.26%, and 66.92%) to very low levels (0.67%, 0.53%, and 0.95%)..
62. Paulmanickam Koilraj, Rajathsing Kalusulingam, Keiko Sasaki, Arginine and lysine-functionalized layered double hydroxides as efficient sorbents for radioactive Co2+ removal by chelate-facilitated immobilization, Chemical Engineering Journal, 10.1016/j.cej.2019.05.166, 359-369, 2019.10, An increase in heavy metal contamination in aquatic environments require an efficient sorbent for the removal and reuse of toxic elements. We attempted to synthesize arginine/lysine-functionalized MgAl LDHs in one-pot without using any hazardous alkaline reagents. The LDHs produced at lower temperatures showed larger numbers of amino acids on their surfaces, while these are exchanged with CO32− at higher temperatures. The arginine/lysine present on the surface of LDH enhanced the adsorption of Co2+ and showed the highest adsorption capacity of 1.159 and 1.170 mmol/g for the LDHs functionalized with lysine and arginine, respectively. Kinetics studies indicated that the adsorption of Co2+ occurred by multiple mechanisms. The Co2+ adsorption on these amino acid functionalized LDHs occurs by the formation chelation complex with amino acid, which provide better vicinity of Co2+ to basic LDH that facilitating the enhanced immobilization. The sorption of other divalent metal ions on these arginine/lysine functionalized LDHs followed the order of Co2+ > Ni2+ > Mn2+ > Fe3+. The Co2+ forms diamine-like coordination that is stable on the surface of LDH and causes higher sorption densities, while other metals form partial glycine-like coordination that detaches the amino acid from the surface of LDH, thereby leading to lesser sorption capacity. The conversion of anionic LDH in to a cationic sorbent was successfully fabricated by these arginine/lysine-assisted methods and explored for the remediation of Co2+ from aqueous solution..
63. Wuhui Luo, Qidong Huang, Philip Antwi, Binglin Guo, Keiko Sasaki, Synergistic effect of ClO4− and Sr2+ adsorption on alginate-encapsulated orga-no-montmorillonite beads: Implication for radionuclide immobilization, Journal of Colloid and Interface Science, doi.org/10.1016/j.jcis.2019.10.049, 2019.10.
64. Shuang Xu, Jiawen Zhao, Qianqian Yu, Xinhong Qiu, Keiko Sasaki, Effect of Natural Organic Matter Model Compounds on the Structure Memory Effect of Different Layered Double Hydroxides, ACS Earth and Space Chemistry, 10.1021/acsearthspacechem.9b00175, 3, 10, 2175-2189, 2019.10, The structural transformation of layered double hydroxides (LDHs) plays an important role in a variety of natural environmental behaviors. As one of the important ways of structure transformation in LDHs, the structure memory effect closely interacted with humic acid (HA). However, the role of functional groups in HA is unclear because its structure is relatively complex. Therefore, seven representative small molecules of single or double aromatic compounds were selected to explore their influence on the regeneration of different LDHs, thereby revealing key function groups in HA. As a result, ortho-benzene compounds could more effectively affect the regeneration of LDHs than other model compounds. For these compounds, the aliphatic chain length and aromatic ring size have little effect on regeneration of LDHs. However, increasing the number of carboxyl or hydroxyl groups affected the results, although all of them accelerated the regeneration rate of LDHs. Additionally, LDHs during the regeneration have a positive adsorption effect on both o-carboxyl and o-hydroxyl aromatic compounds; however, they have shown different effects on the regeneration of LDHs. Phthalic acid revealed no effect on the structure and crystallinity of regenerated LDH, while catechol inhibited the regeneration process and decreased the crystallinity of regenerated LDHs. The effects of o-hydroxyl aromatic compounds, such as catechol, are also dependent upon the type of LDHs. They have an inhibitory effect on the crystallinity of the regenerated Mg-LDH within a short time or with a high concentration but have no effect on its morphology. Although o-hydroxyl aromatic compounds have no effect on the crystallinity of regenerated Ca-LDH, the crystal growth was suppressed. This is due to the difference in the regeneration processes between two LDHs. These results provide a more detailed theoretical basis for understanding the influence of HA on the structural transformation of LDHs or even other minerals, such as hydroxides, in the environment..
65. Kojo T. Konadu, Susan T.L. Harrison, Kwadwo Osseo-Asare, Keiko Sasaki, Transformation of the carbonaceous matter in double refractory gold ore by crude lignin peroxidase released from the white-rot fungus, International Biodeterioration and Biodegradation, 10.1016/j.ibiod.2019.104735, 143, 2019.09, Sulfides and carbonaceous matter in double refractory gold ore (DRGO) were bio-treated sequentially using an iron-oxidizing archaeon Acidianus brierleyi followed by lignin peroxidase-dominating crude enzymes released from the white-rot fungus Phanerochaete chrysosporium to significantly improve gold recovery from 24% to 92%. Transformation of the carbonaceous matter in the sequential bio-treatment was interpreted with Quantitative Evaluation of Materials by Scanning Electron Microscopy (QEMSCAN), Raman spectroscopy and three-dimensional fluorescence spectrometry. Firstly, microbiological sulfide oxidation did not affect carbonaceous matter but decreased the arsenic content in the solid residue, facilitating the following enzymatic reaction. Next, the crude enzymes predominantly decomposed the defect-bearing graphitic carbon into humic-like substances. The humic-like substances were not completely soluble under pH 4 but were instead retained in the solid residue as a part of a newly formed carbonaceous aluminosilicate (C–Si–Al) phase. Due to a wide pKa range of humic-like substances, it is proposed that at pH 4, electrostatic interaction between humic substances and illite, with and without heavy metals, might have enabled the agglomeration of fine aluminosilicate particles. Some gold grains trapped in C–Si–Al agglomerates were released by the dissolution of humic-like substances in 1 M NaOH, resulting in a further increase in gold recovery of approximately 15%..
66. Karthikeyan Sekar; Chitiphon Chuaicham,; Radheshyam Pawar,; Keiko Sasaki, Wei Li, Adam Lee, Karen Wilson, Template free mild hydrothermal synthesis of core-shell Cu2O(Cu)@CuO visible light photocatalysts for N-acetyl-para-aminophenol degradation, J. Mater. Chem. A, 7, 20767-20777., 2019.09.
67. Sekar Karthikeyan, Chitiphon Chuaicham, Radheshyam R Pawar, Keiko Sasaki, Wei Li, Adam F. Lee, Karen Wilson, Template free mild hydrothermal fabrication of size-controlled core-shell CuO@Cu2O visible light photocatalyst, structural stability and their interfacial charge transfer mechanistic investigation, J. Material Chemistry A, 2019.08, Solar photocatalytic processes are a promising approach to environmental remediation, however their implementation requires improvements in visible light harvesting and conversion and a focus on low cost, Earth abundant materials. Semiconducting copper oxides are promising visible light photocatalysts for solar fuels and wastewater depollution. Here we report the mild, hydrothermal (template-free) synthesis of core-shell Cu2 0(Cu)@Cu0 photocatalytic architectures for the visible light photocatalytic degradation of N-acetyl-para-aminophenol (APAP). Hollow and rattle-like core-shell nanosphere aggregates with diameters between 200 nm and 2.5 µm formed under different synthesis conditions; all comprised an inner Cu2 0 shell, formed of 10-50 nm nanoparticles、surrounded by a protective corona of CuO nanoparticles. High reductant and structure-directing agent concentrations promoted the formation of a yolk-like Cu2 0/Cu core, associated with improved photophysical properties, notably a high oxidation potential and suppressed charge carrier recombination, that correlated with the highest apparent quantum efficiency (8%) and rate of APAP removal (7 µmol g―1 min―1). Trapping experiments demonstrated hydroxyl radicals were the primary active species responsible for APAP oxidation to quinones and short chain carboxylic acids. Rattle-like core-shell Cu2 0/Cu@Cu0 nanospheres exhibited excellent physiochemical stability and recyclability for APAP photocatalytic degradation.
68. Subbaiah Muthu Prabhu, Radheshyam Rama Pawar, Keiko Sasaki, Chang Min Park, A mechanistic investigation of highly stable nano ZrO 2 decorated nitrogen-rich azacytosine tethered graphene oxide-based dendrimer for the removal of arsenite from water, Chemical Engineering Journal, 10.1016/j.cej.2019.03.277, 1474-1484, 2019.08, We focused to synthesize graphene oxide-polyamidoamine dendrimer, up to 2nd generation, (GO-gen2) via a grafting method and the tethered groups were further covalently functionalized with a nitrogen-rich of an aromatic triazine ring of 5-azacytosine (Aza). Zirconia nanoparticles (ZrO 2 ) has been identified as promising material for removal of AsO 3 3− from water, however, its practical applicability is hindered due to its nanosize. Hence, ZrO 2 was successfully decorated through biomolecule assist on GO-gen2-Aza dendrimer. Various amounts of GO-gen2-Aza were used as stable supports to develop the nanocomposites with ZrO 2 . Then, the adsorption efficiency of highly toxic AsO 3 3− on developed composites was investigated for water treatment. The synthesized GO-dendrimer composites were characterized well before and after adsorption of AsO 3 3− using FTIR, PXRD, SEM, XPS, TGA, TEM and BET analysis. Particle size distribution of ZrO 2 revealed the peak top at 28 nm by zeta potential measurement. During synthesis, the GO sheets of composite were laminated by incorporation of ZrO 2 nanoparticles. The results of the batch experiments showed that ZrO 2 @2%GO-gen2-Aza dendrimer had higher adsorption density of AsO 3 3− than that of other developed forms of dendrimer composites. Langmuir equation well described the adsorption isotherm with the maximum adsorption capacity of 1.075 mmol/g. In addition, the enhanced AsO 3 3− adsorption density on ZrO 2 surface of ZrO 2 @x%GO-gen2-Aza, in which the GO-sheets were delaminated, resulting more ZrO 2 was dispersed homogeneously in the GO-sheets for maximum uptake of AsO 3 3− from water, confirmed by PXRD patterns. These results suggested that the developed GO-based dendrimer materials can be utilised for the practical remediation of toxic AsO 3 3− and other similar types of toxic ions, selenite, phosphate and fluoride from the contaminated water..
69. Quanzhi Tian, Keiko Sasaki, Application of fly ash-based materials for stabilization/solidification of cesium and strontium, Environmental Science and Pollution Research, 10.1007/s11356-019-05612-1, 26, 23, 23542-23554, 2019.08, Coal fly ash, as a solid waste produced from coal-fired power plants, was recycled for synthesis of zeolite A and geopolymer which were used for stabilization/solidification of Cs+ and Sr2+ from aqueous solutions. Specifically, the sorption data was successfully fitted by kinetic and thermodynamic models. The microstructure changes of zeolite A after loading Cs+ and Sr2+ were explored using XRD, FTIR, Raman, TG-DTA, and N2 adsorption/desorption isotherm. The solidification of the spent zeolites using geopolymer was conducted and evaluated. It was found that pseudo-second sorption mechanism was predominant and, according to the Boyd equation, film diffusion seemed to govern the sorption process. The maximum sorption capacities on Cs+ and Sr2+ based on Langmuir model were 2.12 and 1.93 mmol/g, respectively. During ion exchange with Cs+ and Sr2+, Cs+ was inclined to go through the window to occupy the position of eight-member ring, while the Sr2+ was more likely to replace the Na+ in the six-member ring, thereby easily leading to the different changes of zeolite structure. In addition, geopolymer could be a promising matrix for the treatment of radioactive waste because the leaching fraction greatly decreased after solidification by geopolymer. Therefore, the recycling of coal fly ash for radioactive waste disposal could achieve the concept of disposal waste with waste and recycling, which could greatly contribute to the sustainable development of society..
70. Subbaiah Muthu Prabhu, Radheshyam Rama Pawar, Keiko Sasaki, Chang Min Park, A mechanistic investigation of highly stable nano ZrO 2 decorated nitrogen-rich azacytosine tethered graphene oxide-based dendrimer for the removal of arsenite from water, Chemical Engineering Journal, 10.1016/j.cej.2019.03.277, 1474-1484, 2019.08, We focused to synthesize graphene oxide-polyamidoamine dendrimer, up to 2nd generation, (GO-gen2) via a grafting method and the tethered groups were further covalently functionalized with a nitrogen-rich of an aromatic triazine ring of 5-azacytosine (Aza). Zirconia nanoparticles (ZrO 2 ) has been identified as promising material for removal of AsO 3 3− from water, however, its practical applicability is hindered due to its nanosize. Hence, ZrO 2 was successfully decorated through biomolecule assist on GO-gen2-Aza dendrimer. Various amounts of GO-gen2-Aza were used as stable supports to develop the nanocomposites with ZrO 2 . Then, the adsorption efficiency of highly toxic AsO 3 3− on developed composites was investigated for water treatment. The synthesized GO-dendrimer composites were characterized well before and after adsorption of AsO 3 3− using FTIR, PXRD, SEM, XPS, TGA, TEM and BET analysis. Particle size distribution of ZrO 2 revealed the peak top at 28 nm by zeta potential measurement. During synthesis, the GO sheets of composite were laminated by incorporation of ZrO 2 nanoparticles. The results of the batch experiments showed that ZrO 2 @2%GO-gen2-Aza dendrimer had higher adsorption density of AsO 3 3− than that of other developed forms of dendrimer composites. Langmuir equation well described the adsorption isotherm with the maximum adsorption capacity of 1.075 mmol/g. In addition, the enhanced AsO 3 3− adsorption density on ZrO 2 surface of ZrO 2 @x%GO-gen2-Aza, in which the GO-sheets were delaminated, resulting more ZrO 2 was dispersed homogeneously in the GO-sheets for maximum uptake of AsO 3 3− from water, confirmed by PXRD patterns. These results suggested that the developed GO-based dendrimer materials can be utilised for the practical remediation of toxic AsO 3 3− and other similar types of toxic ions, selenite, phosphate and fluoride from the contaminated water..
71. Quanzhi Tian, Keiko Sasaki, Characterizations of calcium silicate hydrates derived from coal fly ash and their mechanisms for phosphate removal, Desalination and Water Treatment, 10.5004/dwt.2019.24135, 156, 78-86, 2019.07, Coal fly ash is an industrial waste generated from the thermal power plant and a large amount of it could be produced annually in the world, which can cause serious environmental problems. Reutilization of coal fly ash could be imperative to alleviate the environmental pressure. Thus, in the present study, coal fly ash was used as silicon source for the synthesis of calcium silicate hydrates (C-S-Hs) though the desilication process. Two kinds of C-S-Hs was synthetized at 100°C and room temperature respectively, with the fixed Ca/Si molar ratio of 1.2, and adopted as the adsorbents for phosphate. The properties of them were characterized using XRD, SEM, FTIR, TG-DTA as well as surface area and pore analysis. Compared to C-S-H synthesized from high temperature, the C-S-H obtained at room temperature possessed high purity and larger surface area. Therefore, synthesis by agitation at room temperature could be an alternative method to produce C-S-H materials from desilication liquid of coal fly ash, and this could save infrastructure cost and energy consumption. Both C-S-H materials have good ability to immobilize phosphate pollutant (higher than 100 mg·g–1). The specific mechanisms of phosphate removal using C-S-H include several steps: Firstly, phosphate ion was immobilized by binding with Ca2+and forming aggregates, and the C-S-H structures were gradually corroded. Eventually, hydroxyapatite was formed after the C-S-H structure was totally destroyed..
72. Kojo T. Konadu, Robert J. Huddy, Susan T.L. Harrison, Kwadwo Osseo-Asare, Keiko Sasaki, Sequential pretreatment of double refractory gold ore (DRGO)with a thermophilic iron oxidizing archeaon and fungal crude enzymes, Minerals Engineering, 10.1016/j.mineng.2019.04.043, 138, 86-94, 2019.07, Double refractory gold ore was sequentially pretreated to oxidize sulfides by thermophilic archaeon Acidianus brierleyi and then to decompose carbonaceous matters using the cell-free spent medium (CFSM)from white-rot fungus Phanerochaete chrysosporium. The pretreatment by A. brierleyi significantly improved the gold recovery from 25% to 77%. Additionally, the crude lignin-degrading enzymes in the CFSM converted the carbonaceous matters into more easily degradable substances, which were removed by alkaline washing, leading to a final gold recovery of 92%. These mineralogical alterations were confirmed by differential thermogravimetric analysis and quantitative evaluation of minerals with scanning electron microscopy. Based on the results, gold grains were mostly liberated after bio-oxidation of sulfides, and in following CFSM treatment, large particles of carbonaceous aluminosilicate were formed from the aggregation of clay minerals, gold grains and with partially decomposed carbonaceous matters acting as binders..
73. Quanzhi Tian, Keiko Sasaki, Characterizations of calcium silicate hydrates derived from coal fly ash and their mechanisms for phosphate removal, Desalination and Water Treatment, 10.5004/dwt.2019.24135, 156, 78-86, 2019.07, Coal fly ash is an industrial waste generated from the thermal power plant and a large amount of it could be produced annually in the world, which can cause serious environmental problems. Reutilization of coal fly ash could be imperative to alleviate the environmental pressure. Thus, in the present study, coal fly ash was used as silicon source for the synthesis of calcium silicate hydrates (C-S-Hs) though the desilication process. Two kinds of C-S-Hs was synthetized at 100°C and room temperature respectively, with the fixed Ca/Si molar ratio of 1.2, and adopted as the adsorbents for phosphate. The properties of them were characterized using XRD, SEM, FTIR, TG-DTA as well as surface area and pore analysis. Compared to C-S-H synthesized from high temperature, the C-S-H obtained at room temperature possessed high purity and larger surface area. Therefore, synthesis by agitation at room temperature could be an alternative method to produce C-S-H materials from desilication liquid of coal fly ash, and this could save infrastructure cost and energy consumption. Both C-S-H materials have good ability to immobilize phosphate pollutant (higher than 100 mg·g–1). The specific mechanisms of phosphate removal using C-S-H include several steps: Firstly, phosphate ion was immobilized by binding with Ca2+and forming aggregates, and the C-S-H structures were gradually corroded. Eventually, hydroxyapatite was formed after the C-S-H structure was totally destroyed..
74. Kojo T. Konadu, Robert J. Huddy, Susan T.L. Harrison, Kwadwo Osseo-Asare, Keiko Sasaki, Sequential pretreatment of double refractory gold ore (DRGO)with a thermophilic iron oxidizing archeaon and fungal crude enzymes, Minerals Engineering, 10.1016/j.mineng.2019.04.043, 138, 86-94, 2019.07, Double refractory gold ore was sequentially pretreated to oxidize sulfides by thermophilic archaeon Acidianus brierleyi and then to decompose carbonaceous matters using the cell-free spent medium (CFSM)from white-rot fungus Phanerochaete chrysosporium. The pretreatment by A. brierleyi significantly improved the gold recovery from 25% to 77%. Additionally, the crude lignin-degrading enzymes in the CFSM converted the carbonaceous matters into more easily degradable substances, which were removed by alkaline washing, leading to a final gold recovery of 92%. These mineralogical alterations were confirmed by differential thermogravimetric analysis and quantitative evaluation of minerals with scanning electron microscopy. Based on the results, gold grains were mostly liberated after bio-oxidation of sulfides, and in following CFSM treatment, large particles of carbonaceous aluminosilicate were formed from the aggregation of clay minerals, gold grains and with partially decomposed carbonaceous matters acting as binders..
75. Kojo T. Konadu, Susan Harrison, Kwadwo Osseo-Asare, Keiko Sasaki, Transformation of the carbonaceous matter in double refractory gold ore by crude lignin peroxidase released from the white-rot fungus, International Biodeterioration & Biodegradation, in press, 2019.06.
76. Quanzhi Tian, Shingo Nakama, Keiko Sasaki, Immobilization of cesium in fly ash-silica fume based geopolymers with different Si/Al molar ratio, Science of the Total Environment, 687, 1127-1137, 687 (2019)1127-1137, 2019.06.
77. Binglin Guo, Shingo Nakama, Quanzhi Tian, Niko Dian Pahlevi, Zhaochu Hu, Keiko Sasaki, Suppression processes of anionic pollutants released from fly ash by various Ca additives, Journal of Hazardous Materials, 10.1016/j.jhazmat.2019.03.036, 474-483, 2019.06, Harmful trace elements, which are initially included in the coal fly ash, have the potential to be leached when coal fly ash comes in contact with water. This causes a risk of pollutant species being released, considering the long lifetime of building structures where coal fly ash was applied. Some Ca additives effectively function to suppress the release of anionic pollutants; however, the detailed suppression processes remains unclear. In this work, the influences of various Ca additives on the released anionic pollutants (B, F, S, As, and Cr) was systematically investigated. According to the comprehensive results of solution data with the solid characterization, the 60% hydroxylated calcined dolomite (HCD 60) was the best Ca additive for the suppression of different anionic pollutants since this Ca source not only simply provides an alkaline reagent but also supplies MgO and Mg(OH) 2 , which affect the phase transformation that accompanies with hydration. The phase transformation occurs from Ca(OH) 2 to ettringite via hydrocalumite, which is the most important suppression processes of released pollutants. The precipitation of Ca salts is another pathway to immobilize these pollutants. In this scheme, MgO and Mg(OH) 2 were proven to enhance the formation of ettringite and hydrocalumite, respectively..
78. Paulmanickam Koilraj, Rajathsing Kalusulingam, Keiko Sasaki, Arginine and lysine-functionalized layered double hydroxides as efficient sorbents for radioactive Co2+ removal by chelate-facilitated immobilization, Chemical Engineering Journal, in press, 2019.05.
79. Subbaiah Muthu Prabhu, Srinivasarao Kancharla, Chang Min Park and Keiko Sasaki, Synthesis of modulator-driven highly stable zirconium-fumarate frameworks and mechanistic investigations of their arsenite and arsenate adsorption from aqueous solutions, RSC CrystEngComm, 10.1039/c8ce01424h, 21, 2320-2332, 2019.05, Here, we synthesized a modulator (benzoic acid (BA))-driven zirconium-fumaric acid (Zr-fum) metal–organic framework (MOF) and investigated in detail the adsorption mechanism of arsenic oxyanions (AsO43−and AsO33−) and their stability before and after adsorption from water. Without the support of the modulator, BA, Zr-fum formed an amorphous MOF due to the occurrence of quick precipitation of both zirconiumand -fum. Various amounts of BA, 0–10 eq. to ZrCl4, were used to control the surface charge on the MOF nanoparticles, which directly corresponds to the colloid stability of the MOF and helps to obtain a defect free
Zr-fum MOF for high uptakes of AsO43− and AsO33− from water. With the concentration of 3 eq. BA, the adsorption capacities of both arsenic oxyanions on the Zr-fum MOF were found to be higher than those on other MOFs. The CHN analysis indicated that the excess of -fum present does not alter the adsorption densities of AsO43− and AsO33− on MOFs in addition to the negligible amount of BA except for the Zr-fum-10 eq. BA MOF where it is present in higher amounts, as confirmed by NMR studies. The physicochemical properties of the synthesized MOFs with/without the modulator support adsorbents before and after the adsorption of AsO43− and AsO33− were extensively characterized using several advanced instrumental techniques. The maximum uptake performance of AsO43− (1.159 mmol g−1) and AsO33− (1.121 mmol g−1) was obtained using the Langmuir adsorption isotherm. The adsorption of both AsO4 3− and AsO3 3− takes place by electrostatic interaction/complexation and ligand exchange with Zr-fum-5 eq. BA. In addition, the Zr-fum-5 eq. BA was recycled up to four times at a sustained efficiency after washing with 0.1 M NaOH. Owing to their high uptake capacities of AsO4 3− and AsO3 3−, the synthesized MOFs are expected to have potential applications as adsorbents for practical applications..
80. Quanzhi Tian, Keiko Sasaki, Application of fly ash-based materials for stabilization/solidification
of cesium and strontium, Environmental Science and Pollution Research, https://doi.org/10.1007/s11356-019-05612-1, doi.org/10.1007/s11356-019-05612-1, 2019.05.
81. Xinhong Qiu, Keiko Sasaki, Shuang Xu, Jiawen Zhao, Double-Edged Effect of Humic Acid on Multiple Sorption Modes of Calcined Layered Double Hydroxides
Inhibition and Promotion, Langmuir, 10.1021/acs.langmuir.8b04196, 35, 19, 6267-6278, 2019.05, Layered double hydroxides (LDHs) are a typical class of anionic clay minerals whose structural memory effect has been widely used in pollutant adsorption. However, the influencing mechanism of humic acid (HA) on the structural memory effect in adsorption is not clear. In this study, HA was extracted from black soil and sediments, and its effect on the structural memory effect of LDHs with different divalent metals was evaluated in adsorption. Borate complexed with HAs and HAs promoted the dissolution of magnesium-calcined LDHs (Mg-CLDH), which enhanced their adsorption rate by Mg-CLDH. However, the adsorbed HA caused a decline in the crystallinity of the regenerated Mg-LDH and an incomplete structural transformation, thereby resulting in decreased adsorption capacity. After the complexation of HAs with borate, the resulting compound was adsorbed on the surface of Zn-CLDH. The adsorption rate of borate was effectively improved in the initial stage, but at the same time slowed down the hydration and structural regeneration of Zn-CLDH. Meanwhile, the surface-adsorbed HAs also prevented borate from entering the newly formed layer inside the particles and led to a significant decrease in adsorption performance. When Ca-CLDH was used to adsorb borate, the process mainly occurred through the formation of ettringite. However, the presence of HAs enhanced the stability of the restructured LDHs and hindered the dissolution of Ca-CLDH and the reaction with B(OH) 4 - to form ettringite during the regeneration process, which severely inhibited the sorption of borate..
82. Subbaiah Muthu Prabhu, Shunsuke Imamura, Keiko Sasaki, Mono-, Di-, and Tricarboxylic Acid Facilitated Lanthanum-Based Organic Frameworks
Insights into the Structural Stability and Mechanistic Approach for Superior Adsorption of Arsenate from Water, ACS Sustainable Chemistry and Engineering, 10.1021/acssuschemeng.8b06489, 7, 7, 6917-6928, 2019.04, In this study, we tried to synthesize lanthanum organic frameworks (MOFs) with the linkers of benzoic acid (BA), 1,4-benzene dicarboxylic acid, and 1,3,5-benzenetricarboxylic acid (BTC), abbreviated as La-BA, La-BDC, and La-BTC, respectively. Interestingly, the BA linker approached La metal to form lanthanum methanoate (La(HCOO)
3
) instead of the La-BA MOF through an acid catalyst amide-hydrolysis mechanism, whereas La-BDC and La-BTC act as MOFs, confirmed by PXRD patterns. Various sophisticated instrumentation techniques such as FTIR, PXRD, XPS, BET, and TGA were utilized to understand the formation of MOF. This is the first report to investigate AsO
4

3-
adsorption and the dissolution behavior of La-BA, La-BDC, and La-BTC in detail using different spectroscopic methods. The maximum AsO
4

3-
adsorption densities obtained from the Langmuir isotherm model were found to be 2.623, 3.891, and 0.280 mmol/g for La-BA, La-BDC, and La-BTC, respectively, where the dose ratio was 1 g/L with the speed of 100 rpm at room temperature. The value for La-BDC was significantly superior to the previously reported adsorbents for AsO
4

3-
to date. The presence of AsO
4

3-
on both La-BA and La-BDC was confirmed by FTIR and XPS As 3d. After adsorption of 2.4 mM AsO
4

3-
, the precipitation mechanism controls the adsorption capacities on La-BA and the ligand exchange mechanism on La-BDC confirmed by solution as well as solid analyses. Sorption kinetic data of AsO
4

3-
followed a pseudo-second-order model, which is consistent with chemisorption involving the possible coordination of AsO
4

3-
on La-BA and La-BDC. These results suggested that the MOF materials can be developed to immobilize arsenic-rich wastewater..
83. Kojo T. Konadu, Robert J. Huddy, Susan T. L. Harrison, Kwadwo Osseo-Asare, Keiko Sasaki, Bio-mineral processing of double refractory gold ore in sequential treatment using a thermophilic archaeon followed by fungal spent medium, Minerals Engineering, 138, 86-94, 2019.03.
84. Quanzhi Tian, Keiko Sasaki, Characterizations of Calcium Silicate Hydrates deprived from Coal Fly Ash and Their Mechanisms for Phosphate Removal, Desalination and Water Treatment, in press, 2019.03.
85. Chitiphon Chuaicham, Radheshyam Pawar, Keiko Sasaki, Dye-sensitized photocatalyst of sepiolite for organic dye degradation, Catalysts, 10.3390/catal9030235, 9, 3, 2019.03, The photocatalytic activity of sepiolite was examined for degradation of several dye compounds under visible light irradiation. Higher adsorption capacities and greater photocatalytic performance of cationic dyes (rhodamine B and methylene blue) were observed on sepiolite, in comparison with anionic dyes (orange II and trypan blue). Superiority in the photocatalytic activity of cationic dyes is attributed to the strong electrostatic attraction and photosensitization properties of cationic dye molecules. Sepiolite has degraded 45.3% rhodamine B within 120 min, which is the greatest photocatalytic degradation efficiency when compared with other dyes. Subsequently, the reusability of spent sepiolite after adsorption of rhodamine B was evaluated by the degradation of trypan blue under the visible light irradiation. The photocatalytic degradation performance of trypan blue by spent sepiolite after adsorption of rhodamine B increased about twice as much as with pristine sepiolite, indicating that the dye-sensitized photocatalytic process could enhance the photocatalytic degradation ability of sepiolite. Through radical scavenger tests, it was found that a superoxide radical is mainly responsible for rhodamine B degradation. The possible mechanism of rhodamine B degradation under visible light irradiation was proposed. The sepiolite could be a potential catalyst for the degradation of organic pollutants in wastewater under solar light. View Full-Text.
86. Quanzhi Tian, Binglin Guo, Shingo Nakama, Li Zhang, Zhaochu Hu, Keiko Sasaki, Reduction of Undesirable Element Leaching from Fly Ash by adding Hydroxylated Calcined Dolomite, Waste Management, 10.1016/j.wasman.2019.01.027, in press, 2019.01.
87. Wuhui Luo, Qidong Huang, Binglin Guo, Keiko Sasaki, Organo-montmorillonite encapsulated in alginate for simultaneous adsorption of ClO4- and Sr2+ from aqueous solutions: Mechanism of synergistic effects and implication for radionuclide immobilization, Journal of Colloid and Interface Science, 2019.01.
88. Srinivasarao Kancharla, Keiko Sasaki, Acid tolerant covalently functionalized graphene oxide for the selective extraction of Pd from high-level radioactive liquid wastes, Journal of Materials Chemistry A, 10.1039/c8ta09849b, 7, 9, 4561-4573, 2019.01, The severely depleting reserves of highly demanded palladium (Pd) induce the growing pressure on its recycling. One of the potential secondary sources of Pd is a high-level liquid waste (HLLW) produced from spent nuclear fuel. HLLW contains several metal ions along with Pd in 3-4 M HNO
3
medium. The preparation of highly acid tolerant and efficient functional materials is a challenging task in the solid phase recovery of noble metals. We have explored covalently functionalized graphene oxide (GO) to overcome this issue. GO was covalently functionalized with 1-(3-aminopropyl)imidazole (ImGO) (N-donor) and 2-methylthiophene (ThpGO) (S-donor) through amide or amine formation at different reactive sites. The prepared materials before and after Pd recovery were thoroughly characterized using a variety of state-of-the-art techniques. Solid-phase extraction experiments revealed that the Pd was recovered with remarkable selectivity from HLLW-like solutions in 3 M HNO
3
using both the functionalized materials. The extraction efficiency was found to be higher than that of any of the solid-state materials reported to date. The sorption of Pd onto ImGO and ThpGO was best expressed by the Freundlich isotherm model. The advantages of the prepared materials are twofold: the first one is the high tolerance to harsh acidic conditions, and the second one is the higher selectivity and efficiency for Pd. The sorption of Pd onto ImGO was achieved by complete anion exchange with the nitrate ion, whereas ThpGO recovered Pd through a co-ordination mechanism. The results demonstrated that the developed covalently functionalized GO was the first choice material for the efficient and selective recovery of Pd..
89. Quanzhi Tian, Keiko Sasaki, Application of fly ash-based geopolymer for removal of cesium, strontium and arsenate from aqueous solutions
Kinetic, equilibrium and mechanism analysis, Water Science and Technology, 10.2166/wst.2019.209, 79, 11, 2116-2125, 2019.01, Geopolymerization is a developing reaction process for the utilization of solid wastes. In the present study, fly ash-based geopolymer and its derivative (Fe(II)-modified geopolymer) were synthesized and characterized using XRD, SEM, FTIR, BET, UV-Vis DRS as well as TG-DTA, and adopted as adsorbents for removal of Csþ and Sr, and AsO3 4 from solutions. Each sorption kinetic was well fitted to the pseudo-second-order model. The sorption of Csþ and Sr onto original geopolymer were better fitted to the Langmuir model. However, the Freundlich model is more befitting for sorption of AsO3 4 onto Fe(II)-modified geopolymer. The free energies calculated from the D-R isotherm indicated that the sorption for Csþ and Sr were dominantly ion exchanges. Ring size plays a decisive role in ion exchanges for both Csþ and Sr. Furthermore, the arrangement of SiO4 and AlO4 tetrahedrons has significant impacts on the ion exchange of Sr. XPS results indicated that a part of Fe in Fe (II)-modified geopolymer had been oxidized to Fe after sorption. Precipitation of FeAsO4 could partially contribute to the arsenate removal from solution. AsO3 4 sorption has also occurred through the formation of inner-sphere complexes via ion exchange reaction, which could be predominantly attached by bidentate linkages..
90. Ahmad T. Yuliansyah, Satoshi Kumagai, Tsuyoshi Hirajima, Keiko Sasaki, Hydrothermal treatment of oil palm biomass in batch and semi-flow reactors, 10th International Conference on Applied Energy, ICAE 2018 Energy Procedia, 10.1016/j.egypro.2019.01.182, 158, 675-680, 2019.01, Oil palm frond and empty fruit bunch (EFB), which were abundant biomass resources found in Indonesia, were hydrothermally-treated using two different types of reactor, e.g. batch and semi-flow reactor. The objective of this research was to make a comparison of product resulted from both types of treatment. Based on the experimental results, it was found that liquefaction of biomass material occurred more effectively in semi-flow reactor. Semi-flow reactor facilitated a higher recovery of several sugar compounds such as xylooligosaccharides and arabinose. On the hand, residual solids from batch treatment had higher theoretical calorific values (18.81 and 18.00 MJ/kg) than those from semi-flow (15.40 and 17.41 MJ/kg, for frond and EFB respectively)..
91. Hajime Miki, T. Hirajima, Y. Muta, G. P.W. Suyantara, Keiko Sasaki, Investigation of reagents for selective flotation on chalcopyrite and molybdenite, 29th International Mineral Processing Congress, IMPC 2018 IMPC 2018 - 29th International Mineral Processing Congress, 1854-1861, 2019.01, Selective flotation of chalcopyrite and molybdenite is continuing problem since its selectivity is not perfect and current NaHS process needs closed system flotation plant because of hydrogen sulfide emission on acidic condition. Some alternative additives investigated as chalcopyrite became hydrophilic and molybdenite kept hydrophobic. XPS analysis indicated chalcopyrite became hydrophilic since iron and copper sulphate, hydroxide was covered on the surface whereas molybdenite kept hydrophobic since only molybdenite can be seen. Flotation experiments of chalcopyrite and molybdenite mixture sample indicated excellent separation that 95% of molybdenite can be recovered as froth and 93% of chalcopyrite can be recovered as sink. Flotation experiments with real bulk flotation concentration indicated similar separation result compared with current NaHS additive system. Possible mechanisms and detailed phenomenon were investigated based on the surface analysis and thermodynamic calculation etc. this alternative additive is easy to handle compared with NaHS since it does not emit effluent gas and commercially preferable..
92. Santisak Kitjanukit, Keiko Sasaki, Naoko Okibe, Production of highly catalytic, archaeal Pd(0) bionanoparticles using Sulfolobus tokodaii, Extremophiles, 10.1007/s00792-019-01106-7, 2019.01, The thermo-acidophilic archaeon, Sulfolobus tokodaii, was utilized for the production of Pd(0) bionanoparticles from acidic Pd(II) solution. Use of active cells was essential to form well-dispersed Pd(0) nanoparticles located on the cell surface. The particle size could be manipulated by modifying the concentration of formate (as electron donor; e-donor) and by addition of enzymatic inhibitor (Cu2+) in the range of 14–63 nm mean size. Since robust Pd(II) reduction progressed in pre-grown S. tokodaii cells even in the presence of up to 500 mM Cl, it was possible to conversely utilize the effect of Cl to produce even finer and denser particles in the range of 8.7–15 nm mean size. This effect likely resulted from the increasing stability of anionic Pd(II)–chloride complex at elevated Cl concentrations, eventually allowing involvement of greater number of initial Pd(0) crystal nucleation sites (enzymatic sites). The catalytic activity [evaluated based on Cr(VI) reduction reaction] of Pd(0) bionanoparticles of varying particle size formed under different conditions were compared. The finest Pd(0) bionanoparticles obtained at 50 mM Cl (mean 8.7 nm; median 5.6 nm) exhibited the greatest specific Cr(VI) reduction rate, with four times higher catalytic activity compared to commercial Pd/C. The potential applicability of S. tokodaii cells in the recovery of highly catalytic Pd(0) nanoparticles from actual acidic chloride leachate was, thus, suggested..
93. Subbaiah Muthu Prabhu, Srinivasarao Kancharla, Chang Min Park, Keiko Sasaki, Synthesis of modulator-driven highly stable zirconium-fumarate frameworks and mechanistic investigations of their arsenite and arsenate adsorption from aqueous solutions, CrystEngComm, 10.1039/C8CE01424H, 21, 14, 2320-2332, 2019.01, Here, we synthesized a modulator (benzoic acid (BA))-driven zirconium-fumaric acid (Zr-fum) metal-organic framework (MOF) and investigated in detail the adsorption mechanism of arsenic oxyanions (AsO43− and AsO33−) and their stability before and after adsorption from water. Without the support of the modulator, BA, Zr-fum formed an amorphous MOF due to the occurrence of quick precipitation of both zirconium and -fum. Various amounts of BA, 0-10 eq. to ZrCl4, were used to control the surface charge on the MOF nanoparticles, which directly corresponds to the colloid stability of the MOF and helps to obtain a defect-free Zr-fum MOF for high uptakes of AsO43− and AsO33− from water. With the concentration of 3 eq. BA, the adsorption capacities of both arsenic oxyanions on the Zr-fum MOF were found to be higher than those on other MOFs. The CHN analysis indicated that the excess of -fum present does not alter the adsorption densities of AsO43− and AsO33− on MOFs in addition to the negligible amount of BA except for the Zr-fum-10 eq. BA MOF where it is present in higher amounts, as confirmed by NMR studies. The physicochemical properties of the synthesized MOFs with/without the modulator support adsorbents before and after the adsorption of AsO43− and AsO33− were extensively characterized using several advanced instrumental techniques. The maximum uptake performance of AsO43− (1.159 mmol g−1) and AsO33− (1.121 mmol g−1) was obtained using the Langmuir adsorption isotherm. The adsorption of both AsO43− and AsO33− takes place by electrostatic interaction/complexation and ligand exchange with Zr-fum-5 eq. BA. In addition, the Zr-fum-5 eq. BA was recycled up to four times at a sustained efficiency after washing with 0.1 M NaOH. Owing to their high uptake capacities of AsO43− and AsO33−, the synthesized MOFs are expected to have potential applications as adsorbents for practical applications..
94. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, The use of Fenton's reagent on selective flotation of chalcopyrite and molybdenite, 29th International Mineral Processing Congress, IMPC 2018 IMPC 2018 - 29th International Mineral Processing Congress, 1862-1871, 2019.01, Hydrogen peroxide (H
2
O
2
) is frequently used as an oxidizing agent in various applications. It has also been reported to reduce the recovery of sulfide minerals. Moreover, the previous work applied H
2
O
2
aqueous solution in selective flotation of chalcopyrite and molybdenite. However, the oxidation method suffered in pilot scale test due to too long conditioning time. Furthermore, the excessive reagent consumption increased the reagent cost, causing the method not economically feasible. Consequently, further improvement is required to reduce the conditioning time and the reagent consumption. The oxidation performance of H
2
O
2
can be improved by using ferrous iron as catalyst, producing a Fenton's reagent which is more powerful oxidizer than the H
2
O
2
itself. Therefore, the effect of Fenton's reagent on the floatability of chalcopyrite and molybdenite was investigated in this study. The flotation test results show that selective flotation of chalcopyrite and molybdenite might be possible at low concentration of H
2
O
2
aqueous solution by adding ferrous iron. Moreover, the conditioning time could be shortened by this improvement. To understand the phenomenon, surface characterization using atomic force microscopy (AFM) along with x-ray photoelectron spectroscopy (XPS) analysis were carried out. The AFM images show that the surface of chalcopyrite was readily covered with mountainous features which alters its hydrophobicity after the oxidation treatment. Meanwhile, the molybdenite surface remained clean and relatively hydrophobic. The XPS results indicate that the mountainous features are various oxidation products (i.e., FeOOH, Fe
2
(SO
4
)
3
, CuO, Cu(OH)
2
). Possible mechanisms of this phenomenon were proposed in this work..
95. Quanzhi Tian, Keiko Sasaki, Structural characterizations of fly ash-based geopolymer after adsorption of various metal ions, Environmental Technology (United Kingdom), 10.1080/09593330.2019.1649469, 2019.01, Geopolymer, an amorphous substance, has been viewed as good adsorbent or catalyst and attracted much attentions from all over the world. In order to achieve the better applications of geopolymer in these fields, a deep understanding of the microstructure of geopolymer would be strongly required. In the present study, geopolymer was synthesized from coal fly ash, and the structural analysis of geopolymer after adsorption of various metal ions (Li+, Cs+, Sr2+ and Co2+) was studied using XRD, SEM-EDX, FTIR, UV-VIS DRS, TG-DTA as well as surface area and pore distribution analysis. Pair distribution function preferably illustrated that geopolymer was successfully prepared from calcined fly ash. Geopolymer possesses different affinities towards various metal ions. After exchanging with other metal ions, the main structure of geopolymer was maintained. Metal ions with a large radius would have greater effect on the existing state and amount of water molecules in geopolymer. Moreover, the specific surface area of geopolymer after exchanging with metal ions decreased as a function of the radius of them. The spectra corresponding to d-d transitions indicated that the Co2+ could be incorporated into the deformed six-member rings or eight-membered rings. It could be deduced that the sites for ion exchange could be different rings or even cavities distributed on the surface layer of geopolymer. Furthermore, the rings distributed in the geopolymer structure were predominant in the 6-, 8-, 10- or even 12-member rings to maintain the structure stability and charge balance with the cations..
96. Shuang Xu, Jiawen Zhao, Qianqian Yu, Xinhong Qiu, Keiko Sasaki, Understanding how specific functional groups in humic acid affect the sorption mechanisms of different calcinated layered double hydroxides, Chemical Engineering Journal, 10.1016/j.cej.2019.123633, 392, 2019.01, Humic acid (HA) can affect the adsorption modes of CLDHs, and change the form of pollutants, making it a key factor when considering CLDHs for practical applications. However, the complicated and uncertain structures of HA make it difficult to explore how they will influence the mechanism, so using simple compounds to simulate the role of different reactive groups in HA necessary to understand how they will interact with the application of CLDHs. It was found that both CLDHs strongly adsorb phthalic acid and catechol. All hydroxyl and carboxyl compounds had a similar promoting effect on the adsorption rate and regeneration rate of Mg-CLDH, which were not affected by the number of functional groups, the length of the aliphatic chain, or the number of the aromatic ring. However, their effects were more significant than that of the HA. While they could make the structure of Mg-LDH stacked and incomplete, just like the HA, they did not damage the crystallinity. In particular, catechol inhibited the regeneration of Mg-CLDH to a certain degree. Since the regeneration process was different from Mg-CLDH, different types of hydroxyl or carboxyl compounds degraded the removal of borate by Ca-CLDH, but promoted the formation of ettringite to some extent, especially benzoic acid and 4-phenylbutyric acid. However, catechol severely inhibited the structural transformation of Ca-CLDH into ettringite. Due to the strong interaction of the HA with the surface of Ca-LDH, the formation of ettringite was hindered, which deteriorated the removal of borate. HA did change the adsorption rate and the regeneration process of CLDHs via different reactive groups, and their effects on various CLDHs were different..
97. Kancharla Srinivasarao, Keiko Sasaki, Acid tolerant covalently functionalized graphene oxide for the selective extraction of Pd from high-level radioactive liquid wastes, Journal of Material Chemistry A, in press, 2018.12, The severely depleting reserves of highly demanded palladium (Pd) induce the growing pressure on its recycling. One of the potential secondary sources of Pd is a high-level liquid waste (HLLW) produced
from spent nuclear fuel. HLLW contains several metal ions along with Pd in 3–4 M HNO3 medium. The preparation of highly acid tolerant and efficient functional materials is a challenging task in the solid
phase recovery of noble metals. We have explored covalently functionalized graphene oxide (GO) to overcome this issue. GO was covalently functionalized with 1-(3-aminopropyl)imidazole (ImGO) (Ndonor)
and 2-methylthiophene (ThpGO) (S-donor) through amide or amine formation at different reactive sites. The prepared materials before and after Pd recovery were thoroughly characterized using a variety of state-of-the-art techniques. Solid-phase extraction experiments revealed that the Pd was recovered with remarkable selectivity from HLLW-like solutions in 3 M HNO3 using both the functionalized materials. The extraction efficiency was found to be higher than that of any of the solidstate materials reported to date. The sorption of Pd onto ImGO and ThpGO was best expressed by the Freundlich isotherm model. The advantages of the prepared materials are twofold: the first one is the
high tolerance to harsh acidic conditions, and the second one is the higher selectivity and efficiency for Pd. The sorption of Pd onto ImGO was achieved by complete anion exchange with the nitrate ion,
whereas ThpGO recovered Pd through a co-ordination mechanism. The results demonstrated that the developed covalently functionalized GO was the first choice material for the efficient and selective recovery of Pd..
98. Chitiphon Chuaicham, Radhesham Pawar, Keiko Sasaki, Dye-sensitized Photocatalyst of Sepiolite for Organic Dye Degradation, Catalysts, 9(2019) 235-251, 2018.12.
99. Subbaiah Muthu Prabhu, Shunsuke Imamura, Keiko Sasaki*, Mono-, di- and tri-carboxylic acid facilitated lanthanum-based organic frameworks: Insights into the structural stability and mechanistic approach for superior adsorption of arsenate from water, ACS Sustainable Chemistry and Engineering, in press, 2018.12, In this study, we synthesized three metal organic frameworks (MOFs) of La, with benzoic acid (BA), 1,4-benzene dicarboxylic acid (BDC) and 1,3,5-benzenetricarboxylic acid (BTC), abbreviated as La-BA, La-BDC and La-BTC, respectively. Interestingly, the BA ligand approached La metal to form lanthanum methanoate (La(HCOO)3 instead of the La-BA MOF through an acid catalyst amide-hydrolysis mechanism, whereas La-BDC and La-BTC act as MOFs, confirmed by PXRD patterns. The mechanism of MOF formation was revealed through PXRD, FT-IR, XPS and ICP-OES analyses. This is the first report to investigate AsO43- adsorption and the dissolution behavior of La-BA, La-BDC and La-BTC in detail using different spectroscopic methods. The maximum adsorption capacities of AsO43- obtained from the Langmuir isotherm model were found to be 2.623, 3.891 and 0.280 mmol/g for La-BA, La-BDC and La-BTC, respectively, where the the dose ratio of 1 g/L with the speed of 100 rpm at room temperature. The value for La-BDC was significantly superior to the previously reported adsorbents for AsO43- to date. The presence of AsO43- on both La-BA and La-BDC was confirmed by FTIR and XPS As 3d. The PXRD patterns confirmed the formation of LaAsO4 by the precipitation mechanism after adsorption of 2.4 mM AsO43- on both La-BA and La-BDC. Sorption kinetic data of AsO43- followed a pseudo-second-order model, which is consistent with chemisorption involving the possible coordination of AsO43- on La-BA and La-BDC. These results suggested that the MOF materials can be developed for the immobilization of AsO43- from waste water..
100. Santisak Kitjanukit; Keiko Sasaki; Naoko Okibe, Production of highly-catalytic, archaeal Pd(0) bionanoparticles using Sulfolobus tokodaii, Extremophile, in press., 2018.12.
101. Paulmanickam Koilraj, Yuta Kamura, Keiko Sasaki, Cosorption Characteristics of SeO4 2- and Sr2+ Radioactive Surrogates Using 2D/2D Graphene Oxide-Layered Double Hydroxide Nanocomposites, ACS Sustainable Chemistry and Engineering, 10.1021/acssuschemeng.8b02056, 6, 11, 13854-13866, 2018.11, Cosorption of anionic and cationic radioactive nuclides is highly desired toward the total cleaning of radioactive contaminated wastewater. A 2D/2D multifunctional nanocomposite of MgAl-LDH/graphene oxide (GO) was fabricated using coagulation and applied for the cosorption of Sr2+ and SeO4 2- from aqueous solution. The cosorption was synergetically enhanced with the copresence of each species and showed a maximum Sr2+ removal of 2.435 mmol/g of GO. The synergetic effect occurs only in the MgAl-LDH/GO nanocomposite because of the synchronized effect of MgAl-LDH, GO, and alkaline cations, which were not present in pure GO. The SeO4 2- removal occurred by the interchange of the NO3 - anion from the LDH, while the removal of Sr2+ occurred through coordination with carboxyl/alkoxy (âCOO-/-CO-) groups in GO by the ring opening of epoxides. The cosorption efficiencies of Sr2+ and SeO4 2- were stable in the wide pH range of 4-10. The binary (Na2SeO4 + SrCl2) and ternary (Na2SeO4 + SrCl2 + M+/M2+ = other metal ions or An- = other negative ions) systems enhanced the cosorption of Sr2+ and SeO4 2- in the presence of other alkali and alkali earth metals and other anions compared with the single system. The Sr2+ and SeO4 2- sorption densities were superior to previously reported values. The combined multifunctional ability and environmentally benign nature of the MgAl-LDH/GO composite is promising as a sustainable material for the total remediation of Sr2+ and SeO4 2- radioactive surrogates and can also be extended to wide combinations of divalent anions and cations..
102. Quanzhi Tian, Binglin Guo, Shingo Nakama, Keiko Sasaki, Distributions and Leaching Behaviors of Toxic Elements in Fly Ash, ACS Omega, 10.1021/acsomega.8b02096, 3, 10, 13055-13064, 2018.10, Fly ash usually contains a considerable amount of toxic elements that can be leached into the environment, thereby easily leading to serious contaminations. In this work, the leaching behaviors of poisonous elements including boron (B), phosphorus (P), vanadium (V), chromium (Cr), arsenic (As), selenium (Se), molybdenum (Mo), antimony (Sb), and tungsten (W) from fly ash were explored by sequential extraction. Importantly, the associations of these elements in fly ash were discussed based on their leaching and X-ray absorption near-edge structure (XANES) results. From the XANES results, it was observed that V(IV), Cr(III), As(V), Se(IV), and W(IV) were their main states of existence in fly ash. In terms of leaching results, large amounts of Mo and W were leached into pure water, which indicated their high mobilities. Furthermore, the occurrence of Mo in fly ash was mainly in the form of oxides, and W had complex associations including WX
4
(X can be monovalent anions), its reduction state or association with the elements that can be oxidized, and existence in silicates. B was as easily released into the environment as Mo and W. It can have several associations with the other cations, such as Ca
2+
, Na
+
, and Mg
2+
, and occurs in silicates. In contrast, most of the Cr and Sb were locked in silicates, indicating that they were very stable in fly ash. In addition, P, V, and As can exist within the structure of silicates as well. However, a considerable amount of them leached in the reduction step with a low pH. Hence, they can be associated with Ca
2+
, Na
+
, Mg
2+
, or Fe
3+
. In terms of Se, oxidation processes played an important role in controlling its leaching because of the oxidation of Se(IV) to Se(VI). Calcium selenite should be the predominant form of Se in fly ash..
103. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Masashi Yamane, Eri Takida, Shigeto Kuroiwa, Yuji Imaizumi, Effect of Fenton-like oxidation reagent on hydrophobicity and floatability of chalcopyrite and molybdenite, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2018.06.029, 554, 34-48, 2018.10, A fundamental study is provided in this work to understand the effect of Fenton-like reagent made by the addition of FeSO4 in H2O2 aqueous solution on surface hydrophobicity and floatability of chalcopyrite (CuFeS2) and molybdenite (MoS2). Contact angle measurements were performed to assess the surface hydrophobicity. The contact angle results showed that Fenton-like reagent could alter the surface hydrophobicity of chalcopyrite at lower concentration of H2O2 aqueous solution compared to that of using H2O2 aqueous solution. On the other hand, molybdenite surface remained hydrophobic after the oxidation treatments using Fenton-like reagent and H2O2 aqueous solution. Surface characterizations using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) shows that the chalcopyrite surface covered with a thicker layer of oxidation products after the oxidation treatment using Fenton-like reagent, indicating a stronger surface oxidation. Flotation results were in agreement with contact angle results, showing that Fenton-like reagent could depress the floatability of chalcopyrite at lower concentration of H2O2 aqueous solution. On the other hand, molybdenite recovery remained high under various oxidation treatments owing to low surface oxidation..
104. Kancharla Srinivasarao, Subbaiah Muthu Prabhu, Wuhui Luo, Keiko Sasaki, Enhanced adsorption of perchlorate by gemini surfactant-modified montmorillonite
Synthesis, characterization and their adsorption mechanism, Applied Clay Science, 10.1016/j.clay.2018.07.010, 163, 46-55, 2018.10, Organo-montmorillonites (OMt) adsorb perchlorate (ClO4 ) through anion exchange mechanism. Each gemini surfactant (GCn) provides two anion exchangeable sites due to its unique molecular structure. Due to the presence of more anion exchangeable sites, the preparation of OMt with GCn enables the possibility for higher amount of ClO4 uptake than their single-chain counterparts. In this work, gemini surfactant modified montmorillonites (GCn-Mt) were synthesized using three different alkyl chain length containing gemini surfactants (CnH2n+1(Me)2-C6H12-CnH2n+1(Me)2·2Cl), where n varied to 12, 14 and 16 and were examined in detail for the adsorption of ClO4 from aqueous solution. The structure of the GCn-Mt before and after adsorption of ClO4 was characterized by an array of techniques such as powder XRD, FT-IR, XPS, TGA and CHN analysis. The adsorption of ClO4 onto the GCn-Mt was best described by the Langmuir adsorption isotherm and pseudo-second-order kinetic model. The GC16-Mt showed the highest removal capacity of 1.08 mmol/g and at a rapid rate, achieving 95% within 1 min, with an equilibrium time of 15 mins. The GC16-Mt retained its high removal capacity and selectivity in presence of a variety of coexisting anions such as HCO3 , NO3 , CO3 2−, SO4 2−, SiO3 2−, and H2PO4 , and at a wide pH range (2−12). Combining the high removal capacity and selectivity with fast kinetics, the GCn-Mt has great potential for ClO4 removal from aqueous solutions..
105. Paulmanickam Koilraj, Yuta Kamura, Keiko Sasaki, Co-immobilization characteristics of SeO42- and Sr2+ radioactive surrogates using 2D/2D graphene oxide-layered double hydroxide nanocomposites, ACS Sustainable Chemistry in Engineering, 2018.09.
106. Subbaiah Muthu Prabhu, Kancharla Srinivasarao, Keiko Sasaki, Synthesis of modulator-driven highly stable zirconium-fumarate frameworks and their mechanistic investigations for the adsorption of arsenite and arsenate from aqueous solutions, RSC Cryst Eng Comm, in press, 2018.09.
107. Quanzhi Tian, Binglin Guo, Shingo Nakama, Keiko Sasaki, Distributions and Leaching Behaviors of Toxic Elements in Fly Ash, ACS Omega, 2018.09.
108. Binglin Guo, Shingo Nakama, Quanzhi Tian, Niko Dian Pahlevi, Li Zhang, Zhaochu Hu, Keiko Sasaki, Suppression mechanisms of anionic pollutants released from fly ash by different Ca additives, J. Hazard. Mater., 371(2019)474-483, 2018.09.
109. Masahito Tanaka, Keiko Sasaki, Naoko Okibe, Behavior of sulfate ions during biogenic scorodite crystallization from dilute As(III)-bearing acidic waters, Hydrometallurgy, 10.1016/j.hydromet.2018.07.018, 180, 144-152, 2018.09, This study revealed the importance of SO4
2− ions during biogenic scorodite crystallization via a two-stage As-removal process, using a combination of liquid and solid analyses (chemical digestion, FT-IR, SEM, TG-DTA, particle distribution). The first-stage As-removal was induced by microbial oxidation of Fe2+ and As(III), precipitating SO4
2−-bearing amorphous precursors composed of basic ferric sulfate (MFex(SO4)y(OH)z) and ferric arsenate (FeAsO4·(2 + n)H2O). This was followed by an induction period (a period of constant concentration), where dissolution-recrystallization of unstable amorphous precursors proceeded: Re-dissolved metal ions became locally concentrated on the surface of precursors, which gave the driving force for the second-stage As-removal as secondary layers of crystalline biogenic scorodite (Fe(AsO4)0.94(SO4)0.08·1.69H2O) out of even more dilute and seeded solution. This phase transformation process was also accompanied by continuous dehydration. This two-stage As-removal via SO4
2−-mediated phase transformation was shown to be key to promote biogenic scorodite formation with greater final As-removal from dilute As(III)-bearing solutions..
110. Keiko Sasaki, Yoshikazu Hayashi, Kenta Toshiyuki, Binglin Guo, Simultaneous immobilization of borate, arsenate, and silicate from geothermal water derived from mining activity by co-precipitation with hydroxyapatite, Chemosphere, 10.1016/j.chemosphere.2018.05.074, 207, 139-146, 2018.09, The treatment of the geothermal water discharged through mining activity is a critical issue because the rate of discharge is 12,000 m3 per day and the discharge contains high concentrations of borate (>20 mg/L) and arsenate (ca. 0.4 mg/L) as well as silicate and carbonate. The simultaneous reduction of borate and arsenate concentrations to acceptable levels was successfully performed by co-precipitation with hydroxyapatite (HAp). Although the coexisting high concentrations of carbonate act as a disturbing element, the co-precipitation equilibrium of borate was shifted to lower values by adjusting the P/Ca molar ratio, and the removal rate of borate was accelerated by using Al3+ additives, resulting in the efficient reduction of borate within 1 h. The initially immobilized boron in HAp is in the tetragonal form, which probably occupies the hydroxyl sites in HAp, gradually transforming into the trigonal form in the solid state, as interpreted by 1H NMR and 11B-NMR. The coexisting silicate was also immobilized in an ellestadite form, as confirmed by 29Si-NMR measurements. Arsenate and silicate were immobilized before borate in geothermal water. A dissolution assay of borate in the solid residues after co-precipitation with HAp verified the acceptable stability of borate, which is independent of the amount of added Al3+..
111. Kancharla Srinivasarao, Subbaiah Muthu Prabhu, Wuhui Luo, Keiko Sasaki, Enhanced adsorption of perchlorate by gemini surfactant-modified montmorillonite: Synthesis, characterization and their adsorption mechanism, Applied Clay Science, org/10.1016/j.clay.2018.07.010, 163, 46-55, 2018.07.
112. Keiko Sasaki, Yoshikazu Hayashi, Kenta Toshiyuki, Binglin Guo, Simultaneous immobilization of borate, arsenate, and silicate from geothermal water derived from mining activity by co-precipitation with hydroxyapatite, Chemosphere, 207, 139-146, 2018.06, The treatment of the geothermal water discharged through mining activity is a critical issue because the rate of discharge is 12,000m3 per day and the discharge contains high concentrations of borate (>20 mg/ L) and arsenate (ca. 0.4 mg/L) as well as silicate and carbonate. The simultaneous reduction of borate and arsenate concentrations to acceptable levels was successfully performed by co-precipitation with hydroxyapatite element, the co-precipitation equilibrium of borate was shifted to lower values by adjusting the P/Ca molar ratio, and the removal rate of borate was accelerated by using Al3þ additives, resulting in the efficient reduction of borate within 1 h. The initially immobilized boron in HAp is in the tetragonal form, which probably occupies the hydroxyl sites in HAp, gradually transforming into the trigonal form in the solid state, as interpreted by 1H NMR and 11B-NMR. The coexisting silicate was also immobilized in an
ellestadite form, as confirmed by 29Si-NMR measurements. Arsenate and silicate were immobilized before borate in geothermal water. A dissolution assay of borate in the solid residues after coprecipitation with HAp verified the acceptable stability of borate, which is independent of the amount of added Al3+..
113. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Effect of Fenton-like oxidation reagent on hydrophobicity and floatability of chalcopyrite and molybdenite, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 554, 34-48, 2018.06.
114. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Masashi Yamane, Eri Takida, Shigeto Kuroiwa, Yuji Imaizumi, Selective flotation of chalcopyrite and molybdenite using H2O2 oxidation method with the addition of ferrous sulfate, Minerals Engineering, 10.1016/j.mineng.2018.02.005, 122, 312-326, 2018.06, Hydrogen peroxide (H2O2) has been used as an oxidizing agent in the selective flotation of chalcopyrite and molybdenite. However, this method required relatively high concentration of H2O2 to deliver flotation results (i.e., mineral grades and recoveries) comparable to those obtained by the conventional copper-molybdenum (Cu-Mo) ores flotation using sodium hydrosulfide (NaHS). Therefore, further improvements are needed to reduce the consumption of H2O2 reagent. In this study, ferrous sulfate (FeSO4) was used to enhance the oxidation performance of H2O2 through Fenton-like reactions. Flotation results showed that the consumption of H2O2 reagent could be reduced by the addition of FeSO4 without losing the flotation selectivity. The reason might be caused by increasing of oxidation performance as indicated by the increasing concentration of dissolved oxygen after the addition of FeSO4 into the H2O2 aqueous solution. Surface analysis using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) images showed that the surface of chalcopyrite was covered by more hydrophilic precipitates after the oxidation treatment using H2O2 aqueous solution with the addition of FeSO4, thus more hydrophilic surface and lower floatability. On the other hand, the surface of molybdenite was slightly oxidized and its surface remained hydrophobic as confirmed from contact angle results. Flotation tests using Cu-Mo bulk concentrate demonstrated that selective flotation might be possible using a mixture of FeSO4 and H2O2 aqueous solution. Moreover, this new method could be used as an alternative to copper depressant in Cu-Mo selective flotation, replacing the NaHS reagent..
115. Paulmanickam Koilraj, Yuta Kamura, Keiko Sasaki, Synergetic co-immobilization of SeO42- and Sr2+ from aqueous solution onto graphene oxide and carbon-dot based layered double hydroxide nanocomposites and their mechanistic investigation, RSC J. Material Chemistry A, 10.1039/C8TA01605D, 6, 10008-10018, 2018.05, The co-immobilization of radioactive Sr2+ and SeO42- using a multifunctional material is an interesting area of research for the total remediation of radioactive wastes. However, it is rather challenging to target both the anion and cation through the realization of a multifunctional ability of the resultant sorbent. In this work, MgAl–NO3-layered double hydroxides (LDHs) containing graphene oxide (GO) and carbon dot (C-dot) nanocomposites were synthesized and contrasted for the co-immobilization of Sr2+ and SeO42-. Zeta potential measurements and TEM observation of the MgAl–NO3-LDH/C-dot composite indicated that the carbon-nanodot was attached to the surface of LDH nanosheets, while in the MgAl–NO3-LDH/GO composites the LDH nanosheets were decorated on the larger sized GO nanosheets. Adsorption studies found that the normalized Sr2+ adsorption capacity was 1.793 mmol g-1 on MgAl–NO3-LDH/GO, which was nine times higher than that for the MgAl–NO3-LDH/C-dot composite and GO. The enhancement in the Sr2+ adsorption capacity is due to the co-operative effect of the LDH and GO. The adsorption of Sr2+ on the MgAl–NO3-LDH/C-dot occurs by coordination with the –COO group, while ligand exchange and ionic interaction with the alkoxide anion are the dominant mechanisms on the MgAl–NO3-LDH/GO composite. Moreover, the adsorption capacity of both Sr2+ and SeO42- increased synergistically in the bi-component system containing both ions. The present technique is promising and offers a sustainable and environmentally friendly multifunctional material for the co-immobilization of both anionic and cationic radioactive surrogates from aqueous solutions..
116. Hajime Miki, Tsuyoshi Hirajima, Yukihiro Muta, Gde Pandhe Wisnu Suyantara, Keiko Sasaki, Effect of sodium sulfite on floatability of chalcopyrite and molybdenite, Minerals, 10.3390/min8040172, 2018.05.
117. Zhisheng Gao, Keiko Sasaki, Xinhong Qiu, Structural memory effect of Mg-Al and Zn-Al layered doubled hydroxides in the presence of natural humic acid, Langmuir, 10.1021/acs.langmuir.8b00059, 34, 5386-5395, 2018.05, The structural memory effect of layered double hydroxides (LDHs) is one of the important reasons for their extensive use in environmental remediation. In this study, humic acid (HA) was extracted from black soil and sediments and characterized to determine their structures. The regeneration mechanisms of calcinated LDHs (CLDHs) including different divalent metals (Mg-CLDH and Zn-CLDH) in deionized water and different HA solutions were carefully elucidated, and the reasons for the behavior differences in the two materials were explained. The presence of the HAs significantly increased the dissolution rate of Mg2+ ions from Mg-CLDHs and subsequent regeneration of Mg-LDH. Because of the diverse functional groups in the HAs, these groupswere complexed with metallic ions such as Mg2+ on the surface of Mg- CLDH in the beginning. During the process, the HAs adsorbed the regenerated LDHs on the surfaces. Therefore, the crystallinity, morphology, and specific surface area of the regenerated Mg-LDH significantly changed, especially in the presence of high concentrations of HA. In the case of Zn-CLDH, the regeneration rate of the LDH increased in the presence of HA, but the surface of Zn-CLDH was covered with regenerated Zn-LDH and HA. Then, the inside of the particles could not transform to LDH, leading to poor crystallinity and a significant increase in the ZnO content of the HA system..
118. Subbaiah Muthu Prabhu, Chitiphon Chuaicham, Keiko Sasaki, A Mechanistic Approach for the Synthesis of Carboxylate-Rich Carbonaceous Biomass-Doped Lanthanum-Oxalate Nanocomplex for Arsenate Adsorption, ACS Sustainable Chemistry and Engineering, 10.1021/acssuschemeng.7b04678, 6, 5, 6052-6063, 2018.05, Considering the protocol of "zero-alkaline waste disposal" for green and arsenic-free environment, lanthanum (La3+)-based MOF-like complex materials were designed, and the complex materials have been employed as adsorbent for AsO4
3- adsorption from water. The sucrose-derived porous carbon (SPC)@La-oxalate complex was prepared by a simple one-pot coprecipitation method at room temperature, where oxalate has been used as an organic ligand, and the carbonaceous biomass has been used as a doping material that is naturally a carboxylate-rich functional group derived from a sucrose biomass. In addition to SPC@La-oxalate, bare-SPC, La(OH)3, and SPC@La(OH)3 were also prepared via simple base-addition conventional methods, and their performances in AsO4
3- removal were compared. The FTIR peak at 848 cm-1 confirmed the presence of AsO4
3- on the SPC@La-oxalate complex after adsorption of 1 mM AsO4
3-. The high resolution X-ray photoelectron spectrum for the AsO4
3- adsorbed SPC@La-oxalate showed a peak at EB[As 3d] = 45.2 eV, which could be attributed to As5+. The EXAFS of the As K-edge revealed that there are two distinct atomic shells, As-O with the distance of 1.68 Å and As-La with the distance of 3.32 Å, indicating the formation of monodentate complex of La with AsO4
3-. Additionally, an electrostatic interaction and hydrogen bonding are also possible adsorption mechanism in acidic conditions. The SPC@La-oxalate complex adsorbent showed excellent dearsenate behavior of 1.093 mmol/g, and the maximum AsO4
3- removal was maintained in a wide pH range from 3 to 8. Sorption kinetic data were the best expressed by a pseudo-second-order rate equation, and the maximum adsorption capacity was 1.858 mmol/g based on Langmuir monolayer adsorption. Compared with previous reports, SPC@La-oxalate adsorbent could be easily prepared, and the uptake amounts for AsO4
3- were enriched. Reusability of the material after six cycles is yet another advantage to the present adsorbent. This work will help to facilitate the research on novel complex adsorbents for the removal of AsO4
3- from water..
119. Niko Dian Pahlevi, Binglin Guo, Keiko Sasaki, Immobilization of selenate in cancrinite using a hydrothermal method, Ceramics International, 10.1016/j.ceramint.2018.02.083, 44, 7, 8635-8642, 2018.05, Because of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, radioactive species were leaked out, including selenium isotopes (79Se). Developing a stable matrix that is suitable for longterm storage is necessary for the decommissioning process of the FDNPP. In the present work, the co-precipitation of SeO4 2− in cancrinite/sodalite as a potential stable matrix was investigated at various reaction times using a hydrothermal method. Over time, the SeO4 2− contents in the solid products gradually increased. The XRD patterns revealed that the reaction produced multi-phased precipitates, which were zeolite Na (P), sodalite, and cancrinite. As the SeO4 2− amount increased, the solid products were transformed to cancrinite. The calculated lattice parameter of sodalite and cancrinite showed an increase in lattice parameter a for sodalite and cancrinite, suggesting SeO4 2− incorporated into the sodalite/cancrinite structure. XRD, SEM, FTIR, 27Al-NMR, and 29Si-NMR results revealed the phase transformation of the solid products over time. Four stages of the co-precipitation mechanism are proposed, including the formation of zeolite P (Na), hydroxylation of zeolite P (Na), the formation of sodalite, and cancrinite reprecipitation..
120. Yusei Masaki, Tsuyoshi Hirajima, Keiko Sasaki, Hajime Miki, Naoko Okibe, Microbiological Redox Potential Control to Improve the Efficiency of Chalcopyrite Bioleaching , Geomicrobiol. J., 10.1080/01490451.2018.1443170, 2018.03.
121. Subbaiah Muthu Prabhu, Chitiphon Chuaicham, Keiko Sasaki, A Mechanistic Approach for the Synthesis of Carboxylate-Rich Carbonaceous Biomass-Doped Lanthanum-Oxalate Nanocomplex for Arsenate Adsorption, ACS Sustainable Chemistry & Engineering, doi/10.1021/acssuschemeng.7b04678, 6, 6052-6063, 2018.03.
122. Masahito Tanaka, Naoko Okibe, Keiko Sasaki, Factors to Enable Crystallization of Environmentally Stable Bioscorodite from Dilute As(III)-Contaminated Waters., Minerals, 2018, 8, 23., 10.3390/min8010023, 2018.03.
123. Wuhui Luo, Keiko Sasaki, Tsuyoshi Hirajima, Influence of the pre-dispersion of montmorillonite on organic modification and the adsorption of perchlorate and methyl red anions, Applied Clay Science, 10.1016/j.clay.2017.12.032, 154, 1-9, 2018.03.
124. Keiko Sasaki, Kenta Toshiyuki, Binglin Guo, Keiko Ideta, Yoshikazu Hayashi, Tsuyoshi Hirajima, Jin Miyawaki, Calcination effect of borate-bearing hydroxyapatite on the mobility of borate, Journal of Hazardous Materials, 10.1016/j.jhazmat.2017.10.003, 344, 90-97, 2018.02.
125. Niko Dian Pahlevi, Binglin Guo, Keiko Sasaki, Immobilization mechanism of selenate in cancrinite by hydrothermal method, Ceramic International, 2018.01.
126. Gde Pandhe Wisnu SUYANTARA, Tsuyoshi HIRAJIMA, Hajime MIKI, Keiko SASAKI, Floatability of molybdenite and chalcopyrite in artificial seawater, Minerals Engineering, 10.1016/j.mineng.2017.10.004, 115, 117-130, 2018.01.
127. Subbaiah Muthu Prabhu, Shunsuke Imamura, Keiko Sasaki, Mono-, di- and tri-carboxylic acid mediated lanthanum based organic frameworks: Insights into the mechanistic approach for superior adsorption of arsenate from water, ACS Sustainable Chemistry in Engineering, 2018.01.
128. Paulmanickam Koilraj, Yuta Kamura, Keiko Sasaki, Synergetic co-immobilization of SeO42- and Sr2+ from aqueous solution onto multifunctional graphene oxide and carbon-dot based layered double hydroxide nanocomposites and their mechanistic investigation, Journal of Materials Chemistry A, 10.1039/c8ta01605d, 6, 21, 10008-10018, 2018.01, The co-immobilization of radioactive Sr2+ and SeO42- using a multifunctional material is an interesting area of research for the total remediation of radioactive wastes. However, it is rather challenging to target both the anion and cation through the realization of a multifunctional ability of the resultant sorbent. In this work, MgAl-NO3-layered double hydroxides (LDHs) containing graphene oxide (GO) and carbon-dot (C-dot) nanocomposites were synthesized and contrasted for the co-immobilization of Sr2+ and SeO42-. Zeta potential measurements and TEM observation of the MgAl-NO3-LDH/C-dot composite indicated that the carbon-nanodot was attached to the surface of LDH nanosheets, while in the MgAl-NO3-LDH/GO composites the LDH nanosheets were decorated on the larger sized GO nanosheets. Adsorption studies found that the normalized Sr2+ adsorption capacity was 1.793 mmol g-1 on MgAl-NO3-LDH/GO, which was nine times higher than that for the MgAl-NO3-LDH/C-dot composite and GO. The enhancement in the Sr2+ adsorption capacity is due to the co-operative effect of the LDH and GO. The adsorption of Sr2+ on the MgAl-NO3-LDH/C-dot occurs by co-ordination with the -COO- group, while ligand exchange and ionic interaction with the alkoxide anion are the dominant mechanisms on the MgAl-NO3-LDH/GO composite. Moreover, the adsorption capacity of both Sr2+ and SeO42- increased synergistically in the bi-component system containing both ions. The present technique is promising and offers a sustainable and environmentally friendly multifunctional material for the co-immobilization of both anionic and cationic radioactive surrogates from aqueous solutions..
129. Paulmanickam Koilraj and Keiko Sasaki, Eco-Friendly Alkali-Free Arginine-Assisted Hydrothermal Synthesis of Different Layered Double Hydroxides and Their Chromate Adsorption/Reduction Efficiency, Chemistry Select, 10.1002/slct.201702134, Vol. 2, Issue 32, 10459-10469, 2017.11.
130. Binglin Guo, Keiko Sasaki, Tsuyoshi Hirajima, Solidification of ettringite after uptaking selenate as a surrogate of radionuclide in glass-ceramics by using industrial by-products, Journal of Materials Science, 10.1007/s10853-017-1422-x, 52, 22, 12999-13011, 2017.11.
131. Paulmanickam Koilraj, Yuta Kamura, Keiko Sasaki, Carbon-Dot-Decorated Layered Double Hydroxide Nanocomposites as a Multifunctional Environmental Material for Co-immobilization of SeO4 2- and Sr2+ from Aqueous Solutions, ACS Sustainable Chemistry and Engineering, 10.1021/acssuschemeng.7b01979, 5, 10, 9053-9064, 2017.10.
132. Qianqian Yu, Toshihiko Ohnuki, Naofumi Kozai, Fuminori Sakamoto, Kazuya Tanaka, Keiko Sasaki, Quantitative analysis of radiocesium retention onto birnessite and todorokite, Chemical Geology, 10.1016/j.chemgeo.2017.09.008, 470, 141-151, 2017.10.
133. Binglin Guo, Keiko Sasaki, Tsuyoshi Hirajima, Selenite and selenate uptaken in ettringite
Immobilization mechanisms, coordination chemistry, and insights from structure, Cement and Concrete Research, 10.1016/j.cemconres.2017.07.004, 100, 166-175, 2017.10.
134. Binglin Guo, Keiko Sasaki, Tsuyoshi Hirajima, Characterization of the intermediate in formation of selenate-substituted ettringite, Cement and Concrete Research, 10.1016/j.cemconres.2017.05.002, 99, 30-37, 2017.09.
135. Wuhui Luo, Takeru Fukumori, Binglin Guo, Kwadwo Osseo-Asare, Tsuyoshi Hirajima, Keiko Sasaki, Effects of grinding montmorillonite and illite on their modification by dioctadecyl dimethyl ammonium chloride and adsorption of perchlorate, Applied Clay Science, https://doi.org/10.1016/j.clay.2017.06.025, Vol.146, 15, 325-333, 2017.09.
136. Wuhui Luo, Sasaki Keiko, Tsuyoshi Hirajima, Necessity of pre-dispersion of montmorillonite for its organic modification and the influence on adsorption of perchlorate and methyl red by modified composites, Applied Clay Science, 2017.08.
137. Binglin Guo, Sasaki Keiko, Tsuyoshi Hirajima, Selenite and selenate uptaken in ettringite: Immobilization mechanisms, coordination chemistry and insights from structure, Concrete and Cement Research, 2017.07.
138. Bigling Guo, Sasaki Keiko, Tsuyoshi Hirajima, Structural transformation of selenate ettringite: a hint for exfoliation chemistry, RSCAdvances, 10.1039/c7ra08765a, 7, 42407-42415, 2017.06.
139. Paulmanickam Koilraj, Keiko Sasaki, Selective removal of phosphate using La-porous carbon composites from aqueous solutions
Batch and column studies, Chemical Engineering Journal, 10.1016/j.cej.2017.02.075, 317, 1059-1068, 2017.06.
140. Binglin Guo, Sasaki Keiko, Tsuyoshi Hirajima, Characterization of an intermediate in formation of selenate-substituted ettringite, Cement and Concrete Research, http://dx.doi.org/10.1016/j.cemconres.2017.05.002, 99, 30-37, 2017.05.
141. Binglin Guo, Sasaki Keiko, Tsuyoshi Hirajima, Solidification of ettringite after uptaking selenate as a surrogate of radionuclide in glass-ceramics by using industrial byproducts, Journal of Material Sciences, in press, 2017.05.
142. Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki, Experimental study on freeze drying of Loy Yang lignite and inhibiting water re-adsorption of dried lignite, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2017.01.076, Vol.520, 146-153, 2017.05.
143. Subbaiah Muthu Prabhu, Paulmanickam Koilraj, Sasaki Keiko, Synthesis of sucrose-derived amorphous carbon-doped ZrxLa1-xOOH materials and their superior performance for the simultaneous depollution of arsenite and fluoride from binary systems, Chemical Engineering Journal, doi.org/10.1016/j.cej.2017.05.052, 325, 1-13, 2017.04.
144. Paulmanickam Koilraj, Sasaki Keiko, Biomolecule-assisted interlayer anion-controlled layered double hydroxide as an efficient sorbent for arsenate removal, Journal of Materials Chemistry A, in press, 2017.04.
145. Wuhui Luo, Tsuyoshi Hirajima, Keiko Sasaki, Selective adsorption of inorganic anions on unwashed and washed hexadecyl pyridinium-modified montmorillonite, Separation and Purification Technology, 10.1016/j.seppur.2016.12.004, 176, 120-125, 2017.04.
146. Kojo T. Konadu, Keiko Sasaki, Takashi Kaneta, Grace Ofori-Sarpong, Kwadwo Osseo-Asare, Bio-modification of carbonaceous matter in gold ores
Model experiments using powdered activated carbon and cell-free spent medium of Phanerochaete chrysosporium, Hydrometallurgy, 10.1016/j.hydromet.2016.08.003, 168, 76-83, 2017.03.
147. Naoko Okibe, Shiori Morishita, Masahito Tanaka, Keiko Sasaki, Tsuyoshi Hirajima, Kazuhiro Hatano, Atsuko Ohata, Bioscorodite crystallization using Acidianus brierleyi
Effects caused by Cu(II) present in As(III)-bearing copper refinery wastewaters, Hydrometallurgy, 10.1016/j.hydromet.2016.07.003, 168, 121-126, 2017.03.
148. Paulmanickam Koilraj, Sasaki Keiko, Selective removal of phosphate using La-porous carbon composites from aqueous solutions: Batch and column studies, Chemical Engineering Journal, doi.org/10.1016/j.cej.2017.02.075, 317, 1059-1068, 2017.02.
149. Sasaki Keiko, Kenta Toshiyuki, Binglin Guo, Tsuyoshi Hirajima, Calcination effect of borate-bearing hydroxyapatite on mobility of borate, J Hazard Mater, 2017.02.
150. Subbaiah Muthu Prabhu, Sasaki Keiko, Fabrication of chitosan-reinforced ZrxAl1-xOOH nanocomposites and their arsenite and fluoride depollution densities from single/binary systems, Chemistry Select, in press., 2017.02.
151. Wuhui Luo, Akihiro Inoue, Tsuyoshi Hirajima, Keiko Sasaki, Synergistic effect of Sr2+ and ReO4 adsorption on hexadecyl pyridinium-modified montmorillonite, Applied Surface Science, 10.1016/j.apsusc.2016.10.135, 394, 431-439, 2017.02.
152. Kojo Twum-Knadu, Sasaki Keiko, Takashi Kaneta, Grace Ofori-Sarpong, Kwadwo Osseo-Asare, Bio-modification of carbonaceous matters in gold ore: Model experiments using powdery activated charcoal and cell-free extracts of Phanerochaete chrysosporium, Hydrometallurgy, 168 (2017) 76–83, 2017.01.
153. Wuhui Luo, Tsuyoshi Hirajima, Sasaki Keiko, Selective adsorption of inorganic anions on unwashed and washed hexadecyl pyridinium-modified montmorillonite, Separation and Purification Technology , 176, 120-125, 2017.01.
154. Wuhui Luo, Akihiro Inoue, Tsuyoshi Hirajima, Sasaki Keiko, Synergistic effect on binary adsorption system of Sr2+ and ReO4- as radionuclide surrogates by hexadecyl pyridinium-modified montmorillonite, Applied Surface Science, http://dx.doi.org/10.1016/j.apsusc.2016.10.135, 394, 431-439, 2017.01.
155. Sasaki Keiko, Shugo Nagato, Keiko Ideta, Jin Miyawaki, Tsuyoshi Hirajima, Enhancement of fluoride removal by co-precipitation with Al-substituted hydroxyapatite, Chem. Engng. J., doi.org/10.1016/j.cej.2016.11.096, 311, 284-292, 2017.01.
156. Tsuyoshi Hirajima, Hajime Miki, Gde Pandhe Wisnu Suyantara, Sasaki Keiko, Selective flotation of chalcopyrite and molybdenite with H2O2 oxidation, Minerals Engineering, 100, 83-92, 2017.01.
157. Dewi Agustina Iryani, Satoshi Kumagai, Moriyasu Nonaka, Keiko Sasaki, Tsuyoshi Hirajima, Characterization and Production of Solid Biofuel from Sugarcane Bagasse by Hydrothermal Carbonization, Waste and Biomass Valorization, 10.1007/s12649-017-9898-9, 8, 6, 1941-1951, 2017.01.
158. Subbaiah Muthu Prabhu, Keiko Sasaki, Fabrication of Chitosan-Reinforced ZrxAl1-xOOH Nanocomposites and Their Arsenite and Fluoride Depollution Densities from Single/Binary Systems, ChemistrySelect, 10.1002/slct.201701072, 2, 22, 6375-6387, 2017.01.
159. Paulmanickam Koilraj, Keiko Sasaki, Kannan Srinivasan, Novel biomolecule-assisted interlayer anion-controlled layered double hydroxide as an efficient sorbent for arsenate removal, Journal of Materials Chemistry A, 10.1039/c7ta03056h, 5, 28, 14783-14793, 2017.01.
160. Tsuyoshi Hirajima, Hajime Miki, Gde Pandhe Wisnu Suyantara, Hidekazu Matsuoka, Ahmed Mohamed Elmahdy, Keiko Sasaki, Yuji Imaizumi, Shigeto Kuroiwa, Selective flotation of chalcopyrite and molybdenite with H2O2 oxidation, Minerals Engineering, 10.1016/j.mineng.2016.10.007, 100, 83-92, 2017.01.
161. Hajime Miki, Hidekazu Matsuoka, Tsuyoshi Hirajima, Gde Pandhe Wisnu Suyantara, Keiko Sasaki, Electrolysis oxidation of chalcopyrite and molybdenite for selective flotation, Materials Transactions, 10.2320/matertrans.M-M2017807, 58, 5, 761-767, 2017.01, Electrolysis oxidation of chalcopyrite and molybdenite was investigated, via various electrochemical methods, with the aim of realizing selective flotation of these minerals. Result of potential polarization indicated that oxidation via electrolysis affected only the chalcopyrite surface, owing mainly to the difference in conductivity of these minerals. Also measurements of contact angle after electrolysis indicated that contact angle of chalcopyrite selectively decreased whereas that of molybdenite did not decrease drastically. XPS analyses after electrolysis indicated that chalcopyrite peak decreased whereas iron oxyhydroxide (goethite) and iron sulfate increased, it suggests that these oxidation products covered on the surface of chalcopyrite. On the other hand, molybdenite peak is similar after electrolysis except for molybdenum oxide/oxygen with molybdenite can be seen for oxygen peak. From these results and general knowledge that sulfide hydrophobicity and sulfate/oxyhydroxide hydrophilicity, it can be explained that with electrolysis oxidation, hydrophilic oxihydroxide and sulfate covered on the surface of hydrophobic chalcopyrite then chalcopyrite surface became hydrophilic. On the other hand, molybdenite surface keep hydrophobic since its difficulty of oxidation and it is difficult to stay molybdenum oxide on the surface due to its soluble property. These results revealed that chalcopyrite was selectively oxidized and, hence, selective flotation of chalcopyrite and molybdenite was possible. This electrolysis oxidation methods were compared with those governing other oxidation treatments..
162. Keiko Sasaki, Shugo Nagato, Keiko Ideta, Jin Miyawaki, Tsuyoshi Hirajima, Enhancement of fluoride immobilization in apatite by Al3+additives, Chemical Engineering Journal, 10.1016/j.cej.2016.11.096, 311, 284-292, 2017.01, Immobilization of fluoride (F) in apatite using Ca(OH)2as a mineralizer in the presence of phosphate is known to be accompanied by a stagnation period. This is caused by the formation of hydroxyapatite and/or fluoroapatite (HAp/FAp) on the surface of Ca(OH)2, which inhibits the dissolution of Ca(OH)2. Al3+additives effectively eliminated the delay period, leading to the rapid formation of apatites by suppressing the formation of CaCO3. Zeta potential measurements clearly showed that increasing the quantity of Al3+additives caused not only a decrease in the initial surface charge but also a decrease in the rate of the surface charge of the solid residues during the reaction, indicating that Al3+additives enhanced the formation of HAp/FAp. 27Al-nuclear magnetic resonance (NMR) studies of the solid residues indicated that the predominant coordination number of Al was always hexagonal ([6]Al) and that the fraction of [6]Al increased with an increase in the molar ratio of F/Al in the solid residues, suggesting that the stable AlF6
3−complex was easily incorporated into the apatites. In addition, transmission electron microscope- energy dispersive X-ray spectroscopy (TEM-EDX) revealed a uniform distribution of Al in the apatites, which suggests that in the initial stages of the reaction, free Al3+ions contribute to the formation of apatite crystal seeds independent of Ca(OH)2particles, resulting in the efficient growth of apatites containing F. This result is helpful for the treatment of F-bearing industrial wastewaters in practical applications by using an Al-bearing Ca source, such as ground-granulated blast-furnace slag..
163. Kojo T. Konadu, Keiko Sasaki, Kwadwo Osseo-Asare, Takashi Kaneta, Enzymatic pre-treatment of carbonaceous matter in preg-robbing gold ores
Effect of ferrous ion additives, 22nd International Biohydrometallurgy Symposium, 2017 22nd International Biohydrometallurgy Symposium, 10.4028/www.scientific.net/SSP.262.43, 43-47, 2017.01, The bio-treatment of double refractory gold ores (DRGO) to reduce preg-robbing needs to account for the heterogeneity of the ore so as to acquire a much more complete picture of the system. To this end, the effects of ferrous ion additives on the degradation of powdered activated carbon (PAC) by cell-free spent medium (CFSM) was studied. Au(CN)2- adsorption and Raman spectrometric results suggest that the ferrous salt could have possibly reacted with some biogenic hydrogen peroxide to aid in the degradation of PAC. The bio-treatment produced mixed solid residues containing some partially degraded aromatic compounds which were soluble in alkaline solutions. Ultimately, biodegradation of PAC using CFSM in the presence of 50 µM FeSO4.7H2 O for 7 days followed by washing with 3 mM NaOH reduced Au(CN)2- uptake by 80%..
164. Keishi Oyama, Tsuyoshi Hirajima, Keiko Sasaki, Hajime Miki, Naoko Okibe, Mechanism of silver-catalyzed bioleaching of enargite concentrate, 22nd International Biohydrometallurgy Symposium, 2017 22nd International Biohydrometallurgy Symposium, 10.4028/www.scientific.net/SSP.262.273, 273-276, 2017.01, Silver-catalyzed bioleaching of enargite concentrate with three bacteria (Acidimicrobium ferrooxidans ICP, Sulfobacillus sibiricus N1, Acidithiobacillus caldus KU) and one archaeon (Ferroplasma acidiphilum Y) was conducted in order to elucidate the catalytic mechanism of silver sulfide in enargite bioleaching. Whereas Cu recovery remained relatively low (43%) and Fe dissolved completely without silver sulfide, Cu recovery was greatly enhanced (96%) and Fe dissolution was suppressed (29%) in the presence of 0.04% silver sulfide. In the latter case, 52% of the solubilized As was re-immobilized, in contrast to only 14% As re-immobilization in the former. The silver-catalyzed bioleaching (at 0.04% silver sulfide) proceeded at low redox potentials within the optimal range, which likely promoted enargite dissolution via formation of intermediate Cu2 S. XAFS analysis revealed that As was mainly immobilized as As(V), which was in agreement with the EPMA results detecting ferric arsenate passivation on some enargite grains. Furthermore, formation of trisilver arsenic sulfide (Ag3 AsS4) was detected by XRD and EPMA, covering the surface of enargite particles. An intermediate layer, consisting of (Cu,Ag)3 AsS4, was also observed between the enargite grain and trisilver arsenic sulfide layer, implying that Cu in enargite may be gradually substituted by solubilized Ag. Kinetic study suggested that these secondary minerals do not rate-limit the enargite dissolution. The overall mechanism of silver-catalyzed bioleaching of enargite concentrate will be proposed..
165. Yuta Era, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe, Microbiological as(III) oxidation and immobilization as scorodite at moderate temperatures, 22nd International Biohydrometallurgy Symposium, 2017 22nd International Biohydrometallurgy Symposium, 10.4028/www.scientific.net/SSP.262.664, 664-667, 2017.01, The potential utility of mesophilic/moderately thermophilic acidophiles was investigated for immobilization of arsenic (As) as scorodite (FeAsO4·2H2O) at moderate temperatures (35–45˚C). Here, the acid-tolerant mesophile Thiomonas cuprina Hö5 and acidophilic moderately thermophile Acidimicrobium ferrooxidans ICP were selected as As(III)- and Fe(II)- oxidizers, respectively. Due to a difference in their optimal growth pHs, a 2-step reaction consisting of the 1st As(III) oxidation step followed by the Fe(II) oxidation + precipitation step was studied. In our previous study, the optimal [Fe(II)]ini/[As(III)]ini molar ratio for bioscorodite formation at 70˚C (at [As(III)]ini = 1000 ppm) was shown to be around 1.4. However, setting the same molar ratio at moderate temperatures (35-45˚C) resulted in formation of unstable amorphous ferric arsenate. Lowering the ratio to ≤ 1.0 led to precipitation of crystalline bioscorodite with > 90% As(III) removal at 45˚C..
166. Masahito Tanaka, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe, Optimization of bioscorodite crystallization for treatment of as(III)-bearing wastewaters, 22nd International Biohydrometallurgy Symposium, 2017 22nd International Biohydrometallurgy Symposium, 10.4028/www.scientific.net/SSP.262.555, 555-558, 2017.01, Arsenic (As) is a major impurity contaminating metal refinery wastewaters. To immobilize As ions, we have previously reported microbial scorodite (FeAsO4·2H2O) crystallization using the thermo-acidophilic iron-oxidizing archaeon, Acidianus brierleyi. In order to extend the applicable range of As(III)-bearing metal refinery wastewaters (especially for dilute As(III) concentrations of 250–1500 ppm), this study investigated the effect of several factors possibly affecting the bioscorodite crystallization efficiency; (i) [Fe(II)]ini/[As(III)]ini molar ratio at different target As(III) concentrations, (ii) initial pH, and (iii) seed scorodite with different morphologies. The [Fe(II)]ini/[As(III)]ini molar ratio strongly affected the bioscorodite crystallization efficiency at each target As(III) concentration. Whilst the [Fe(II)]ini/[As(III)]ini molar ratio of 1.4 was most effective at 500–1500 ppm As(III), the optimal molar ratios for treating more dilute concentrations (< 500 ppm) were shown to be relatively higher. However, further increasing the [Fe(II)]ini/[As(III)]ini molar ratio resulted in formation of unwanted potassium jarosite (KFe3(OH)6(SO4)2) together with scorodite. Lowering the initial pH from 1.5 to 1.2 resulted in earlier scorodite nucleation, but lower overall As immobilization. Feeding chemical- and bio-scorodite seed crystals differently affected the reaction speed and the stability of newly-precipitated bioscorodite. The TCLP test indicated that scorodite formed on bioscorodite seeds is more stable than that formed on chemically-synthesized scorodite seeds..
167. Sumire Kudo, Airi Harada, Hiroe Kubota, Keiko Sasaki, Takashi Kaneta, Simultaneous Determination of Manganese Peroxidase and Lignin Peroxidase by Capillary Electrophoresis Enzyme Assays, ACS Omega, 10.1021/acsomega.7b00998, 2, 10, 7329-7333, 2017.01, Here, we developed an enzyme assay of manganese peroxidase (MnP) by capillary electrophoresis using an in-capillary reaction and applied it to a simultaneous assay of MnP and lignin peroxidase (LiP). The enzyme activity of MnP was determined from the peak area corresponding to Mn(III)-malonate produced by the plug-plug reaction between MnP and Mn(II) in a separation capillary. A background electrolyte containing 250 mM malonate buffer (pH 4.5) and 5 mM cetyltrimethylammonium bromide was employed for the separation of Mn(III)-malonate from MnP at -10 kV after a plug-plug reaction for 5 min. Although the assay permitted the determination of purified MnP, we found that both LiP and MnP have similar activities against their substrates, that is, LiP catalyzed the oxidation reaction of Mn(II) as well as MnP, whereas MnP catalyzed the oxidation reaction of veratryl alcohol which was the substrate used in the LiP assay developed previously. Thus, we proposed a method to discriminate MnP from LiP based on the difference in the activities of these enzymes to each substrate. Amounts of MnP and LiP in a mixture were successfully evaluated by the proposed method..
168. Subbaiah Muthu Prabhu, Paulmanickam Koilraj, Keiko Sasaki, Synthesis of sucrose-derived porous carbon-doped ZrxLa1-xOOH materials and their superior performance for the simultaneous immobilization of arsenite and fluoride from binary systems, Chemical Engineering Journal, 10.1016/j.cej.2017.05.052, 325, 1-13, 2017.01, Amorphous forms of mixed lanthanum-zirconium oxyhydroxide (ZrxLa1-xOOH) composite materials, containing porous sucrose carbon as a dopant (PSC-ZrxLa1-xOOH), were successfully prepared via co-precipitation and characterized by BET surface area analysis, Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) Energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA). These synthesized materials were utilized for the simultaneous adsorption of AsO3 3− and F from a binary mixture solution in batch tests. The ZrxLa1-xOOH and PSC-ZrxLa1-xOOH composite materials showed both fast adsorption rates and high adsorption capacities towards AsO3 3− and F in aqueous solution. Most attractively, ZrxLa1-xOOH and PSC-ZrxLa1-xOOH showed better F adsorption capacity when the pH was lower than 7, better AsO3 3− removal when the pH was higher than 9 and were superior to previously reported metallic oxide-based sorbents. The mechanism can be interpreted based on the HSAB principle, where the bimetallic oxyhydroxides become “soft acids”, while La3+ and Zr4+ are categorized as “hard acids”. Moreover, the PSC-ZrxLa1-xOOH adsorbent demonstrated high selectivity for AsO3 3− in the co-existence of other ions in a triple component system. The fast adsorption kinetics and high capacity make the designed PSC-ZrxLa1-xOOH adsorbent a promising advanced material for the removal of AsO3 3− and F from water in practical applications..
169. Paulmanickam Koilraj, Yu Takaki, Keiko Sasaki, Adsorption characteristics of arsenate on colloidal nanosheets of layered double hydroxide, Applied Clay Science, 10.1016/j.clay.2016.06.002, 134, 110-119, 2016.12, Nanomaterials have gained much interest in water remediation and pollution control in recent years. However, the toxicity associated with nanoparticles remaining in solution after remediation has high impact on the environment. The present study examined the synthesis and characterization of colloidal Mg2Al-NO3 layered double hydroxide (Mg2Al-UD-LDH) nanosheets and their application as adsorbent toward arsenate immobilization. Colloidal LDH nanosheets featured the absence of nanoparticles release in the environment differently from other nanomaterials. The adsorption studies conducted in batch method, revealed that colloidal Mg2Al-UD-LDH nanosheets (obtained by ultrasonic treatment of Mg2Al-NO3-LDH suspension) achieved a higher arsenate adsorption density of 1.21 mmol/g than parent Mg2Al-NO3-LDH (1.16 mmol/g) at a solid-to-solution dosage of 0.78 g LDH/L. The adsorption mechanism of arsenate onto colloidal Mg2Al-UD-LDH nanosheets proceeded through restacking of the nanosheets, besides ion-exchange onto Mg2Al-NO3-LDH and surface adsorption onto Mg2Al-CO3-LDH. Kinetics of arsenate adsorption onto colloidal Mg2Al-UD-LDH nanosheets was rapid, reaching equilibrium within 5 min, whereas equilibrium was reached within 120 min in the presence of Mg2Al-NO3-LDH. The colloidal LDH nanosheets stacking effect was restricted at higher LDH/As ratios owing to electrostatic repulsion among the nanosheets, as determined by zeta potential measurements. Semi-pilot scale static model systems for arsenate adsorption were examined to further investigate the adsorption performance of colloidal Mg2Al-UD-LDH nanosheets in natural water systems such as river, pond, or lake. Arsenate adsorption was rapid onto colloidal Mg2Al-UD-LDH nanosheets owing to their high dispersibility; specifically, 100% adsorption efficiency was achieved within 5 min. Thus, the high adsorption capacity, dispersibility, and fast kinetics of arsenate removal onto colloidal Mg2Al-UD-LDH nanosheets promising for use as an efficient adsorbent for water remediation..
170. Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki, Effects of hydrothermal treatment coupled with mechanical expression on combustion performance of Loy Yang lignite, Journal of Thermal Analysis and Calorimetry, 10.1007/s10973-016-5692-3, 126, 3, 1925-1935, 2016.12, The combustion characteristics and kinetics of hydrothermal treatment (HT) without addition of extra water and of HT coupled with mechanical expression (HT–ME) were investigated using thermogravimetric analysis at various heating rates. The relationships between various physicochemical properties, i.e., amounts of volatile matter and fixed carbon, specific surface area, and pore volume, and combustion performance were also investigated. The activation energy was calculated using the Kissinger–Akahira–Sunose isoconversional method. The results showed that for samples treated using HT and HT–ME, the ignition temperatures and temperatures at which the mass loss rates were at maximum, mainly because of char combustion, were significantly higher than those for raw lignite. They increased slightly with increasing processing temperature, suggesting that HT and HT–ME decrease the reactivity of Loy Yang lignite. The maximum combustion rates of the treated samples were higher than those of raw lignite and the values for the HT and HT–ME samples differed slightly from each other. The higher maximum combustion rates indicate that HT and HT–ME modify the combustion intensity of Loy Yang lignite. Furthermore, the combustion of raw lignite can be described by multistep kinetics, whereas single rate-limiting step kinetics can be used to describe the kinetics of the other samples. Average activation energies of samples treated using HT and HT–ME at 200 °C reached the maximum values..
171. Yu Takaki, Xinhong Qiu, Tsuyoshi Hirajima, Keiko Sasaki, Removal mechanism of arsenate by bimetallic and trimetallic hydrocalumites depending on arsenate concentration, Applied Clay Science, 10.1016/j.clay.2016.05.010, 134, 26-33, 2016.12, We investigated the influence of initial arsenate concentration (C0) in the 5th order of magnitude on removal of arsenate by hydrocalumite (bimetallic layered double hydroxide, LDH) and Mg-doped hydrocalumite (trimetallic LDH) from aqueous solution. These hydrocalumites were prepared by the microwave-assisted hydrothermal treatment. There is a trend that the larger adsorption density of arsenate (Qe) values is observed with bimetallic LDH under low C0 values and with trimetallic LDH under high C0 values. The transitional C0 values ranged at 2.10–2.96 mM. Comprehensively understanding characterization results for the solid residues after adsorption of arsenate by X-ray diffraction, 27Al-nuclear magnetic resonance, and scanning electron microscopy–energy dispersive X-ray, the mechanism to remove arsenate was dependent on arsenate concentrations. At low arsenate concentration, partial intercalation and dissolution–reprecipitation (DR) happened together. With increasing C0, full intercalation and DR happened to bring out one phase of arsenate-bearing hydrocalumite. Under the very high C0, DR mechanism happened at the edge sites of LDH sheets, leading that the newly formed massive precipitates block the further intercalation with nitrate. As a result, two phases of LDH were observed. The greater Qe with bimetallic LDH in low concentration comes from high crystallinity to enhance partial ion-exchange, and greater Qe with trimetallic LDH in high concentration is derived from more fragile properties to enhance DR mechanism..
172. Hajime Miki, Tsuyoshi Hirajima, Kazunori Oka, Keiko Sasaki, The development of fine microgram powder electrode system and its application in the analysis of chalcopyrite leaching behavior, Minerals, 10.3390/min6040103, 6, 4, 2016.12, An electrode system to study the mechanism of fine microgram powder sulfide mineral dissolution was developed by using a relatively simple method that enables the attachment of micrograms of fine powder to a platinum plate surface. This system yields highly reproducible results and is sensitive compared with conventional electrode systems for various sulfide minerals such as pyrite, chalcopyrite, chalcocite, enargite, and tennantite. The leaching behavior of chalcopyrite was re-examined in a test of the application of this electrode system. Chalcopyrite dissolution is enhanced in specific potential regions because it is believed to be reduced to leachable chalcocite, but this result is inconclusive because it is difficult to detect the intermediate chalcocite. Powder chalcopyrite in the new powder electrode system was held at 0.45 V in the presence of copper ion and sulfuric acid media followed by an application of potential in the anodic direction. Besides the chalcopyrite oxidation peak, a small peak resulted at ~0.55 V; this peak corresponds to reduced chalcocite, because it occurs at the same potential as the chalcocite oxidation peak..
173. Sayo Moriyama, Keiko Sasaki, Tsuyoshi Hirajima, Effect of freeze drying on characteristics of Mg–Al layered double hydroxides and bimetallic oxide synthesis and implications for fluoride sorption, Applied Clay Science, https://doi.org/10.1016/j.clay.2016.07.016, Vol.132-133, 460-467, 2016.11.
174. Sayo Moriyama, Keiko Sasaki, Tsuyoshi Hirajima, Effect of freeze drying on characteristics of Mg–Al layered double hydroxides and bimetallic oxide synthesis and implications for fluoride sorption, Applied Clay Science, 10.1016/j.clay.2016.07.016, 132-133, 460-467, 2016.11, In this study, freeze-drying was applied in the synthesis of nanocrystalline layered double hydroxides (LDHs), and the properties of resulting LDHs along with their efficacies for the removal of fluoride were evaluated. Nanocrystalline NO3- and Cl-type LDHs were produced by freeze-drying using liquid N2. The solid properties of the freeze-dried LDHs were compared with those of LDHs dried at 100 °C. Both NO3- and Cl-type LDHs were analyzed via X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy (SEM). XRD analysis confirmed that the LDHs dried by liquid N2 were hydrotalcite-like compounds with lower degrees of crystallinity compared with those dried at 100°C. SEM images showed agglomerated nanoparticles in the freeze-dried LDHs. No significant difference was observed between the NO3- and Cl-type LDHs. However, all characterization results suggested that the freeze-drying method resulted in small nanoparticle sizes. Moreover, bimetallic oxides produced by the calcination of LDHs were affected by the crystallinities of starting materials. Fluoride (F) sorption experiments on the synthesized LDHs indicated that the freeze-dried LDHs and resulting bimetallic oxides were better sorbents compared with the LDHs prepared at 100 °C. The sorption capacities of F on the LDHs and bimetallic oxides from freeze drying were 0.78–0.87 mM and 4.34 mM, respectively..
175. Paulmanickam Koilraj, Siwaporn Meejoo Smith, Qianqian Yu, Sarah Ulrich, Keiko Sasaki, Encapsulation of a powdery spinel-type Li+ ion sieve derived from biogenic manganese oxide in alginate beads, Powder Technology, 10.1016/j.powtec.2016.08.009, 301, 1201-1207, 2016.11, A powdery lithium ion sieve (HMO) derived from biogenic birnessite was homogeneously integrated in sodium alginate (AL) beads. The composite beads were then characterized and their Li+ adsorption properties were investigated. Scanning electron microscopy–energy dispersive spectroscopy analysis showed that the HMO particles were homogeneously dispersed in the AL beads even after drying. The adsorption isotherm of Li+ adsorption to HMO encapsulated in AL beads (HMO–AL) was well fitted by the linear Langmuir model, and the beads showed a maximum adsorption capacity of 3.61 mmol/g based on HMO, which is comparable with the value of the original powdery HMO. Kinetic studies revealed that adsorption of Li+ follows a pseudo-second-order model with rate constant k2 = 2.8–11.9 × 10− 3 g/(mmol min) for the initial Li+ concentration range 2.56–4.23 mM. Diffusion of Li+ from aqueous solution to the HMO particle through the Ca–AL network is the rate-limiting step for Li+ adsorption to HMO–AL beads. The HMO-AL beads enhanced the handling efficiency for Li+ adsorption and reused without significant reduction of Li+ adsorption efficacy..
176. Qianqian YU, Sasaki Keiko, Microwave-assisted hydrothermal synthesis of nanocrystalline lithium-ion sieve from biogenic manganese oxide, its characterization and lithium sorption studies, Hydrometallurgy, 10.1016/j.hydromet.2015.10.002, Vol.165, Part1, 118-124, 165 (2016) 118–124, 2016.10.
177. Chenyang Li, Lazaro Calderin, Sasaki Keiko, Ismaila Dabo, First-principles Study of the Removal of Boron by Co-precipitation with Hydroxyapatite Using Dolomite as a Starting Material, Bulletin of the American Physical Society, 2016.10.
178. Xiangchun Liu, Taigen Masuyama, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki, Combustion performance of Loy Yang lignite treated using microwave irradiation treatment, Thermochimica Acta, 10.1016/j.tca.2016.09.010, 642, 81-87, 2016.10, The combustion characteristics and activation energy of the microwave irradiation (MI) treated lignite were investigated by thermogravimetric analysis at different heating rates. Effects of the changes in physicochemical properties (amounts of volatile matter and fixed carbon, specific surface area, and pore volume) on the combustion performance were also discussed. The activation energy was calculated using the Kissinger–Akahira–Sunose isoconversional method. The results showed that ignition temperature of the MI treated samples increased significantly relative to that of raw lignite, and it gradually increased with increasing MI time, indicating that MI treatment decreases the reactivity of lignite, which progressively decreases as MI time increases. The maximum combustion rates of the treated samples were higher than that of raw lignite, suggesting that MI treatment modifies the combustion intensity of Loy Yang lignite. Moreover, the combustion processes of samples treated by MI for 5 and 7 min were single rate-limiting step kinetics, whereas raw lignite and samples treated by MI for 3 and 9 min followed multistep kinetics. Average activation energy for sample treated using MI for 5 min was the maximum value, and it decreased with further increasing MI time because of the increased effect of diffusion..
179. Wuhui Luo, Akihiro Inoue, Tsuyoshi Hirajima, Keiko Sasaki, Sequential modification of montmorillonite with dimethyl dioctadecyl ammonium chloride and benzyl octadecyl dimethyl ammonium chloride for removal of perchlorate, Microporous and Mesoporous Materials, 10.1016/j.micromeso.2015.12.030, 233, 117-124, 2016.10, A novel method is reported for surfactant modification of montmorillonite (Mt), and then the performance of the surfactant-modified Mt was investigated for the removal of perchlorate (ClO4
). Mt was first modified with dimethyl dioctadecyl ammonium chloride (DDAC) under microwave irradiation, which was followed by a second modification with benzyl octadecyl dimethyl ammonium chloride (BODAC). The influence of the added amount of DDAC in terms of ClO4
adsorption to the modified Mt was intensively investigated. In addition, sequential and simultaneous-mixing methods were compared for preparation of the modified Mt in terms of ClO4
removal performance. Using sequential modification, addition of DDAC corresponding to 0.05 times the cation exchange capacity of Mt significantly increased BODAC uptake, resulting in the highest adsorption capacity for ClO4
(1.08 mmol/g). This can be explained by the good balance between the decrease of steric hindrance and the formation of a hydrophobic interface because of adsorbed DDAC. In contrast, for a composite synthesized with the same ratio of DDAC to BODAC, the simultaneous-mixing method resulted in modified Mt with much poorer ClO4
removal performance than the sequential modification method because of the negligible contribution of DDAC to BODAC uptake by Mt. Moreover, a high binding affinity of ClO4
to the sequentially modified composite was obtained because of hydrophobicity of interlaced alkyl chains..
180. Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki, Hydrothermal treatment coupled with mechanical expression for Loy Yang lignite dewatering and the microscopic description of the process, Drying Technology, 10.1080/07373937.2015.1127933, 34, 12, 1471-1483, 2016.09, The changes in the gaseous, liquid, and solid products obtained from hydrothermally treated lignite and hydrothermally treated solid products treated by the following mechanical expression were investigated. Furthermore, a microscopic description of the changes was present. Gaseous, liquid, and solid products were characterized by gas chromatography, total organic carbon analyzer, inductively coupled plasma atomic emission spectroscopy, high-performance liquid chromatography, and Fourier transform infrared spectrometer, respectively. The results showed that at temperatures above 173°C for hydrothermal treatment, freezable water, and some organic and inorganic compounds were removed from lignite, and acidic groups first dissolved and decomposed at 100°C. For the following mechanical expression treatment, freezable and nonfreezable water and organic and inorganic compounds were removed, and the concentration of acidic groups changed little. Within temperatures range 175–250°C, for hydrothermal treatment, nonfreezable water and inorganic and organic compounds continued to be removed, and the detection of CO2 is because of decarboxylation. For the following mechanical expression treatment, the main removed water was nonfreezable water, and changes in organic and inorganic compounds, acidic groups, and volatile matter were similar to that of samples treated by mechanical expression at temperatures below 173°C..
181. Keiko Sasaki, Kenta Toshiyuki, Keiko Ideta, Jin Miyawaki, Tsuyoshi Hirajima, Interfacial effects of MgO in hydroxylated calcined dolomite on the co-precipitation of borates with hydroxyapatite, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2016.05.044, 504, 1-10, 2016.09, Hydroxylated calcined dolomite (HCD) is used as a mineralizer to immobilize borates by co-precipitation with hydroxyapatite (HAp). HCD sometimes includes appreciable quantities of MgO depending on the degree of hydroxylation of the calcined dolomite. In this work, the interfacial effects of MgO in HCD on the removal kinetics of borates were examined using Ca(OH)2 and HCDs with different degrees of hydroxylation. As the fraction of MgO phases within the HCD increased, the borate immobilization rate stagnated because the formation of hydroxyapatite (HAp) was inhibited. This effect arose from the interaction of boric acid (H3BO3) with the MgO in HCD, followed by hydroxylation to cover the Ca(OH)2 surfaces with newly formed Mg(OH)2. In the presence of borate, the unstable intermediate [MgB(OH)4]+ complex was formed through ligand-promoted dissolution of MgO in the HCD. 11B NMR spectra revealed that the stagnation in immobilization of tetragonal boron ([4]B) species was observed for up to 45 min, accompanied by the suppression of HAp formation. TEM images of the HCD suggested that Ca(OH)2 was partially associated with MgO and Mg(OH)2 phases within the HCD and hydroxylation of MgO led to a thin covering of the surface of Ca(OH)2 with the newly formed gel phases comprising Mg(OH)2/H3BO3 that hinders the dissolution of Ca(OH)2. However, when MgO was completely hydroxylated in the HCD this delay was not observed. This was supported by zeta potential measurements on the solid residues during co-precipitation. The results suggest that the degree of hydroxylation of the calcined dolomite in HCD markedly influences the co-precipitation kinetics of borates in industrial water treatment..
182. Naoko Okibe, Masashi Maki, Daisuke Nakayama, Keiko Sasaki, Microbial recovery of vanadium by the acidophilic bacterium, Acidocella aromatica, Biotechnology letters, 10.1007/s10529-016-2131-2, 38, 9, 1475-1481, 2016.09, Objective: To investigate the bioreduction of toxic pentavalent vanadium [vanadate; V(V)] in the acidophilic, Fe(III)-reducing obligately heterotrophic bacterium, Acidocella aromatica PFBC. Results: Although the initial lag-phase of growth became extended with increasing initial V(V) concentrations, the final cell density during aerobic growth of A. aromatica PFBC was unaffected by up to 2 mM V(V). While strain PFBC is an aerobe, growth-decoupled PFBC cell suspensions directly reduced V(V) using fructose, both micro-aerobically and anaerobically, under highly acidic (pH 2) and moderately acidic (pH 4.5) conditions. Bio reduced V(IV) was subsequently precipitated even under micro-aerobic conditions, mostly by encrusting the cell surface. An anaerobic condition at pH 4.5 was optimal for forming and maintaining stable V(IV)-precipitates. Recovery of approx. 70 % of V(V) from the solution phase was made possible with V(V) at 1 mM. Conclusions: The first case of direct V(V) reducing ability and its subsequent V recovery from the solution phase was shown in acidophilic prokaryotes. Possible utilities of V(V) bioreduction in acidic conditions, are discussed..
183. KOILRAJ PAULMANICKAM, Siwaporn Meejoo Smith, Qianqian Yu, Taichi Momoki, Sarah Ulrich, Sasaki Keiko, Encapsulation of powdery spinel type of Li+ ion sieve derived from biogenic manganese oxide in alginate beads, Powder Technology, http://dx.doi.org/10.1016/j.powtec.2016.08.009, 301 (2016) 1201–1207, 2016.08.
184. Sasaki Keiko, Kenta Toshiyuki, Keiko Ideta, Jin Miyawaki, Tsuyoshi Hirajima, Interfacial effects of MgO in hydroxylated calcined dolomite on the co-precipitation of borates with hydroxyapatite, Colloids and Surfaces A: Physicochemical and Engineering Aspects, doi.org/10.1016/j.colsurfa.2016.05.044, 504 (2016) 1–10, 2016.07.
185. Xiangchun Liu, Tsuyoshi Hirajima, Sasaki Keiko, Effects of hydrothermal treatment coupled with mechanical expression on combustion performance of Loy Yang lignite, Journal of Thermal Analysis and Calorimetry, 2016.07.
186. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Ahmed Mohamed Elmahdy, Hajime Miki, Keiko Sasaki, Effect of kerosene emulsion in MgCl2 solution on the kinetics of bubble interactions with molybdenite and chalcopyrite, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2016.04.039, 501, 98-113, 2016.07, The formation of stable bubble-particle aggregates is essential to the froth flotation process. To form such aggregates, bubbles and particles must collide, the intervening liquid film must be drained below its critical rupture thickness, and three-phase contact (TPC) formation must occur. A good understanding of the interaction mechanism between bubbles and particles during collision and attachment is important. We herein investigated the effects of emulsified kerosene in a 0.01 M MgCl2 solution (a model seawater component) on bubble interactions with pure molybdenite (MoS2) and chalcopyrite (CuFeS2) surfaces. In 0.01 M MgCl2 at pH 6 and 11, kerosene retarded the bubble surface mobility and reduced the bubble rise velocity. In the presence of kerosene at pH 6, the TPC formed more rapidly on both mineral surfaces. This was due to the increase in surface hydrophobicity caused by kerosene. In addition, TPC formation was more rapid on the molybdenite surface than on the chalcopyrite surface due to the effect of the adsorbed kerosene and the low surface homogeneity of molybdenite. Finally, floatability tests demonstrated that the separation of molybdenite and chalcopyrite should be possible by adding emulsified kerosene in a 0.01 M MgCl2 solution at pH 9..
187. Hajime Miki, Tsuyoshi Hirajima, Sasaki Keiko, Catalytic effect of silver on arsenic-containing copper sulfide dissolution in acidic solution, Hydrometallurgy, https://doi.org/10.1016/j.hydromet.2016.02.007, Vol.162, 1-8, 2016.06.
188. KOILRAJ PAULMANICKAM, Yu Takaki, Sasaki Keiko, Adsorption characteristics of arsenate on colloidal nanosheets of layered double hydroxide, Applied Clay Science, 134 (2016) 110–119, 2016.06.
189. Tsuyoshi Hirajima, Gde Pandhe Wisnu Suyantara, Hajime Miki, Sasaki Keiko, Effect of Mg2+ and Ca2+ as divalent seawater cations on the floatability of molybdenite and chalcopyrite, Minerals Engineering, 96–97 (2016) 83–93, 2016.06.
190. Tsuyoshi Hirajima, Takao Hagino, Sasaki Keiko, Recovery and Upgrading of Phosphorus from Digested Sewage Sludge as MAP by Physical Separation Techniques, Journal of Environmental Protection, doi.org/10.4236/jep.2016.76074, 7, 816-824, 2016.06.
191. Hajime Miki, Akinobu Iguchi, Tsuyoshi Hirajima, Keiko Sasaki, Catalytic effect of silver on arsenic-containing copper sulfide dissolution in acidic solution, Hydrometallurgy, 10.1016/j.hydromet.2016.02.007, 162, 1-8, 2016.06, Catalytic effects of silver on the dissolution of arsenic-containing copper sulfides such as enargite in acidic media were investigated. Leaching experiments showed that silver increased the enargite dissolution rate, and that the dissolution behavior was potential-dependent. The addition of silver ions and silver sulfide greatly enhanced enargite dissolution. Such behavior can be explained based on the following reaction model: enargite dissolution is enhanced by silver as the silver ions remove the hydrogen sulfide produced during enargite reduction, giving the more amenable copper sulfide. Thermodynamic calculations suggested that the addition of silver ions and controlling the potential would maintain a high enargite dissolution rate. Leaching experiments were therefore performed with the addition of silver sulfide and potential control using an automatic titration apparatus. Experimental results showed that a combination of these two factors gave high enargite dissolution; i.e., 75% copper was dissolved in 24 h at 0.750-0.850 V vs. the standard hydrogen electrode at 303 K..
192. Yu Takaki, Xinhong Qiu, Tsuyoshi Hirajima, Keiko Sasaki, Removal mechanism of arsenate by bimetallic and trimetallic hydrocalumites depending on arsenate concentration, Applied Clay Science, 134 (2016) 26–33, 2016.05.
193. Naoko Okibe, Yusei Masaki, Daisuke Nakayama, Sasaki Keiko, Microbial recovery of vanadium by the acidophilic bacterium, Acidocella aromatic, Biotechnology Letters, DOI: 10.1007/s10529-016-2131-2, 38:1475–1481, 2016.05.
194. Widi Astuti, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe, Comparison of atmospheric citric acid leaching kinetics of nickel from different Indonesian saprolitic ores, Hydrometallurgy, 10.1016/j.hydromet.2015.12.015, 161, 138-151, 2016.05, Saprolitic ores from Sulawesi Island (SS ore) contain serpentine and goethite as major minerals, whereas the main minerals in saprolitic ore from Halmahera Island (SH ore) are talc and goethite. Most of the nickel was incorporated in a magnesium-silica-containing mineral. The effects on nickel extraction of leaching temperature, citric acid concentration, and ore particle size were determined to investigate the leaching performances and leaching kinetics of the two saprolitic ores. Nickel leaching efficiency from SS ore is always higher than that from SH ore under the same leaching conditions. The mineral contents of the ores significantly affected the leaching performances and mineral dissolution behaviors of the samples. The results of nickel leaching efficiency and analysis of the solid residues suggest that all dissolved nickel originated from serpentine, which is more easily leached than goethite and talc. The rate of nickel extraction for SS ore was faster than that for SH ore. Nickel leaching from SS ore and SH ore followed the shrinking-core model and was controlled by diffusion of a reactant or product through the solid product layer..
195. Tomoyo Goto, Keiko Sasaki, Synthesis of morphologically controlled hydroxyapatite from fish bone by urea-assisted hydrothermal treatment and its Sr2+ sorption capacity, Powder Technology, 10.1016/j.powtec.2016.01.041, 292, 314-322, 2016.05, Needle- and sponge-shaped hydroxyapatite (HAp) particles were synthesized from calcined tuna fish bone (Tn1000) and commercially available HAp reagent (ChemHAP) by a urea-assisted hydrothermal treatment using 0.1-1.0 M urea solution at 160 °C for 3 h. The Sr2+ sorption capacity of the synthesized HAp was also investigated using 0-50 mM Sr2+ solution at 25 °C for 72 h to evaluate its performance as a sorbent for environmental remediation. Sponge-shaped HAp was formed under hydrothermal conditions with a urea concentration of 1.0 M. With decreasing urea concentration, the morphology of HAp changed from sponge-shaped to needle-shaped crystals, regardless of the starting material. Some calcium carbonate and/or β-tricalcium phosphate impurities were formed from Tn1000 at 0.1-0.5 M urea concentration. The Sr2+ sorption mechanism of the synthesized HAp was estimated using Ca ion-exchange reaction and precipitation of SrCO3. The sponge-shaped HAp crystals, which had high specific surface area and CO3 2- content, exhibited a large ion-exchange capacity with Sr2+. In contrast, the ion-exchange ratio of needle-shaped HAp dramatically decreased with increasing initial Sr concentration. No clear difference in Sr2+ sorption behaviour caused by the choice of HAp synthesis starting material was observed. These results indicate that the Sr sorption mechanism of HAp is influenced by not only its composition but also its crystal morphology..
196. Wuhui Luo, Tsuyoshi Hirajima, Sasaki Keiko, Optimization of Hexadecylpyridinium-modified Montmorillonite for Removal of Perchlorate Based on Adsorption Mechanisms, Applied Clay Science, https://doi.org/10.1016/j.clay.2016.01.005, Vol.123, 29-36, 2016.04.
197. Dewi Agustina Iryani, Sasaki Keiko, Tsuyoshi Hirajima, HYDROTHERMAL CARBONIZATION KINETICS OF SUGARCANE BAGASSE TREATED BY HOT COMPRESSED WATER UNDER VARIABEL TEMPERATURE CONDITIONS, ARPN Journal of Engineering and Applied Sciences, 11, 7, 4833-4839, 2016.04.
198. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Sasaki Keiko, EFFECT OF KEROSENE EMULSION IN MgCl2 SOLUTION ON THE KINETICS OF BUBBLE INTERACTION WITH MOLYBDENITE AND CHALCOPYRITE, Colloids and Surfaces A: Physicochemical and Engineering Aspects, in press., 501 (2016) 98–113, 2016.04.
199. Yusei Masaki, Masashi Maki, Daisuke Nakayama, Sasaki Keiko, Naoko Okibe, Microbial recovery of vanadium by Fe(III)-reducing, acidophilic bacterium, Acidocella aromatica PFBC, Biotechnology Letters, 2016.04.
200. Xiangchun Liu, Tsuyoshi Hirajima, Sasaki Keiko, Effect of hydrothermal treatment coupled with mechanical expression on equilibrium water content of Loy Yang lignite and mechanism, Mater. Trans., in press., 2016.04.
201. Airi Harada, Keiko Sasaki, Takashi Kaneta, Direct determination of lignin peroxidase released from Phanerochaete chrysosporium by in-capillary enzyme assay using micellar electrokinetic chromatography, Journal of Chromatography A, 10.1016/j.chroma.2016.02.062, 1440, 145-149, 2016.04, Here we describe the application of an in-capillary enzyme assay using micellar electrokinetic chromatography (MEKC) in the determination of enzyme activity in a crude culture medium containing lignin peroxidase released from Phanerochaete chrysosporium (P. chrysosporium). The method consists of a plug-plug reaction between lignin peroxidase and its substrate, veratryl alcohol, the separation of the product, veratraldehyde, from the other components including the enzyme and the culture medium, and the determination of the enzyme activity from the peak area of veratraldehyde produced by the plug-plug reaction. This method is more sensitive than conventional spectrophotometry since the background originates from the enzyme and the culture medium can be removed via MEKC separation. Veratraldehyde was separated at -10 kV in a background electrolyte containing 50 mM tartrate buffer (pH 2.5) and 50 mM sodium dodecyl sulfate (SDS) after a plug-plug reaction in the capillary for 5 min. The calibration curve of veratraldehyde was linear up to 4 pmol (500 μM) with a limit to quantification of 0.026 pmol (3.2 μM) (SN = 10). The activity of lignin peroxidase was directly measured from the peak area of veratraldehyde. The activity of lignin peroxidase released from P. chrysosporium into the medium for 7 days was successfully determined to be 3.40 UL-1..
202. Dewi Agustina Iryani, Satoshi Kumagai, Moriyasu Nonaka, Keiko Sasaki, Tsuyoshi Hirajima, Hydrothermal carbonization kinetics of sugarcane bagasse treated by hot compressed water under variabel temperature conditions, ARPN Journal of Engineering and Applied Sciences, 11, 7, 4833-4839, 2016.04, This study investigated kinetics of hydrothermal carbonization (HTC) decomposition reaction of sugarcane bagasse treated with hot compressed water under varied temperature in range 200-300 °C. Experiments were carried out using a batch type reactor with a temperature controller. Characterization results showed that the decomposition reaction was influenced by temperature and reaction time. Degradation of hemicellulose began at 200°C (3 min) and was completed at 240°C (5 min) to form arabinose and xylose. Cellulose started to decompose at 240°C (5 min) and was completely degraded at 270°C (20 min). Lignin decomposed at temperature range 200-300°C, and produced aromatic and phenolic compounds. The kinetics calculation for decomposition reactions such as hydrolysis and dehydration reactions are adopted as the heterogeneous reaction model. The model assumes that solid particle is cylindrical shape and this size is shrinking with reaction (cylindrical shrinking core model). Results of calculation indicated that the reaction is controlled with the diffusion through product layer. From these calculation and the results of decomposition mechanism can be explained as follows: (i) hydrothermal carbonization cellulose and hemicellulose are decomposed preferentially and un-reacted lignin part to be diffusion layer. (ii) the hydrolysis and dehydration reaction started at 200°C and 240°C respectively and reaction rate increased with increasing temperature..
203. Wuhui Luo, Tsuyoshi Hirajima, Keiko Sasaki, Optimization of hexadecylpyridinium-modified montmorillonite for removal of perchlorate based on adsorption mechanisms, Applied Clay Science, 10.1016/j.clay.2016.01.005, 123, 29-36, 2016.04, Adsorption of perchlorate (ClO4 -) onto hexadecylpyridinium-modified montmorillonite (OMt) was investigated by in situ and ex situ methods. For the in situ method, ClO4 - was initially bound by hexadecylpyridinium (HDPy+) in the form of HDPy-ClO4 which together with the excess HDPy+ were simultaneously captured by Mt. The ex situ strategy was performed by adding synthesized OMt into ClO4 --bearing solution, where conventionally dried OMt (II-OMt) and innovative OMt (I-OMt) without drying and washing procedure were compared as adsorbents. The adsorption capacity of ClO4 - and amount of HDPy released into equilibrium solution were evaluated, where surfactant release was rarely addressed in previous publications. I-OMt showed relatively high adsorption capacity of ClO4 - and negligible release of HDPy. The lower adsorption capacity of ClO4 - onto II-OMt was caused by the washing procedure which removed the unstably anchored HDPy. Inhibition of HDPy release of I-OMt was explained by reconfiguration of HDPy after ClO4 - adsorption as supported by results of X-ray diffraction and attenuated total reflection Fourier transform infrared spectroscopy. In addition, for anion adsorption onto conventionally synthesized OMt, the difference between the amounts of released counter ion and that of entrapped target anion is generally ignored. Such phenomenon was critically considered in this study, and the results showed that the difference between adsorbed ClO4 - and released Cl- decreased with an increase of HDPy loading and was more significant in I-OMt. This is rationalized by the desorption of HDPy+ and formation of HDPy-ClO4 according to the results of 13C nuclear magnetic resonance spectra and the adsorption energy evaluated by the Dubinin-Radushkevich model..
204. Paulmanickam Koilraj, Keiko Sasaki, Fe3O4/MgAl-NO3 layered double hydroxide as a magnetically separable sorbent for the remediation of aqueous phosphate, Journal of Environmental Chemical Engineering, 10.1016/j.jece.2016.01.005, 4, 1, 984-991, 2016.03, The separation of a spent sorbent from treated water after remediation is one of the major difficulties associated with industrial scale water treatment methods. Fe3O4 particles offer an easy magnetic method for the separation of used sorbent from water. Due to its low sorption capacity, magnetic Fe3O4 particles were first modified with Mg2Al-NO3-LDH prior to use in phosphate remediation. The Fe3O4/Mg2Al-NO3-LDH composite materials showed a maximum sorption capacity of 33.4 mgP/g while Fe3O4 particles alone recovered only 4.6 mgP/g. The kinetics of phosphate sorption onto Fe3O4/Mg2Al-NO3-LDH follows the pseudo-second order kinetic model supported by the best linear regression coefficient value (R2 - 1.00). Sorption isotherm studies indicated that it follows the Langmuir monolayer sorption isotherm. The effect of pH and competing anion studies indicate that this material is highly efficient in a wide pH range (pH 3-10). Selective sorption of phosphate on Fe3O4/Mg2Al-NO3-LDH was observed in the presence of excess sulfate, as well as from sea water enriched with phosphate. Fe3O4/Mg2Al-NO3-LDH composite material offers easy separation of spent sorbents due to magnetic property. The retention of sorption capacity in a wide pH range, and selectivity in the presence of competing anion, as well as from sea water suggests that these composite magnetic materials will be effective for wastewater remediation..
205. Keiko Sasaki, Kenta Toshiyuki, Keiko Ideta, Hajime Miki, Tsuyoshi Hirajima, Jin Miyawaki, Mitsuhiro Murayama, Ismaila Dabo, Removal mechanism of high concentration borate by co-precipitation with hydroxyapatite, Journal of Environmental Chemical Engineering, 10.1016/j.jece.2016.01.012, 4, 1, 1092-1101, 2016.03, Co-precipitation of borate in a wide range of concentration with hydroxyapatite (HAp) was investigated using Ca(OH)2 as a mineralizer in the presence of phosphate. The sorption data of borate was fitted to Freundlich model. The maximum sorption density of B/Ca to maintain a mono-phase of HAp was found around 0.40. In higher B concentrations, borate was still immobilized, however, the crystalization of hydroxyapatite was inhibited, where the solid residues were accompanied with amorphous CaB2O4, as well as HAp. Based on 11B-NMR and elemental analysis for solid residues in addition to solution chemistry, the removal mechanism of high concentration borate can be explained by the surface complexation of triborate on Ca(OH)2, subsequently decomposition of triborate into monoborate to release [CaB(OH)4]+ and B(OH)4 -, followed by co-precipitation with HAp. These tetragonal B species were immobilized in the solid residues including amorphous HAp. During the process there was a trend to eliminate carbonate from the solid phase. TEM images suggested that the HAp particles precipitated at room temperatures were in a fibrous shape consisting of a number of short rods when borate species are not added. When borate species were immobilized, the HAp particles have gotten swelled with losing fibrous shapes. When further higher borate concentrations were encapsulated in co-precipitated products, the morphologies were dramatically changed, that is, nano-sized and less crystalline HAp particles were enveloped by possibly amorphous CaB2O4..
206. Airi Harada, Sasaki Keiko, Takashi Kaneda, Direct Determination of Lignin Peroxidase Released from Phanerocheate chrysosprium by In-Capillary Enzyme Assay Using Micellar Electrokinetic Chromatography, Journal of Chromatography A, 1440 (2016) 145–149, 2016.02.
207. Tomoyo Goto, Sasaki Keiko, Synthesis of morphologically controlled hydroxyapatite from fish bone by urea-assisted hydrothermal treatment and its Sr2+ sorption capacity, Powder Technology, 292, 314-322, 2016.02.
208. KOILRAJ PAULMANICKAM, Sasaki Keiko, Fe3O4/MgAl-NO3 layered double hydroxide as magnetically separable sorbent for the remediation of aqueous phosphate, J. Environ. Chem. Engng., http://dx.doi.org/10.1016/j.jece.2016.01.005, 4, 984-991, 2016.01.
209. Sasaki Keiko, Tsuyoshi Hirajima, Kenta Toshiyuki, Dabo Ismaila, Mistuhiro Murayama, Removal mechanism of high concentration borate by co-precipitation with hydroxyapatite, Journal of Environmental Chemical Engineering, http://dx.doi.org/10.1016/j.jece.2016.01.012, 4, 1092-1101, 2016.01.
210. Wuhui Luo, Akihiro Inoue, Tsuyoshi Hirajima, Sasaki Keiko, Sequential modification of montmorillonite with dimethyl dioctadecyl ammonium chloride and benzyl octadecyl dimethyl ammonium chloride for removal of perchlorate, Microporous Mesoporous Materials, http://dx.doi.org/10.1016/j.micromeso.2015.12.030, 233 (2016) 117-124, 2016.01.
211. Widi Astuti, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe, Comparison of effectiveness of citric acid and other acids in leaching of low-grade Indonesian saprolitic ores, Minerals Engineering, 10.1016/j.mineng.2015.10.001, 85, 1-16, 2016.01, Comparison effect of chemical citric acid and other leaching reagents including inorganic acid and other organic acid on nickel extraction from low-grade Indonesian saprolitic ores was evaluated. Two saprolitic ores from two different mining areas (Sulawesi Island and Halmahera Island) in Indonesia were used to investigate the leaching performance and mineral dissolution behaviors of different ore samples using different leaching reagents. Leaching was performed using citric, sulfuric, nitric, hydrochloric, lactic, and oxalic acids. The saprolitic ore from Sulawesi Island (SS) has higher serpentine and lower goethite contents than the saprolitic ore from Halmahera Island (SH). These differences significantly affect the leaching performances and metal dissolution behaviors. Citric acid and sulfuric acid were more effective than other acid solutions for nickel extraction from both samples. Citric acid was very effective for dissolving nickel from serpentine, but did not recover nickel from goethite. In contrast, inorganic acids, namely sulfuric, nitric, and hydrochloric acids, can extract nickel from lateritic ores by dissolving goethite as well as serpentine, but the nickel recoveries achieved with sulfuric acid were higher than those achieved with other inorganic acids. A comparison of the leaching performances of the two samples shows that nickel recovery from SS was higher than that from SH when citric acid leaching was used, but the samples gave similar nickel recoveries in all inorganic acid and lactic acid leaching processes. Moreover, oxalic acid is the least effective reagent for nickel extraction from both samples, because of nickel oxalate precipitation after nickel dissolution. In addition, the effect of a sulfuric acid-citric acid mixture on the nickel dissolution rate was investigated to confirm the individual influences of citric acid and sulfuric acid on the leaching behavior of each sample. The results show that an increase in the amount of sulfuric acid affected the dissolution rate of nickel in leaching of SH much more than that in leaching of SS. In general, the effect of citric acid in the mixture of sulfuric acid and citric acid is attractive. Moreover, citric acid offers not only high nickel recovery and high selectivity of leaching but also an environmentally safe process and low acid consumption..
212. Tsuyoshi Hirajima, Hidekazu Matsuoka, Hajime Miki, Gde Pandhe Wisnu Suyantara, Ahmed Mohamed Elmahdy, Keiko Sasaki, Comparison of selective flotation of chalcopyrite and molybdenite with various oxidation techniques, 28th International Mineral Processing Congress, IMPC 2016 IMPC 2016 - 28th International Mineral Processing Congress, 2016.01, Selective flotation of chalcopyrite and molybdenite was studied using various surface treatment methods such as electrolysis, ozone treatment, and plasma. Oxidation via electrolysis method indicated that only chalcopyrite surface is affected by electrolysis due to conductivity difference with molybdenite. Oxidation treatments and XPS analyses indicated that chalcopyrite became hydrophilic due to deposition of oxidized iron on its surface. Various oxidizing methods also showed that chalcopyrite was selectively oxidized and this can apply selective flotation of chalcopyrite and molybdenite. The possible mechanisms are proposed in this work based on surface analyses and thermodynamic calculations..
213. Tsuyoshi Hirajima, Gde Pandhe Wisnu Suyantara, Osamu Ichikawa, Ahmed Mohamed Elmahdy, Hajime Miki, Keiko Sasaki, Effect of Mg2+ and Ca2+ as divalent seawater cations on the floatability of molybdenite and chalcopyrite, Minerals Engineering, 10.1016/j.mineng.2016.06.023, 96-97, 83-93, 2016.01, Seawater flotation has been applied to mineral processing in areas located far from fresh water resources. However, as seawater has a detrimental effect on molybdenite floatability under alkaline conditions (pH > 9.5), its application in the conventional copper and molybdenum (Cu-Mo) flotation circuit is hindered. A fundamental study of the effect of two divalent cations in seawater, Mg2+ and Ca2+, on the floatability of chalcopyrite and molybdenite is presented in this paper. Floatability tests showed that both MgCl2 and CaCl2 solutions depress the floatability of chalcopyrite and molybdenite at pH values higher than 9. Furthermore, Mg2+ exerts a stronger effect than Ca2+ owing to the adsorption of Mg(OH)2 precipitates on the mineral surfaces, as indicated by dynamic force microscopy images. The floatability of chalcopyrite was significantly depressed compared with that of molybdenite in a 10−2 M MgCl2 aqueous solution at pH 11. This phenomenon is likely due to the adsorption of hydrophilic complexes on the mineral surface, which reduces the surface hydrophobicity. A reversal of the zeta potential of chalcopyrite in MgCl2 and CaCl2 solutions at pH 11 and 8, respectively, indicated the adsorption of precipitates onto the surface. In contrast, the zeta potential of molybdenite decreased continuously under the same conditions. The floatability test of chalcopyrite and molybdenite in mixed systems showed that selective separation of both minerals should be possible with the addition of emulsified kerosene to a 10−2 M MgCl2 solution at pH 11. A mechanism is proposed to explain this phenomenon..
214. Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki, Effect of hydrothermal treatment coupled with mechanical compression on equilibrium water content of loy yang lignite and mechanism, Materials Transactions, 10.2320/matertrans.M-M2016809, 57, 6, 935-942, 2016.01, Measurements of equilibrium water contents (EWCs) in samples obtained from hydrothermal treatment (HT) and HT coupled with mechanical compression (HT-MC) were undertaken across a range of relative humidities (RHs) to investigate the performance of EWC and its mechanism. The changes in the concentrations of carboxyl groups and mesopore volume were measured by an improved barium ion exchange and N2 adsorption-desorption isotherms methods, respectively. The results showed that EWCs decreased with progressively severe HT and HT-MC conditions and EWCs of HT-MC samples were lower than those of HT samples, indicating that HT and HT-MC can upgrade lignite by reducing water loading capacity and HT-MC was better than HT. At low RHs (RH ≥ 10%), the factor that controls EWC is water moleculesactive sites interactions and one to two water molecules are associated with each carboxyl group, while at medium RHs (10 < RH ≥ 92%) the amount of monolayer water and mesopore volume gain in significance and ca. two multilayer water molecules are bound to each monolayer water molecule. At high RHs (RH > 92%), EWC is determined by comprehensive factors such as macropores and cracks. Furthermore, EWC can be either higher or lower than residual water content (RWC) based on the RH within a threshold residual water level (ca. 5 to 16%). EWC was generally higher than RWC below a RWC of ca. 5% and the opposite relationship was observed for samples with RWC above ca. 16%. These provide information for the operation of lignite dewatering technique, the control of its water re-adsorption, and storage..
215. Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, A. M. Elmahdy, Hajime Miki, Keiko Sasaki, Effect of kerosene on bubble interaction with molybdenite and chalcopyrite in MgCl2 solution, 28th International Mineral Processing Congress, IMPC 2016 IMPC 2016 - 28th International Mineral Processing Congress, 2016.01, Seawater has been reported to depress molybdenite in a copper-molybdenum (Cu-Mo) flotation process at high pH due to the precipitation of Mg(OH)2. Meanwhile, to improve mineral recoveries, collectors are usually added into the flotation cells, thus adding the complexity to the mechanism of bubble-particle interactions involved in Cu-Mo flotation. Therefore, understanding the interaction mechanism in seawater flotation and in the presence of collectors is important to explain the minerals depression. The present work investigated the effect of kerosene on the bubble collision and attachment to pure chalcopyrite and molybdenite surfaces in MgCl2 solution as one of the seawater major components at pH 6 and 11. Mineral surfaces were characterized using atomic force microscopy (AFM). In addition, minerals floatability in the same system were tested in a column flotation. The study of bubble-particle interactions shows that following several collisions, bubble could displace the intervening liquid layer on the mineral surfaces, forming a three-phase contact (TPC). A TPC formed more rapidly in the presence of emulsified kerosene in a 0.01 M MgCl2 solution at pH 6 for both minerals. The reason is kerosene increased the surfaces hydrophobicity and destabilized the intervening liquid layer on the surfaces. Moreover, the average time required to form a TPC was shorter on molybdenite surface. This can be attributed to the effect of adsorbed kerosene on molybdenite surface and molybdenite surface roughness..
216. Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Anggoro Tri Mursito, Keiko Sasaki, Use of FTIR combined with forms of water to study the changes in hydrogen bonds during low-temperature heating of lignite, Drying Technology, 10.1080/07373937.2015.1026984, 34, 2, 185-193, 2016.01, The changes in the hydrogen bonds (HBs) of three types of Indonesian lignite during low-temperature heating were investigated. The amount of water loss was determined by weighing the samples before and after heating in an oven. The changes in the number of the different types of HBs were determined using Fourier transform infrared spectroscopy coupled with types of water in lignite. The number of peak positions and absorption bands in each spectrum was determined by curve-fitting analysis with a Gaussian function. The quantified integrated area of aromatic hydrogen atoms was used to accurately investigate the changes in the HBs. The results show that at low temperatures (T ≤ 50°C), free water is mainly removed, and the HBs broken are those between free water molecules. However, at medium temperatures (50
217. Classification of the Waste Fluorescent Lamps using Signal Processing and Discriminant Analysis.
218. Mutia Dewi YUNIATI, Keitaro KITAGAWA, Tsuyoshi HIRAJIMA, Hajime MIKI, Naoko OKIBE, Keiko SASAKI, Suppression of pyrite oxidation in acid mine drainage by carrier microencapsulation using liquid product of hydrothermal treatment of low-rank coal, and electrochemical behavior of resultant encapsulating coatings, Hydrometallurgy, https://doi.org/10.1016/j.hydromet.2015.09.028, Vol.158, 83-93, 2015.12.
219. Kojo Twum-Knadu, Sasaki Keiko, Grace OFORI-SARPONG, Kwadwo Osseo-Asare, Takashi Kaneta, Activated carbon as surrogate for carbonaceous matter in gold ores: Degradation via enzyme treatment, Journal of the African Materials Research Society, in press, 2015.12.
220. Mutia Dewi Yuniati, Keitaro Kitagawa, Tsuyoshi Hirajima, Hajime Miki, Naoko Okibe, Keiko Sasaki, Suppression of pyrite oxidation in acid mine drainage by carrier microencapsulation using liquid product of hydrothermal treatment of low-rank coal, and electrochemical behavior of resultant encapsulating coatings, Hydrometallurgy, 10.1016/j.hydromet.2015.09.028, 158, 83-93, 2015.12, Pyrite is a mineral sulfide found extensively in acid mine drainage; this is one of the most serious environmental problems in the mining industry. Suppression of pyrite oxidation via carrier microencapsulation (CME) with silicon (Si) and organic carriers has been proposed. In the present study, use of the hydrothermal treatment liquid (HTL) produced from low-rank coal as a carrier in CME was investigated. In dissolution tests for 51 days with pyrite and iron-oxidizing bacteria, treatment with a mixture of HTL and a silicon reagent (Si-HTL) lowered the ferric ion concentration and limited bacterial attachment compared with untreated pyrite. This might be caused by catechol present in the HTL. A mixture of catechol and a silicon reagent (Si-Cat) was also used, and the coatings obtained using Si-HTL and Si-Cat were compared. The electrochemical behavior of the treated pyrite samples showed oxidative decomposition of the Si-Cat complex and formation of an encapsulating layer at 690 mV for Si-HTL and 550 mV for Si-Cat. The two semi-circular curves in the Nyquist plot simulations showed that the total impedances of the treated pyrite samples increased. Microscopic observations showed that the oxidative layer was silica rich. These data indicate that a silica-quinone coating is created and the pyrite oxidation rate can be suppressed by pretreatment with either Si-HTL or Si-Cat for 1 h..
221. Xinhong Qiu, Sasaki Keiko, Removal mechanism of polymeric borate by calcined layered double hydroxides containing different divalent metals, Colloids and Surfaces A: Physicochemical and Engineering Aspects, https://doi.org/10.1016/j.colsurfa.2015.07.036, Vol.482, 702-709, 2015.10.
222. Kenta Toshiyuki, Shugo Nagato, Tsuyoshi Hirajima, Sasaki Keiko, Takuro Naruse, Takeshi Kawashima, Influence of Mg components in hydroxylated calcined dolomite to (co-)precipitation of fluoride with apatites, Chem. Engng. J., 10.1016/j.cej.2015.10.029, 285, 487-496, 2015.10.
223. Widi Astuti, Tsuyoshi Hirajima, Sasaki Keiko, Naoko Okibe, Comparison of effectiveness of citric acid and other acids in leaching of different Indonesian low-grade saprolitic ores, Minerals Engineering,, doi:10.1016/j.mineng.2015.10.001, 85, 1-16, 2015.10.
224. Keiko Sasaki, Koichiro Takatsugi, Tsuyoshi Hirajima, Erratum
Effects of initial Fe2 + concentration and pulp density on the bioleaching of Cu from enargite by Acidianus brierleyi (Hydrometallurgy (2011) 109:1-2 (153-160) (DOI:10.1016/j.hydromet.2011.06.008)), Hydrometallurgy, 10.1016/j.hydromet.2015.08.013, 157, 2015.10.
225. Mari YOSHIDA, Paulmanickam KOILRAJ, Xinhong QIU, Tsuyoshi HIRAJIMA, Keiko SASAKI, Sorption of arsenate on MgAl and MgFe layered double hydroxides derived from calcined dolomite, Journal of Environmental Chemical Engineering, https://doi.org/10.1016/j.jece.2015.05.016, Vol.3, Issue 3, 1614-1621, 2015.09.
226. Wuhui Luo, Keiko Sasaki, Tsuyoshi Hirajima, Surfactant-modified montmorillonite by benzyloctadecyldimethylammonium chloride for removal of perchlorate, Colloids and Surfaces A: Physicochemical and Engineering Aspects, https://doi.org/10.1016/j.colsurfa.2015.06.025, 481, 616-625, 2015.09.
227. Liu Xiangchun, Tsuyoshi Hirajima, Sasaki Keiko, Investigation of the Changes in Hydrogen Bonds During Low-Temperature Pyrolysis of Lignite by Diffuse Reflectance FT-IR Combined with Forms of Water, Industrial & Engineering Chemistry Research, in press, 2015.09.
228. Wuhui Luo, Keiko Sasaki, Tsuyoshi Hirajima, Effect of surfactant molecular structure on perchlorate removal by various organo-montmorillonites, Applied Clay Science, 10.1016/j.clay.2015.06.003, 114, 212-220, 2015.09, A series of organo-montmorillonites (organo-Mt) was synthesized using various cationic surfactants with different alkyl-chain lengths, head groups, and alkyl-chain numbers, which were systematically examined for perchlorate adsorption. The products were characterized by the specific surface area, field-emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. In addition, the surfactant loadings and surface charges were investigated by CHN analysis and zeta potential measurements. The greatest adsorption capacity of 0.95. mmol/g-composite was obtained on benzyloctadecyldimethylammonium-modified Mt. Increasing the alkyl-chain length significantly enhanced the capacity and selectivity for perchlorate adsorption, but resulted in decrease of adsorption rate. Compared with trimethylammonium and pyridinium with the same alkyl-chain length, the benzyldimethylammonium as a head group showed better performance in terms of adsorption capacity and selectivity of perchlorate because of higher hydrophobicity. Moreover, increasing the alkyl-chain number decreased adsorption rate, but enhanced adsorption capacity, because of dense packing of alkyl chains and high driving force for entrapment of counter ion-accompanying surfactant. The perchlorate adsorption performance of organo-Mt was synergistically influenced by the alkyl-chain length, head group and alkyl-chain number of the surfactants used for modification..
229. Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki, Investigation of the Changes in Hydrogen Bonds during Low-Temperature Pyrolysis of Lignite by Diffuse Reflectance FT-IR Combined with Forms of Water, Industrial and Engineering Chemistry Research, 10.1021/acs.iecr.5b02474, 54, 36, 8971-8978, 2015.09, The changes in the hydrogen bonds (HBs) of Loy Yang lignite during low-temperature pyrolysis were investigated. The water content of all of the samples was determined by weighing the samples before and after heating in an oven. The changes in the number of the different types of HBs were determined using diffuse reflectance Fourier transform infrared spectroscopy considering the forms of water in lignite. The number of absorption bands, their peak positions, and the area of each peak in each spectrum were determined by curve-fitting analysis with the mixed Gaussian and Lorentzian function. The quantified integrated area of aromatic hydrogen atoms was used to accurately investigate the changes in the HBs. The results showed that the freezable and nonfreezable water contents of the total water weight in raw lignite were 84.8% and 15.2%, respectively. At low temperatures (T ≤ 100 °C), the main removed water was freezable water. The number of OH-lignite interactions decreased compared with raw lignite, which can be attributed to the breaking of bound-water-cluster-lignite HBs. The removal of free water induced a decrease in the number of OH-OH interactions, and then the transition of free water to bound water increased the number of OH-OH interactions. At medium temperatures (100 < T ≤ 200 °C), bound and nonfreezable water were mainly removed. The number of OH-lignite and OH-OH interactions changed because of the competition between the transition of bound water to nonfreezable water and desorption of bound and nonfreezable water. At higher temperatures (200 < T ≤ 250 °C), nonfreezable water was the main form of water removed, and carboxyl groups started to drastically pyrolyze. OH-lignite interactions changed as a result of the removal of nonfreezable water and the pyrolysis of carboxyl groups..
230. Wuhui Luo, Keiko Sasaki, Tsuyoshi Hirajima, Surfactant-modified montmorillonite by benzyloctadecyldimethylammonium chloride for removal of perchlorate, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2015.06.025, 481, 616-625, 2015.09, A high adsorption capacity (0.90mmol/g) of perchlorate was achieved on organo-montmorillonites (organo-MMTs) through modification by benzyloctadecyldimethylammonium chloride (BODMA-Cl), which typically possesses a long alkyl chain and a benzene ring. With increase in the amount of BODMA-Cl added, the XRD and FTIR results showed that the BODMA+/BODMA-Cl achieved a lateral bilayer, pseudo-trilayer and tilted paraffin-like bilayer configurations in the MMT interlayer space with improvement of ordered arrangement, and the formation of bilayers and/or micelles on the external surface also was demonstrated by TG-DTA and zeta potential curves. The EDX spectra of resultant products and adsorption isotherms of perchlorate on organo-MMTs suggested that a larger content of BODMA-Cl resulted in synthesized adsorbent with a greater adsorption capacity, because neutral BODMA-Cl is predominantly responsible for ion exchange with perchlorate. The maximum adsorption capacity was attained not only by enhanced affinity between BODMA+ and metallic layer of MMT, but also by increasing density of intercalated BODMA-Cl which is caused by hydrophobic interactions through long alkyl chains and π-π interactions through benzene rings among BODMA+/BODMA-Cl. It was also emphasized that the high adsorption capacity of perchlorate on organo-MMTs was achieved with a rapid adsorption rate and stably maintained against variations in temperature, initial solution pH and co-existing competitive anion..
231. Widi ASTUTI, Tsuyoshi Hirajima, Sasaki Keiko, Naoko Okibe, Kinetics of Nickel Extraction from Indonesian Saprolitic Ores by Citric Acid Leaching under Atmospheric Pressure, Minerals & Metallurgical Processing Journal, Vol.32, No.3, in press, 2015.08.
232. Mutia Dewi YUNIATI, Tsuyoshi Hiraji, Hajime Miki, Sasaki Keiko, Silicate Covering Layer on Pyrite Surface in the Presence of Silicon-Catechol Complex for Acid Mine Drainage Prevention, Materials Transactions, https://doi.org/10.2320/matertrans.M-M2015821, Vol.56, Issue 10, 1733-1741, 2015.08.
233. Sayo Moriyama, Sasaki Keiko, Tsuyoshi Hirajima, Sorption properties of boron on Mg–Al bimetallic oxides calcined at different temperatures, Separation and Purification Technology, 152, 192-199, 2015.08.
234. W. Astuti, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe, Kinetics of nickel extraction from Indonesian saprolitic ore by citric acid leaching under atmospheric pressure, Minerals and Metallurgical Processing, 32, 3, 176-185, 2015.08, The kinetics of leaching of a saprolitic ore from Indonesia by citric acid solution under atmospheric pressure was investigated. An examination of the effects of leaching temperature, citric acid concentration, pulp density and ore particle size on the dissolution rate of nickel found that they all had significant influence on the rate. The highest nickel recovery (95.6 percent) was achieved under the leaching conditions of ore particle size of 212-355 microns, citric acid concentration of 1 M, leaching time of 15 days, pulp density of 20 weight/volume percent, leaching temperature of 40°C and shaker speed of 200 rpm. The shrinking core model was found to be appropriate for describing the leaching kinetics of this ore in citric acid solutions at atmospheric pressure. The experimental data were well interpreted by this model with rate of reaction controlled by diffusion through the solid product layer. Using the Arrhenius expression, the apparent activation energy for nickel dissolution was evaluated as 12.38 kJ/mol. Finally, on the basis of the shrinking core model, a proposed empirical kinetic model for the leaching of nickel from this Indonesian saprolitic ore was expressed as a mathematical model, which was verified as consistent with the observed experimental results..
235. Sayo Moriyama, Keiko Sasaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki, Sorption properties of boron on Mg-Al bimetallic oxides calcined at different temperatures, Separation and Purification Technology, 10.1016/j.seppur.2015.08.023, 152, 192-199, 2015.08, Mg-Al bimetallic oxides produced via the calcination of hydrotalcite-like compounds ([(Mg0.75Al0.25(OH)2](An-)0.75/n·mH2O, where A is an anionic species) exhibited high potential for the removal of boron from aqueous solutions. X-ray diffraction patterns for the produced bimetallic oxides revealed that MgO was the primary phase within the range of investigated calcination temperatures. In addition, 11B NMR spectral analyses indicated that the Mg-Al bimetallic oxides captured trigonal B ([3]B) and tetrahedral B ([4]B) after the sorption of boron, regenerating hydrotalcite-like compounds. As the initial concentration of boron increased, the percentage of tetrahedral [4]B in solid residues after the sorption of boron increased. The [4]B/[3]B ratios in the solid residues increased with time along with the regeneration of hydrotalcite-like compounds. Furthermore, the Mg-Al bimetallic oxides produced from hydrotalcite-like compounds were more favorable than other bimetallic oxides and effective than single-phase MgO produced from MgCO3 at the same temperature, indicating that Mg-Al bimetallic oxides are stable materials with the potential for use in the remediation of contaminated sites and water..
236. Wuhui Luo, Sasaki Keiko, Tsuyoshi Hirajima, Effect of surfactant molecular structure on perchlorate removal by various surfactant-modified montmorillonites, Applied Clay Science, 114, 212-220, 2015.06.
237. Mari Yoshida, Paulmanickam Koilraj, Xinhong Qiu, Tsuyoshi Hirajima, Keiko Sasaki, Sorption of arsenate on MgAl and MgFe layered double hydroxides derived from calcined dolomite, Journal of Environmental Chemical Engineering, 10.1016/j.jece.2015.05.016, 3, 3, 1614-1621, 2015.06, Layered double hydroxides (LDHs) have the property to remove different anions due to their high anion exchange ability. Synthesis of LDHs using natural earth resources is highly desired in environmental concern. Single phases of Mg2.3Al-, Mg2.9Al- and Mg4Fe-LDHs were successfully synthesized from calcined dolomite (CaO·MgO) as Mg source as well as precipitant through optimization of microwave-assisted hydrothermal aging. Sorption data of arsenate over these LDHs were well fitted to non-linear Langmuir adsorption isotherm. Among the materials studied Mg2.3Al-LDH showed not only superior arsenate sorption capacity but also superior coverage of arsenate. This suggests there are some additional factors other than charge density to influence the sorption density. Mechanism of arsenate sorption was probed by different characterization techniques of solid residues after sorption such as X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transformed infrared, extended X-ray absorption fine structure analysis. Sorption of arsenate over MgAl-LDHs mediated through ion-exchange as well as surface adsorption, depending on charge density of metallic layers. However, sorption of arsenate over MgFe-LDH occurred through ion-exchange along with the formation of inner surface complexes, which leads disturbed layer stacking..
238. Moriyasu NONAKA, Tsuyoshi HIRAJIMA, Satoshi KUMAGAI,Keiko SASAKI, Hydrothermal Treatment of Lignite for CO2 Gasification, Journal of MMIJ, Vol.131, No.5, 219-225, 2015.05.
239. Xinhong Qiu, Keiko Sasaki, Kwadwo Osseo-Asare, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki, Sorption of H3BO3/B(OH)4 - on calcined LDHs including different divalent metals, Journal of Colloid And Interface Science, 10.1016/j.jcis.2014.12.093, 445, 183-194, 2015.05, LDHs with different divalent metals (Zn-LDH, Mg-LDH and Ca-LDH) have been synthesized and produced calcined LDHs (Zn-CLDH, Mg-CLDH and Ca-CLDH) for borate removal. Based on XRD, SEM, BET, 27Al NMR, CO2-TPD, and 11B NMR, detailed characterization of different CLDHs before and after reaction with the boron species was systematically performed. The surface area, basicity and the particle charge of the different CLDHs, which are related to the hydration and regeneration, were markably influenced by the nature of the divalent metals. Transformation of crystal phases and the types of boron species adsorbed by the different CLDHs varied as time changed. The regeneration of Ca-CLDH required the shortest time. However, Ca-LDH decomposed to release Ca2+ ions, forming ettringite with borate. Zn-CLDH also rapidly transformed into Zn-LDH. During this reconstruction, B(OH)4 - was intercalated into the interlayer of Zn-LDHs, which is the predominant mechanism of borate removal by Zn-CLDH. Increase in the initial pH caused a competition between borate and OH- so that the removal efficiency of borate by Zn-CLDH decreased. For Mg-CLDH, surface complexation and electrostatic attraction were included in the first stage, immobilizing boric acid into Mg(OH)2 and attracting borate as interlayer anionic species into the new forming Mg-LDHs in the second stage..
240. Naoko Okibe, Kiyomasa Sueishi, Mikoto Koga, Yusei Masaki, Tsuyoshi Hirajima, Sasaki Keiko, Selenium (Se) Removal from Copper Refinery Wastewater Using a Combination of Zero-Valent Iron (ZVI) and Se(VI)-Reducing Bacterium,Thauera selenatis, Materials Transactions, 2015.04.
241. Xinhong Qiu, Sasaki Keiko, Yu Takaki, Tsuyoshi Hirajima, Keiko IDETA, Jin Miyawaki, Mechanism of boron uptake by hydrocalumite calcined at different temperatures, Journal of Hazardous Materials, 10.1016/j.jhazmat.2015.01.066, Vol.287, 268-277, 2015.04.
242. Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Anggoro T Mursito, Sasaki Keiko, Use of FT-IR combined with forms of water to study of the changes in hydrogen bonds during low-temperature heating of lignite, Drying Technology, in press, 2015.03.
243. Paulmanickam KOILRAJ, Kannan Srinivasan, Keiko SASAKI, Amino Acid Assisted Solvothermal Synthesis of Layered Double Hydroxides, Fourth International Conference on Multifunctional, Hybrid and Nanomaterials, P1.038, 2015.03.
244. Yusei Masaki, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe, Bioreduction and Immobilization of Hexavalent Chromium by the Extremely Acidophilic Fe(III)‑reducing Bacterium Acidocella aromatica Strain PFBC, Extremophiles, doi: 10.1007/s00792-015-0733-6, Vol.19, Issue 2, pp.495-503, 2015.03.
245. Wuhui LUO, Keiko SASAKI, Tsuyoshi HIRAJIMA, Evaluation of BDTAC, DDAC and BDOAC-modified Montmorillonites for Perchlorate Removal, Fourth International Conference on Multifunctional, Hybrid and Nanomaterials, P1.247, 2015.03.
246. Xinhong QIU, Keiko SASAKI, Synthesis of Layered Double Hydroxide Intercalated with Gluconate for Removal of Boron Species, Fourth International Conference on Multifunctional, Hybrid and Nanomaterials, 2015.03.
247. Xinhong Qiu, Sasaki Keiko, Kwadwo Osseo-Asare, Tsuyoshi Hirajima, Keiko IDETA, Jin Miyawaki, Sorption of H3BO3/B(OH)4- on calcined LDHs including different divalent metals , Journal of Colloid and Interface Science, 445, 183-194, 2015.01.
248. Xinhong Qiu, Mari Yoshida, Tsuyoshi Hirajima, Sasaki Keiko, Rapid synthesis of LDHs by using dolomite as a magnesium source and its application in borate removal , Materials Transactions, 2015.01.
249. Masahito Tanaka, Yuta Yamaji, Yuken Fukano, Kazuhiko Shimada, Junichiro Ishibashi, Tsuyoshi Hirajima, Keiko Sasaki, Mitsuru Sawada, Naoko Okibe, Biooxidation of Gold-, Silver, and Antimony-Bearing Highly Refractory Polymetallic Sulfide Concentrates, and its Comparison with Abiotic Pretreatment Techniques, Geomicrobiology Journal, 10.1080/01490451.2014.981645, 32, 6, 538-548, 2015.01, Effectiveness of different pure and mixed cultures of three moderately thermophilic, extremely acidophilic bacterial strains (Acidimicrobium ferrooxidans ICP, Sulfobacillus sibiricus N1, Acidithiobacillus caldus KU) were investigated for biooxidation of highly refractory polymetallic gold ore concentrates. Despite of its complex mineralogy and the presence of a mixture of potentially inhibitory metals and metalloids, the concentrate was readily dissolved in defined mixed cultures including both iron and sulfur oxidizers, releasing as much as 80% of soluble Fe and 61% of soluble As. Factors to affect microbial mineral dissolution efficiencies (i.e. microbial As(III) oxidation ability, formation of secondary mineral precipitation (e.g. jarosite, elemental sulfur, scorodite, anglesite), and microbial population dynamics during biooxidation) were studied, based on which roles of individual microbes and their synergistic interactions during biooxidation were discussed. Applying the biooxidation pretreatment using the most efficient mixed cultures containing all three strains significantly improved the recovery of both Au (from 1.1% to 86%) and Ag (from 3.2% to 87%). Finally, this study provides one of the very few available comparisons of the effectiveness of different pretreatment techniques for refractory gold ore concentrates: Compared with other abiotic pretreatment approaches (roasting, pressure oxidation, and alkali dissolution), biooxidation was shown to be one of the most effective options in terms of the recovery of Au and Ag..
250. Yusei Masaki, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe, Bioreduction and immobilization of hexavalent chromium by the extremely acidophilic Fe(III)-reducing bacterium Acidocella aromatica strain PFBC, Extremophiles, 10.1007/s00792-015-0733-6, 19, 2, 495-503, 2015.01, The extremely acidophilic, Fe(III)-reducing heterotrophic bacterium Acidocella aromatica strain PFBC was tested for its potential utility in bioreduction of highly toxic heavy metal, hexavalent chromium, Cr(VI). During its aerobic growth on fructose at pH 2.5, 20 µM Cr(VI) was readily reduced to Cr(III), achieving the final Cr(VI) concentration of 0.4 µM (0.02 mg/L), meeting the WHO drinking water guideline of 0.05 mg/L. Despite of the highly inhibitory effect of Cr(VI) on cell growth at higher concentrations, especially at low pH, Cr(VI) reduction activity was readily observed in growth-decoupled cell suspensions under micro-aerobic and anaerobic conditions. Strain PFBC was not capable of anaerobic growth via dissimilatory reduction of Cr(VI), such as reported for Fe(III). In the presence of both Cr(VI) and Fe(III) under micro-aerobic condition, microbial Fe(III) reduction occurred only upon complete disappearance of Cr(VI) by its reduction to Cr(III). Following Cr(VI) reduction, the resultant Cr(III), supposedly present in the form of cationic CrIII(OH2)6 3+, was partially immobilized on the negatively charged cell surface through biosorption. When Cr(III) was externally provided, rather than microbially produced, it was poorly immobilized on the cell surface. Cr(VI) reducing ability was reported for the first time in Acidocella sp. in this study, and its potential role in biogeochemical cycling of Cr, as well as its possible utility in Cr(VI) bioremediation, in highly acidic environments/solutions, were discussed..
251. Xinhong Qiu, Mari Yoshida, Tsuyoshi Hirajima, Keiko Sasaki, Rapid synthesis of LDHs using dolomite as a magnesium source and application to borate removal, Materials Transactions, 10.2320/matertrans.M-M2014844, 56, 2, 224-228, 2015.01, A rapid and efficient method based on microwave-assisted treatment has been developed for preparing layered double hydroxides (LDHs) using natural dolomite as a magnesium source. The aging temperature was 120°C and the total synthetic time was only within 6 h. The product was fully characterized by elemental composition, powdery X-ray diffraction, and scanning electron microscopy, to be highly pure hydrotalcite with a flaky shape. The synthesized adsorbent exhibited the sorption capacity of 1.34 mmol/kg which is comparable to boron-specific resin. Based on 11B MAS NMR and XRD results, the principal mechanism for borate immobilization on the LDHs is ion-exchange followed by transformation of polyborate into monoborate in a process of drying..
252. Qiu Xinhong, Keiko Sasaki, Removal mechanism of polymeric borate by calcined layered double hydroxides containing different divalent metals, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2015.07.036, 482, 702-709, 2015.01, The removal mechanism of polymeric borate by calcined layered double hydroxides is not clear. In this work, layered double hydroxides containing different divalent metals were synthesized and calcined to produce calcined layered double hydroxides (Zn-, Mg-, and Ca-CLDH). Then, Zn-, Mg-, and Ca-CLDH were applied to remove polymeric borate. Zn-CLDH showed better performance for the removal of borate than Ca-CLDH, and hardly any borate was removed by Mg-CLDH. Based on the characterization results, the detailed removal process of polymeric borate by different calcined layered double hydroxides is discussed. Because there is little H3BO3 that can act as a trigger, and ligand promoted dissolution of the complex H3BO3 and MgO is prevented. Therefore, Mg-CLDH could not transform to the layered structure to immobilize the borate. For the Zn-CLDH, Zn-CLDH transformed into Zn-LDH, and polymeric borate was absorbed into the interlayer of layered double hydroxides, which is the dominant mechanism of borate removal by Zn-CLDH. Reconstruction of the Ca-LDH from the Ca-CLDH was more rapid than the other calcined layered double hydroxides. However, formation of borate-containing ettringite was the main removal mechanism in the first stage. With increasing reaction time, the reaction between CO32- and Ca2+ released from ettringite, and the regeneration of Ca-LDH to form CaCO3 were the main reasons for borate removal in the second stage..
253. Naoko Okibe, Kiyomasa Sueishi, Mikoto Koga, Yusei Masaki, Tsuyoshi Hirajima, Keiko Sasaki, Shinichi Heguri, Satoshi Asano, Selenium (Se) removal from copper refinery wastewater using a combination of zero-valent iron (ZVI) and Se(VI)-reducing bacterium, thaurea selenatis, Materials Transactions, 10.2320/matertrans.M2014457, 56, 6, 889-894, 2015.01, The copper refinery process produces Se(VI)-bearing wastewater with a high content of Cl- and SO42- ions. To overcome the negative effect caused by Cl- and SO42- ions on Se(VI) reduction and its following removal, this study investigated the possible synergistic effect of the combination of Se(VI)-reducing bacterium, Thaurea (T.) selenatis and zero-valent iron (ZVI). In the presence of SO42- (200mM) and Cl-(300 mM), the following was observed: (i) ZVI alone was unable to remove Se both under strictly aerobic and micro-aerobic conditions. (ii) Se(VI) reduction by T. selenatis alone was severely inhibited under anaerobic conditions (and thus no microbial growth was observed). (iii) On the other hand, T. selenatis was capable of growth and Se(VI) reduction under micro-aerobic conditions. (iv) Combining T. selenatis and ZVI under micro-aerobic conditions showed a synergistic effect on Se(VI) reduction, readily facilitating Se removal. This synergistic effect was optimized by adjusting the pH to near neutral (optimal for T. selenatis growth), but by adjusting the temperature to 35°C (sub-optimal for T. selenatis growth): Se removal of 55% by T. selenatis alone, was significantly improved to 98% by combining T. selenatis and ZVI. The proposed key process to display the synergistic effect on Se removal under micro-aerobic conditions is as follows: (i) Using the remaining dissolved O2 (DO) during the first hours, T. selenatis can overcome the inhibitory effect of Cl- and SO42- by growing with more energy-gaining aerobic respiration, (ii) ZVI indirectly serves as a reducing agent to maintain low DO levels, consequently readily switching from aerobic to anaerobic Se(VI) respiration by T. selenatis. (iii) ZVI may also be acting directly for Se deposition by reducing microbially-produced intermediate Se(IV), which is more reactive than original Se(VI). The present findings could be used as a basis for developing an economically feasible and environmentally harmless bio-treatment technology for Se(VI) containing copper refinery wastewaters..
254. Mutia Dewi Yuniati, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Silicate covering layer on pyrite surface in the presence of siliconcatechol complex for acid mine drainage prevention, Materials Transactions, 10.2320/matertrans.M-M2015821, 56, 10, 1733-1741, 2015.01, In this paper, prevention of pyrite oxidation by carrier microencapsulation (CME) was investigated. A possible layer structure was suggested following analysis with electrochemical and surface analysis techniques. Electrochemical study of treated pyrite samples showed that treatment with siliconcatechol (Si-Cat) for 6 h at an initial pH of 9.5 gave the best barrier properties and suppression of the samples. Scanning electron microscopy with energy-dispersive X-ray, and Fourier transform infrared (FTIR) analyses confirmed the presence of a silicate layer on the surface of treated pyrite. X-ray photoelectron spectroscopy indicated that the coating layers on the treated pyrite samples consisted of a network of Fe-O-Si and Si-O-Si units bonded to the surface of pyrite. The Si-O-C asymmetric stretching mode was also observed in FTIR spectra. Detailed spectroscopic analyses confirmed the formation of a silicate polymer on a silicaquinone layer, which resulted in the effective suppression effect shown by Si-Cat-treated pyrite at increasing pH..
255. Keiko Sasaki, Spectroscopic study on the bioleaching of enargite using thermophile, Microbiology for Minerals, Metals, Materials and the Environment, 135-152, 2015.01, Enargite (Cu3AsS4) is a representative copper-arsenic sulphide mineral. It occurs locally in some ore deposits, especially epithermal high sulphidation deposits (Arribas, 1995) and porphyry copper systems (Lattanzi et al., 2008). Although enargite is also valuable as a copper resource, the arsenic in the mineral makes it environmentally toxic through emissions associated with smelting (Dutré and Vandecasteele, 1995)..
256. Keiko Sasaki, Qianqian Yu, Synthesis of a biotemplated lithium ion-sieve derived from fungally formed birnessite, Advances in the Environmental Biogeochemistry of Manganese Oxides, 10.1021/bk-2015-1197.ch009, 169-183, 2015.01, Biogenic birnessite is a stable form of manganese oxide found in nature that originates from microbial oxidation. Its unique structural properties provide potential for materials scientists to fabricate new functionalized materials. This study used a manganese-oxidizing fungus, Paraconiothyrium sp. WL-2, as a bio-oxidizer and biotemplate to prepare a lithium ion-sieve in the shape of a microtube through a solid-state transformation by calcination. The effect of calcination temperature was studied in terms of chemical composition, structure, and morphology. The results showed that the calcination temperature affects not only the weight fraction but also the crystallinity of the lithium manganese oxide spinel, which significantly influences the adsorption capacity of lithium ions..
257. Evaluation of Sorption Characteristics of Lithium Ions in Simulated Geothermal Waters on Bio-Templated Ion Sieve.
258. Hydrothermal Treatment of Lignite for CO2 Gasification.
259. Yuken FUKANO, Tsuyoshi HIRAJIMA, Keiko SASAKI, Naoko OKIBE, Arsenite Removal Using Acidophilic Fe(II)-Oxidizing Bacteria in the Presence of Carbon Fiber, International Symposium on Earth Science and Technology 2014 (CINEST), 350-351, Paper No. CINEST14-76, 2014.12.
260. Masahito TANAKA, Yuta YAMAJI, Yuken FUKANO, Tsuyoshi HIRAJIMA, Keiko SASAKI, Mitsuru SAWADA, Naoko OKIBE, Biooxidation of Alaskan Refractory Gold Ore Concentrates, International Symposium on Earth Science and Technology 2014 (CINEST), 225-226, Paper No. CINEST14-44, 2014.12.
261. Mari YOSHIDA, Xinhong QIU, Tsuyoshi HIRAJIMA, Keiko SASAKI, Comparison of Mg-Al and Mg-Fe Types of Ldhs Synthesized from Calcined Dolomite in Arsenate Sorption, International Symposium on Earth Science and Technology 2014 (CINEST), 119-121, Paper No. CINEST14-23, 2014.12.
262. Shiori MORISHITA, Tsuyoshi HIRAJIMA, Keiko SASAKI, Naoko OKIBE, Effect of Cu(II) on Microbial Scorodite Crystallization from As(III)-Containing Copper Refinery Waste-Waters, International Symposium on Earth Science and Technology 2014 (CINEST), 352-353, Paper No. CINEST14-77, 2014.12.
263. Widi ASTUTI, Tsuyoshi HIRAJIMA, Keiko SASAKI, Naoko OKIBE, Effect of Leaching Reagent on the Atmospheric Dissolution of Indonesian Saprolitic Ore, International Symposium on Earth Science and Technology 2014 (CINEST), 112-113, Paper No. CINEST14-21, 2014.12.
264. Hidekazu MATSUOKA, Tsuyoshi HIRAJIMA, Keiko SASAKI, Hajime MIKI, Mitsuru SAWADA, Electrochemical Treatment of Molybdenite and Chalcopyrite, International Symposium on Earth Science and Technology 2014 (CINEST), 320-321, Paper No. CINEST14-67, 2014.12.
265. Shugo NAGATO, Kenta TOSHIYUKI, Takeshi KAWASHIMA, Tsuyoshi HIRAJIMA, Keiko SASAKI, Enhancement in Precipitation Rate of Fluoroapatite by Mg2+ Additives: Advanced Utilization of Hydrate of Calcined Dolomite in Water Treatment, International Symposium on Earth Science and Technology 2014 (CINEST), 324-325, Paper No. CINEST14-69, 2014.12.
266. Daisuke NAKAYAMA, Tsuyoshi HIRAJIMA, Keiko SASAKI, Naoko OKIBE, Formation of Bio-Pd(0) Nanoparticles Using Fe(III)-Reducing, Extremely Acidophilic Bacteria, International Symposium on Earth Science and Technology 2014 (CINEST), 227-228, Paper No. CINEST14-45, 2014.12.
267. Kenta TOSHIYUKI, Keiko IDETA, Jin MIYAWAKI, Dabo Ismaila,Tsuyoshi HIRAJIMA, Keiko SASAKI, Mechanism of Boric Acid/Borate Removal in Co-Precipitation with Hydroxyapatite and Evaluation of Maximum Sorption Density, International Symposium on Earth Science and Technology 2014 (CINEST), 125-127, Paper No. CINEST14-25, 2014.12.
268. Yusei MASAKI, Katsutoshi TSUTSUMI, Tsuyoshi HIRAJIMA, Keiko SASAKI, Naoko OKIBE, Microbial Community Structure Analysis of Chinoike-Jigoku (Blood-Pond Hell) Hot Spring and Search for Useful Microorganisms Applicable to Bioremediation of Heavy Metals, International Symposium on Earth Science and Technology 2014 (CINEST), 222-224, Paper No. CINEST14-43, 2014.12.
269. Takahiro MATSUMOTO, Tsuyoshi HIRAJIMA, Keiko SASAKI, Naoko OKIBE, Microbial Synthesis of Platinum Nanoparticles Using Extremely Acidophilic Iron-Reducing Bacteria, International Symposium on Earth Science and Technology 2014 (CINEST), 354-355, Paper No. CINEST14-78, 2014.12.
270. Akihiro INOUE, Wuhui LUO, Tsuyoshi HIRAJIMA, Keiko SASAKI, Sequential Modification of Montmorillonite Using DDAC and BDOAC for Removal of Perchlorate: Effect of DDAC Dosage, International Symposium on Earth Science and Technology 2014 (CINEST), 326-328, Paper No. CINEST14-70, 2014.12.
271. Mutia Dewi YUNIATI, Tsuyoshi HIRAJIMA, Hajime MIKI, Keiko SASAKI, Silica Covering Layer on the Chalcopyrite Surface: Electrochemical Behaviors and Depression Effect on Copper-Molybdenum Flotation, International Symposium on Earth Science and Technology 2014 (CINEST), 108-111, Paper No. CINEST14-20, 2014.12.
272. Yu TAKAKI, Xinhong QIU, Tsuyoshi HIRAJIMA, Keiko SASAKI, Sorption Mechanism of Arsenate onto Tri-Metallic Hydrocalumite, International Symposium on Earth Science and Technology 2014 (CINEST), 122-124, Paper No. CINEST14-24, 2014.12.
273. Akinobu IGUCHI, Hajime MIKI, Tsuyoshi HIRAJIMA, Keiko SASAKI, Mitsuru SAWADA, The Effect of Solution Potential and Silver Ion Addition on Dissolution Rate of Enargite, International Symposium on Earth Science and Technology 2014 (CINEST), 322-323, Paper No. CINEST14-68, 2014.12.
274. Tsuyoshi Hirajima, Masanori Mori, Sasaki Keiko, Osamu Ichikawa, Hajime Miki, Mohsen Farahat, Mitsuru Sawada, Selective flotation of chalcopyrite and molybdenite with plasma pre-treatment, Minerals Engineering, doi.org/10.1016/j.mineng.2014.07.011, Vol.66-68, 102-111, 2014.11.
275. Masahito Tanaka, Yuta Yamaji, Yuken Fukano, Kazuhiko Shimada, Junichiro Ishibashi, Tsuyoshi Hirajima, Sasaki Keiko, Mitsuru Sawada, Naoko Okibe, Biooxidation of gold-, silver, and antimony-bearing highly refractory polymetallic sulfide concentrates, and its comparison with abiotic pre-treatment techniques, Geomicrobiology Journal, DOI:10.1080/01490451.2014.981645, 2014.11.
276. Sasaki Keiko, Qianqian Yu, Taichi Momoki, Takuya Kaseyama, Adsorption characteristics of Cs+ ions onto biogenic birnessite, Applied Clay Science, 10.1016/j.clay.2014.06.028, Vol.101, 2014.11.
277. Takeshi Tsuruta, Daishi UMENAI, Tomonobu HATANO, Tsuyoshi Hirajima, Sasaki Keiko, Screening Micro-organisms for Cadmium Absorption from Aqueous Solution and Cadmium Absorption Properties of Arthrobacter nicotianae., Bioscience, Biotechnology, and Biochemistry, doi.org/10.1080/09168451.2014.930321, Vol.78, Issue 10, 1791-1796, 2014.10.
278. Qianqian Yu, Sasaki Keiko, In situ X-ray diffraction investigation of the evolution of a nanocrystalline lithium-ion sieve from biogenic manganese oxide, Hydrometallurgy, 10.1016/j.hydromet.2014.07.002, Vol.150, 253-258, 2014.10.
279. Takehiko TSURUTA, Daishi UMENAI, Tomonobu HATANO, Tsuyoshi HIRAJIMA, Keiko SASAKI, Screening Micro-organisms for Cadmium Absorption from Aqueous Solution and Cadmium Absorption Properties of Arthrobacter nicotianae, Bioscience, Biotechnology, and Biochemistry, http://dx.doi.org/10.1080/09168451.2014.930321, Vol. 78, Issue 10, pp.1791-1796, 2014.10.
280. Tsuyoshi HIRAJIMA, Masanori MORI, Osamu ICHIKAWA, Keiko SASAKI, Hajime MIKI, Mitsuru SAWADA, Selective Flotation of Chalcopyrite and Molybdenite by Surface Oxidation, XXVII International Mineral Processing Congress (IMPC 2014), Chapter2-20, 202-212, 2014.10.
281. Himawan PETRUS, Tsuyoshi HIRAJIMA, Keiko SASAKI, Hideyuki OKAMOTO, Separation Mechanism of Tennantite and Chalcopyrite with Flotation after Oxidation Using Oxygen, XXVII International Mineral Processing Congress (IMPC 2014), Chapter 2-12, 119-131, 2014.10.
282. Hajime MIKI, Tsuyoshi HIRAJIMA, Mutia Dewi YUNIATI, Keiko SASAKI, Suppression of Pyrite and Arsenopyrite Oxidation by Silica Coating: Electrochemical Aspects and the Mechanism, XXVII International Mineral Processing Congress (IMPC 2014), Chapter12-12, 101-110, 2014.10.
283. Tomoyo Goto, Sasaki Keiko, Effect of trace elements in fish bones on crystal characteristics of hydroxyapatite obtained by calcination, Ceramics International, 10.1016/j.ceramint.2014.03.067, Vol.40, Issue 7, PartB, 10777-10785, 2014.08.
284. M.A. Halim, Ratan K. Majumder, G.Rasul, Yoshinari HIROSHIRO, Sasaki Keiko, J. Shimada, Kenji Jinno, Geochemical Evaluation of Arsenic and Manganese in Shallow Groundwater and Core Sediment in Singair Upazila, Central Bangladesh, Arabian Journal for Science and Engineering, Vol.39, Issue 7, 5585-5601, in press, 2014.07.
285. Naoko Okibe, Masahito Tanaka, Mitsuru Sawada, Keiko Sasaki, Tsuyoshi Hirajima, Biooxidation of Alaskan refractory gold ore concentrates, Biohydrometallurgy `14, 2014.06.
286. Hisaya TSUJI, Pilasinee LIMSUWAN, Tsuyoshi HIRAJIMA, Keiko SASAKI, Hajime MIKI, Satoshi KUMAGAI, Recovery of Furfural Produced by Hydrothermal Treatment with Biomass Charcoal, International Journal of Environment, Vol.4, No.1, pp.11-17, 2014.06.
287. Sorption Mechanism of Boron to Magnesium Hydroxide using Co-precipitation Process in Aqueous Solution.
288. Naoki Higashidani, Takashi Kaneta, Nobuyuki Takeyasu, Shoji Motomizu, Naoko Okibe, Sasaki Keiko, Speciation of arsenic in a thermoacidophilic iron-oxidizing archaeon, Acidianus brierleyi, and its culture medium by inductively coupled plasma-optical emission spectroscopy combined with flow injection pretreatment using an anion-exchange mini-column, Talanta, 122, 240-245, 2014.05.
289. Sasaki Keiko, Tomoyo Goto, Immobilization of Sr2+ on Naturally Derived Hydroxyapatite by Calcination of Different Species of Fish Bones and Influence of Calcination on Ion-exchange Efficiency, Ceramics International, 10.1016/j.ceramint.2014.03.169, Vol.40, Issue 8, Part A, 11649-11656, 2014.04.
290. Takehiko Tsuruta, Keiko Sasaki, Screening Microorganisms for Cadmium Absorption from Aqueous Solution and the Cadmium Absorption Properties of Arthrobacter nicotianae, Bioscience, Biotechnology, and Biochemistry, in press, 2014.04.
291. Masahito TANAKA, Mitsuru SAWADA, Keiko SASAKI, Tsuyoshi HIRAJIMA, Naoko OKIBE, Biooxidation of Refractory Gold Ore Concentrates Using Moderately Thermophilic, Acidophilic Bacteria, International Conference on Biological, Civil and Environmental Engineering (BCEE-2014), p.242, 2014.03.
292. Mari YOSHIDA, Xinhong QIU, Tsuyoshi HIRAJIMA, Keiko SASAKI, Synthesis of Layered Double Hydroxides Derived from Dolomite Using Microwaving Assisted Hydrothermal Treatment for Removal of Arsenate, International Conference on Biological, Civil and Environmental Engineering (BCEE-2014), p.245, 2014.03.
293. Osamu ICHIKAWA, Tsuyoshi HIRAJIMA, Masanori MORI, Keiko SASAKI, Hajime MIKI, Mitsuru SAWADA, XPS and AFM Analysis of Plasma Oxidized Chalcopyrite and Molybdenite for New Selective Flotation Technique, International Conference on Biological, Civil and Environmental Engineering (BCEE-2014), p.244, 2014.03.
294. Naoko Okibe, Masaharu Koga, Shiori Morishita, Masahito Tanaka, Shinichi HEGURI, Satoshi ASANO, Sasaki Keiko, Tsuyoshi Hirajima, Microbial formation of crystalline scorodite for treatment of As(III)-bearing copper refinery process solution using Acidianus brierleyi, Hydrometallurgy, 143, 34-41, 2014.03.
295. Keiko Sasaki, Xinhong Qiu, Jin Miyawaki, Keiko Ideta, Hitoshi Takamori, Sayo Moriyama, Tsuyoshi hirajima, Contribution of boron-specific resins containing N-methylglucamine groups to immobilization of borate/boric acid in a permeable reactive barrier comprising agglomerated MgO, Desalination, 10.1016/j.desal.2013.11.018, Vol.337, 17, 109-116, 2014.03.
296. Naoko Okibe, Masaharu Koga, Shiori Morishita, Masahito Tanaka, Shinichi Heguri, Satoshi Asano, Keiko Sasaki, Tsuyoshi Hirajima, Microbial formation of crystalline scorodite for treatment of As(III)-bearing copper refinery process solution using Acidianus brierleyi, Hydrometallurgy, 10.1016/j.hydromet.2014.01.008, 143, 34-41, 2014.03, Scorodite (FeAsO4·2H2O) is a thermodynamically stable mineral with advantages as an arsenic disposal compound. With an aim to immobilize highly toxic As(III) contained in the copper refinery process solution, eventually in the form of crystalline scorodite, the use of thermo-acidophilic iron-oxidizing archaeon, Acidianus brierleyi, was investigated. The extent of As(III) oxidation by Ac. brierleyi became greater at elevated culture As(III) concentrations, especially in the presence of yeast extract. Microbial growth on yeast extract was also implied to facilitate As(III) oxidation by Fe(III) on cell surface. When the initial Fe(II)/As(III) ratio was set at 1.4 in the presence of yeast extract, both ions were readily oxidized and 86-100% of As was precipitated as crystalline scorodite. The molar ratio of microbially-oxidized Fe(II) and As(III) was an important factor to determine the type of the secondary mineral formed. Phosphate concentration was another critical factor for scorodite biomineralization. Biogenic scorodite was crystallized with almond-shaped polyhedron habit of 1 μm in size. This study demonstrates the applicability of a one-step bioprocess which enables treatment of As(III)-bearing copper refinery process solution by producing biogenic crystalline scorodite..
297. Xinhong QIU, Keiko SASAKI, Tsuyoshi HIRAJIMA, Keiko IDETA, Jin MIYAWAKI, One-step Synthesis of Layered Double Hydroxide-intercalated Gluconate for Removal of Borate, Separation and Purification Technology, DOI: 10.1016/j.seppur.2013.12.031. ISSN: 1383-5866., Vol.123, pp.114–123, 2014.02.
298. Xinhong Qiu, Sasaki Keiko, Tsuyoshi Hirajima, Keiko IDETA, Jin Miyawaki, Sorption of borate onto layered double hydroxides assembled in filter papers through in situ hydrothermal crystallization, Applied Clay Science, Vol.88-89, 134-143, 2014.02.
299. Xinhong Qiu, Keiko Sasaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki, One-step synthesis of layered double hydroxide-intercalated gluconate for removal of borate, Separation and Purification Technology, 10.1016/j.seppur.2013.12.031, 123, 114-123, 2014.02, The sorption of borate by ion exchange using a traditional layered double hydroxide (LDH) is affected by external conditions such as coexisting anions. Hydrotalcite intercalated with d-gluconate (G-LDH) was synthesized through a one-step microwave-assisted treatment and characterized by XRD, TEM, FTIR, TG/DTA and two-dimensional 11B NMR. Several factors that influence sorption of borate were investigated: gluconate content in the LDH, G-LDH dosage, coexisting anions, initial pH of borate solution and sorption temperature. The synthesized adsorbent exhibited a greater borate sorption rate than the traditional hydrotalcite (NO3-LDH) or a boron-specific resin. The maximum sorption capacity was 1.27 mmol/g (obtained by fitting to the Langmuir model). The G-LDH sorption density increased with increasing initial borate concentration and adsorbent dosage. In the presence of 50 mM sulfate, sorption of borate by NO3-LDH significantly decreased and no obvious sorption could be observed, whereas the sorption of borate by G-LDH was maintained at ∼0.57 mmol/g. 11B NMR indicated that the sorption mechanism of borate by G-LDH is mainly through bischelate and monodentate types of complexation with borate. This mechanism is similar to that of CRB05, and fundamentally different from that of NO3-LDH..
300. Xinhong Qiu, Keiko Sasaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki, Sorption of borate onto layered double hydroxides assembled on filter paper through in situ hydrothermal crystallization, Applied Clay Science, 10.1016/j.clay.2013.12.003, 88-89, 134-143, 2014.02, Boric acid is known to be difficult to immobilize because it has a pKa of 9.23, which means it is present in a molecular form in most aqueous environments and can be changed in the structure and nature with the change of the environmental conditions. Layered double hydroxides (LDHs) are potential sorbents for borate. However, the drawbacks of using LDHs for borate removal are that they are affected by the presence of other anions and are difficult to separate from water. In the present work, novel composites of Mg-Al type of LDH, synthesized onto filter papers and then intercalated with gluconate (F-LDH-G) were prepared. LDH with interlayer of carbonate form was first immobilized onto the surface of filter paper (F-LDH-CO3) by in situ hydrothermal crystallization, and then ion-exchanged sequentially with chloride (F-LDH-Cl) followed by gluconate. The influence of the molar ratio of gluconate/LDH and reaction time on F-LDH-G synthesis was explored. Products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and nuclear magnetic resonance as well as measurements of borate sorption. The optimal molar ratio of gluconate/LDH and reaction time for preparing F-LDH-G from F-LDH-Cl were 40 and 24h (F-LDH-G-40-24h), respectively. F-LDH-G-40-24h had higher sorption density and greater stability than both the original filter paper and the filter papers containing other LDHs, even in the presence of other anions. 11B NMR and XRD results indicate that the principal mechanism for borate immobilization on F-LDH-G-40-24h is complexation of gluconate with borate in both bischelate and monodentate forms. The novel composite is boron-specific and facilitates solid/liquid separation..
301. Sayo MORIYAMA, Keiko SASAKI, Tsuyoshi HIRAJIMA, Effect of Calcination Temperature on Mg-Al Bimetallic Oxides as Sorbents for the Removal of F- in Aqueous Solutions, Chemosphere, 10.1016/j.chemosphere.2013.10.018, Vol.95, pp.597-603, 2014.01.
302. Sasaki Keiko, Sayo Moriyama, Effect of calcination temperature for magnesite on interaction of MgO-rich phases with boric acid, Ceramics International, 10.1016/j.ceramint.2013.07.056., Vol.40, Issue 1, PartB, 1651-1660, 2014.01.
303. Dewi.Agustina IRYANI, Satoshi KUMAGAI, Moriyasu NONAKA, Yoshinobu NAGASHIMA, Keiko SASAKI, Tuyoshi HIRAJIMA, The Hot Compressed Water Treatment of Solid Waste Material from the Sugar Industry for Valuable Chemical Production, International Journal of Green Energy, 10.1080/15435075.2013.777909, Vol.11, Issue 6, pp.577-588, 2014.01.
304. Keiko Sasaki, Sayo Moriyama, Effect of calcination temperature for magnesite on interaction of MgO-rich phases with boric acid, Ceramics International, 10.1016/j.ceramint.2013.07.056, 40, 1 PART B, 1651-1660, 2014.01, Magnesia (MgO), which can be obtained by calcination of natural magnesite, is one of the most effective known sorbents for borate in aqueous solutions. Here we examine the effect of calcination temperature on sorption of borate for MgO-rich phases produced by calcination of magnesite at 873-1373 K. Calcination at or above 1273 K produced a single magnesium oxide phase, whereas basic magnesium carbonates (mMgCO3·nMg(OH)2· xH2O) formed in association with magnesium oxide at or below 1073 K. Calcination temperature directly affected the efficiency of decarbonation of magnesium carbonate, and the solubility and basicity of magnesium oxide in the resultant calcined products. These factors (along with the boron concentration) essentially control the immobilization mechanism of borate on the calcined MgO-rich phases. After sorption of borate on products calcined at lower temperatures, different types of basic magnesium carbonates were formed that are less effective at immobilizing borate. At low borate concentrations, under saturation for magnesium borate hydrate (Mg7B4O 13·7H2O), co-precipitation of borate with Mg(OH)2 predominates. However, as magnesium borate hydrate becomes supersaturated, both precipitation of Mg7B4O 13·7H2O and co-precipitation with Mg(OH) 2 contribute significantly to borate immobilization. Calcination temperature is a key practical factor affecting the borate sorption efficiency by changing the immobilization mechanism..
305. M. A. Halim, Ratan K. Majumder, G. Rasul, Yoshinari Hiroshiro, Keiko Sasaki, J. Shimada, K. Jinno, Geochemical Evaluation of Arsenic and Manganese in Shallow Groundwater and Core Sediment in Singair Upazila, Central Bangladesh, Arabian Journal for Science and Engineering, 10.1007/s13369-014-1111-x, 39, 7, 5585-5601, 2014.01, Geochemical characteristics of shallow groundwaters and core sediments are studied to better understand the sources and transportation process responsible for As and Mn enrichment in Singair Upazila of Manikgonj District in Bangladesh. Results demonstrate that the groundwater is mostly of Ca-HCO3 and Ca-Mg-HCO3 types. Concentrations of As in groundwater ranged from 1 to 159 μg/L, with about 59% of these exceeded the WHO drinking water guideline of 10 mg/L. In addition, all groundwater samples had higher concentrations of Mn (0.6-5.7 mg/L) and Fe (0.9-16.5 mg/L) than the WHO drinking water guidelines (0.4 and 0.3 μg/L, respectively). Most groundwaters contained both As(III) and As(V) species in which the concentration of As(III) was generally higher than that of As(V). High concentration of As (23 mg/kg) with elevated levels of FeO, MnO and TOC were found within the upper 15 m of silty clay sediments. Multivariate geostatistical analysis showed that dissolution of the Fe-Mn oxides was the dominant process of As and Mn release in groundwater. Geochemical modeling suggested that the concentrations of As, Mn, Fe and PO4 3- in groundwaters were also influenced by secondary minerals phases in addition to redox processes..
306. Tsuyoshi Hirajima, Masanori Mori, Osamu Ichikawa, Keiko Sasaki, Hajime Miki, Mohsen Farahat, Mitsuru Sawada, Selective flotation of chalcopyrite and molybdenite with plasma pre-treatment, Minerals Engineering, 10.1016/j.mineng.2014.07.011, 66, 102-111, 2014.01, For pretreatment of selective flotation, plasma treatment of chalcopyrite and molybdenite was applied then the minerals were washed by solution at pH 9 with oxygen bubbling. Surface characteristics of these minerals were investigated with AFM, XPS, zeta potential and contact angle measurements. Contact angle of chalcopyrite and molybdenite decreased a lot by plasma treatment. When they were washed with pH 9 solution with oxygen bubbling, contact angle of molybdenite increased whereas chalcopyrite one kept low. Adhesion force measurements indicated similar behavior. Result of flotation experiments indicated low recovery of both chalcopyrite and molybdenite after plasma treatment and only molybdenite recovery became higher after washing. Selective flotation of chalcopyrite and molybdenite could be achieved with this process. However, flotation of mixture of chalcopyrite and molybdenite after these treatments indicated both chalcopyrite and molybdenite were depressed. Addition of emulsified kerosene changed the flotation results where molybdenite was floated and chalcopyrite was depressed. Possible mechanism of selective flotation was proposed from the results of XPS, AFM, etc..
307. Himawan T.B.M. Petrus, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki Okamoto, Separation mechanism of tennantite and chalcopyrite with flotation after oxidation using oxygen, 27th International Mineral Processing Congress, IMPC 2014 IMPC 2014 - 27th International Mineral Processing Congress, 2014.01, Flotation of arseno bearing minerals from their copper ore has been an interest due to the increasing awareness on protecting the environment by minimizing the possibility of exposed arsenic compound. Some approaches have been proposed, but the mechanisms of separations have not yet fully understood. In this study, oxidation using oxygen was applied. Instead of the complex copper ore flotation results, pure single mineral of tennantite and chalcopyrite foatability was conducted using Hallimond tube. Resembled with the flotation results of copper concentrate containing tennantite, the separation possessed the best result at alkaline condition (pH 11) at where the arsenic content was reduced from 3300 ppm to 1800 ppm. In order to be able to understand the mechanism of the separation atomic force microscope (AFM) was utilized. AFM images showed changes in morphology and behavior when minerals were treated in both acid and alkaline condition. It was found that the morphological change showed the reaction products representing the rate of reactivity of tennantite and chalcopyrite. From the measured force of adhesion, it can be observed that in alkaline condition the surface of both minerals is more hydrophilic than that in acidic condition possessing higher value. This is in accordance with the X-ray photoelectron spectroscopy (XPS) spectra in which hydroxide moieties occupied the mineral surface in alkaline condition while elemental sulfur is in acidic condition..
308. Naoki Higashidani, Takashi Kaneta, Nobuyuki Takeyasu, Shoji Motomizu, Naoko Okibe, Keiko Sasaki, Speciation of arsenic in a thermoacidophilic iron-oxidizing archaeon, Acidianus brierleyi, and its culture medium by inductively coupled plasma-optical emission spectroscopy combined with flow injection pretreatment using an anion-exchange mini-column, Talanta, 10.1016/j.talanta.2014.01.057, 122, 240-245, 2014.01, The thermoacidophilic iron-oxidizing archaeon Acidianus brierleyi is a microorganism that could be useful in the removal of inorganic As from wastewater, because it simultaneously oxidizes As(III) and Fe(II) to As(V) and Fe(III) in an acidic culture medium, resulting in the immobilization of As(V) as FeAsO4. To investigate the oxidation mechanism, speciation of the As species in both the cells and its culture media is an important issue. Here we describe the successive determination of As(III), As(V), and total As in A. brierleyi and its culture medium via a facile method based on inductively coupled plasma-optical emission spectroscopy (ICP-OES) with a flow injection pretreatment system using a mini-column packed with an anion-exchange resin. The flow-injection pretreatment system consisted of a syringe pump, a selection valve, and a switching valve, which were controlled by a personal computer. Sample solutions with the pH adjusted to 5 were flowed into the mini-column to retain the anionic As(V), whereas As(III) was introduced into ICP-OES with no adsorption on the mini-column due to its electrically neutral form. An acidic solution (1 M HNO3) was then flowed into the mini-column to elute As(V) followed by ICP-OES measurement. The same sample was also subjected to ICP-OES without being passed through the mini-column in order to determine the total amounts of As(III) and As(V). The method was verified by comparing the results of the total As with the sum of As(III) and As(V). The calibration curves showed good linearity with limits of detection of 158, 86, and 211 ppb for As(III), As(V), and total As, respectively. The method was successfully applicable to the determination of the As species contained in the pellets of A. brierleyi and their culture media. The results suggested that the oxidation of As(III) was influenced by the presence of Fe(II) in the culture medium, i.e., Fe(II) enhanced the oxidation of As(III) in A. brierleyi. In addition, we found that no soluble As species was contained in the cell pellets and more than 60% of the As(III) in the culture medium was oxidized by A. brierleyi after a 6-day incubation..
309. Takehiko Tsuruta, Daishi Umenai, Tomonobu Hatano, Tsuyoshi Hirajima, Keiko Sasaki, Screening micro-organisms for cadmium absorption from aqueous solution and cadmium absorption properties of Arthrobacter nicotianae, Bioscience, Biotechnology and Biochemistry, 10.1080/09168451.2014.930321, 78, 10, 1791-1796, 2014, To obtain basic information on how microbial cells absorb cadmium from aqueous solution, we examined cadmium absorption in various microorganisms. Of 51 micro-organism strains tested, we found that some Gram-positive bacteria, such as, Arthrobacter nicotianae and Bacillus subtilis, and some actinomycetes, such as, Streptomyces flavoviridis and S. levoris were highly capable of absorbing cadmium from an aqueous solution. A. nicotianae absorbed the largest amount of cadmium, over 800 μmol cadmium per gram of dry wt. cells. However, cadmium absorption by A. nicotianae was affected by the solution pH, cadmium concentration, and cell density. The absorption of cadmium was very rapid. Some factors that affected cadmium absorption by A. nicotianae cells were also discussed..
310. Tsuyoshi Hirajima, Masanori Mori, Osamu Ichikawa, Keiko Sasaki, Hajime Miki, Mitsuru Sawada, Selective flotation of chalcopyrite and molybdenite by surface oxidation, 27th International Mineral Processing Congress, IMPC 2014 IMPC 2014 - 27th International Mineral Processing Congress, 2014, For pretreatment of selective flotation, surface oxidation of chalcopyrite and molybdenite was applied by oxygen plasma then the minerals were washed by solution at pH 9 with oxygen bubbling. Surface characteristics of these minerals were investigated with AFM, XPS, zeta potential and contact angle measurements. Contact angle of chalcopyrite and molybdenite decreased a lot by plasma treatment. When they were washed with pH 9 solution with oxygen bubbling, contact angle of molybdenite increased whereas chalcopyrite one kept low. Adhesion force measurements indicated similar behavior. Result of flotation experiments indicated low recovery of both chalcopyrite and molybdenite after plasma treatment and only molybdenite recovery became higher after washing. Selective flotation of chalcopyrite and molybdenite could be achieved with this process. Possible mechanism of selective flotation was proposed from the results of XPS, AFM, etc..
311. Mutia Dewi YUNIATI, Tsuyoshi HIRAJIMA, Hajime MIKI, Keiko SASAKI, Electrochemical Study of Silicate Coating on Sulphide Minerals Oxidation Suppression, International Symposium on Earth Science and Technology 2013 (CINEST), pp.193-196, 2013.12.
312. Mari YOSHIDA, Xinhong QIU, Tsuyoshi HIRAJIMA, Keiko SASAKI, Synthesis of Layered Double Hydroxides Derived from Dolomite Using Microwaving Assisted Hydrothermal Treatment, International Symposium on Earth Science and Technology 2013 (CINEST), pp.238-241, 2013.12.
313. Taichi MOMOKI, Emiko MORIOKA, Qianqain YU, Keiko SASAKI, Tuyoshi HIRAJIMA, Application of Li+ Ion Sieve Derived from Biogenic Birnessite to Simulated Geothermal Waters: Selectivity of Li+ and Chemical Stability, International Symposium on Earth Science and Technology 2013 (CINEST), pp.400-403, 2013.12.
314. Masashi MAKI, Keiko SASAKI, Tsuyoshi HIRAJIMA, Naoko OKIBE, Biorecovery of Vanadium (V) Using Fe(III)-reducing, Acidophilic Bacterium, Acidocella aromatica Strain PFBC., International Symposium on Earth Science and Technology 2013 (CINEST), pp.384-387, 2013.12.
315. Masanori MORI, Tsuyoshi HIRAJIMA, Osamu ICHIKAWA, Keiko SASAKI, Hajime MIKI, Mitsuru SAWADA, Floatability Modification of Chalcopyrite and Molybdenite with Plasma Treatment, International Symposium on Earth Science and Technology 2013 (CINEST), pp.372-375, 2013.12.
316. Yusei MASAKI, Keiko SASAKI, Tsuyoshi HIRAJIMA, Naoko OKIBE, Fundamental Study on Cr(VI) Reduction by Acidophilic Fe(III)-reducing Bacterium, International Symposium on Earth Science and Technology 2013 (CINEST), pp.234-237, 2013.12.
317. Widi ASTUTI, Tsuyoshi HIRAJIMA, Keiko SASAKI, Naoko OKIBE, Leaching Behavior of Nickel from Indonesian Nickel Laterite Ores by Atmospheric Acid Leaching Using Citric Acid, International Symposium on Earth Science and Technology 2013 (CINEST), pp.202-205, 2013.12, .
318. Hajime MIKI, Tsuyoshi HIRAJIMA, Mutia Dewi YUNIATI, Keiko SASAKI, Study of Silicate Coating on Pyrite Oxidation Suppression: Fundamental Mechanism and Kinetic Analysis, International Symposium on Earth Science and Technology 2013 (CINEST), pp.189-192, 2013.12.
319. Osamu ICHIKAWA, Tsuyoshi HIRAJIMA, Masanori MORI, Keiko SASAKI, Hajime MIKI, Mitsuru SAWADA, Surfaces Characterization of Plasma Treated Chalcopyrite and Molybdenite, International Symposium on Earth Science and Technology 2013 (CINEST), pp.376-379, 2013.12.
320. Yu TAKAKI, Xinhong QIU, Tsuyoshi HIRAJIMA, Keiko SASAKI, Synthesis of Tri-metallic Layered Double Hydroxides for Immobilization of Arsenate, International Symposium on Earth Science and Technology 2013 (CINEST), pp.404-407, 2013.12.
321. M. A. Halim, R. K. Majumder, M. N. Zaman, S. Hossain, M. G. Rasul, Sasaki Keiko, Mobility and impact of trace metals in Barapukuria coal mining area, Northwest Bangladesh, Arabian Journal of Geoscience, DOI 10.1007/s12517-012-0769-1, Vol.6, Issue 12, 4593-4605, 2013.12.
322. M. A. Halim, R. K. Majumder, M. N. Zaman, S. Hossain, M. G. Rasul, Keiko Sasaki, Mobility and impact of trace metals in Barapukuria coal mining area, Northwest Bangladesh, Arabian Journal of Geosciences, 10.1007/s12517-012-0769-1, 6, 12, 4593-4605, 2013.12, Trace metals were analyzed in water and sediment samples from Barapukuria coal mine area of Bangladesh in order to evaluate their mobility and possible environment consequences. Cadmium is the most mobile element with an average partition coefficient (log Kd) of 2.95 L/kg, while V is the least mobile element with a mean log Kd of 5.50 L/kg, and their order of increasing mobility is: V < As < Pb < Fe < Cr < Se < Mn < Ni < Zn < Cu < Ba < Sr < Cd. Contents of organic carbon in sediment samples shows strong positive correlations with most trace metals as revealed by the multivariate geostatistical analysis. The overall variation in concentration is mainly attributed to the discharge of effluents originating from the coal mining activities around the study area. Compared to their background, Ni and Cu are the most enriched while significant enrichment of As, Mn, Ba, Sr, Cr, and Pb is also observed in the sediments. Geoaccumulation indices (Igeo) suggest sediments are moderately to heavily polluted with respect to Ni and Cu. The metal pollution index (MPI) varied from 91.91 to 212.01 and the highest value is found at site CM03 that is close to discharge point. The sediment quality guideline index (SQG-IIntervention) values (0.56-1.52) suggest that the sediments at the study area have moderate to high ecotoxicological risk..
323. Atsunori TAYAOKA, Eriko TAYAOKA, Tsuyoshi HIRAJIMA, Keiko SASAKI, Development of Image Processing System for Air Classification, Proceedings of the 12th International Symposium on East Asian Resources Recycling Technology (EARTH2013), pp.452-455, 2013.11.
324. Himawan Tri Bayu Murti PETRUS, Tuyoshi HIRAJIMA, Keiko SASAKI, Hideyuki OKAMOTO, Effect of Oxidation Time on the Floatability of Tennantite and Chalcopyrite; Surface Characterization Using X-Ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM), Flotation '13, Session 2, pp.1-14, 2013.11.
325. Tsuyoshi HIRAJIMA, Masanori MORI, Osamu ICHIKAWA, Keiko SASAKI, Hajime MIKI, Mitsuru SAWADA, Selective Flotation of Chalcopyrite and Molybdenite with Plasma Pre-treatment, Flotation '13, Session 4, pp.1-15, 2013.11.
326. Hajime MIKI, Tsuyoshi HIRAJIMA, Mutia Dewi YUNIATI, Keiko SASAKI, Suppression of Pyrite Oxidation by Silicate Coating with Catechol Complex Oxidation Kinetics Estimation with Electrochemistry, Proceedings of the 12th International Symposium on East Asian Resources Recycling Technology (EARTH2013), pp.601-604, 2013.11.
327. Qianqian Yu, Keiko Sasaki, Tsuyoshi Hirajima, Bio-templated synthesis of lithium manganese oxide microtubes and their application in Li+ recovery, Journal of Hazardous Materials, doi:10.1016/j.jhazmat.2013.08.027, Vol.262, 15, PP.38-47, 2013.11.
328. Qianqian Yu, Keiko Sasaki, Tsuyoshi Hirajima, Bio-templated synthesis of lithium manganese oxide microtubes and their application in Li+ recovery, Journal of Hazardous Materials, 10.1016/j.jhazmat.2013.08.027, 262, 38-47, 2013.11, Microbial transformations, a primary pathway for the Mn oxides formation in nature, provide potential for material-oriented researchers to fabricate new materials. Using Mn oxidizing fungus Paraconiothyrium sp. WL-2 as a bio-oxidizer as well as a bio-template, a special lithium ion sieve with microtube morphology was prepared through a solid-state transformation. Varying the calcination temperature from 300 to 700°C was found to influence sample properties and consequently, the adsorption of Li+. Lithium manganese oxide microtube (LMO-MTs) calcined at different temperatures as well as their delithiated products (HMO-MTs) were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Calcination temperatures affect not only the content but also the crystal structure of LMO spinel, which is important in Li+ adsorption. The optimized sample was obtained after calcination at 500°C for 4h, which shows higher Li+ adsorption capacity than particulate materials..
329. Qian Qian Yu, Emiko Morioka, Tsuyoshi Hirajima, Keiko Sasaki, Synthesis of biogenic Mn oxide and its application as lithium ion sieve, 20th International Biohydrometallurgy Symposium, IBS 2013 Integration of Scientific and Industrial Knowledge on Biohydrometallurgy, 10.4028/www.scientific.net/AMR.825.439, 439-442, 2013.11, Geomimetics, taking lessons from nature's biogenic mineralization mechanisms, can provide powerful tools for advancing biohydrometallurgical processing. Microbial transformations are largely responsible for the Mn oxides found in nature. In this research biogenic birnessite was produced by a manganese-oxidizing fungus, Paraconiothyrium sp. WL-2, at pH 6.5 under room temperature, and characterized by XRD and TG-DTA. Abiotic (chemically synthesized) acidic birnessite was also prepared hydrometallurgically and subjected to a similar battery of characterization techniques. Following thermal treatment the sorption characteristics of these two materials were compared. The biogenic precursor showed several advantages to produce more effective Li-ion sieve than the chemically synthesized precursor. First, a shorter calcination period was required to produce Li4Mn5O12 without other phases; second, a greater content and higher crystallinity of H4Mn5O12 were obtained from the biogenic precursor. These advantages might be caused by poorer crystallinity and around 20 wt% organic matter in biogenic birnessite. While sorption density of Li+ in mmol/g was basically dependent on contents of H4Mn5O12 phase, the unique morphologies and sorption density were maintained with biogenic precursor even after repetition of sorption/desorption of Li+..
330. Qianqian YU, Emiko MORIOKA, Tsuyoshi HIRAJIMA, Keiko SASAKI, Synthesis of Biogenic Mn Oxide and Its Application, 20th International Biohydrometallurgy Symposium 2013 (IBS-2013), p.197, 2013.10.
331. Keiko Sasaki, Synthesis of biogenic Mn oxide and its application as lithium ion sieve, Advanced Materials Research, 2013.10.
332. Sasaki Keiko, Mari Yoshida, Bashir Ahmmad Arima, Naoyuki Fukumoto, Tsuyoshi Hirajima, Sorption of fluoride on partially calcined dolomite, Colloids and Surfaces A: Physicochemical and Engineering Aspects, doi.org/10.1016/j.colsurfa.2012.11.039, Vol.435, 56-62, 2013.10.
333. Naoko Okibe, Masashi Maki, Keiko Sasaki, Tsuyoshi Hirajima, Mn(II)-oxidizing activity of pseudomonas sp. strain MM1 is involved in the formation of massive mn sediments around sambe hot springs in Japan, Materials Transactions, 10.2320/matertrans.M-M2013825, 54, 10, 2027-2031, 2013.10, There has been an increasing interest in the application of Mn(II) oxidizing microbes for Mn(II) containing waste water treatment, as well as biogenic Mn oxides for remediation of a number of toxic metals. Sambe hot spring in Shimane Prefecture, Japan is known for its Mn-rich spring water, and Mn oxide sediments are widely distributed over an area of 60m.
334. Qianqian Yu, Keiko Sasaki, Kazuya Tanaka, Toshihiko Ohnuki, Tsuyoshi Hirajima, Zinc Sorption During Bio-oxidation and Precipitation of Manganese Modifies the Layer Stacking of Biogenic Birnessite, Geomicrobiology Journal, 10.1080/01490451.2013.774075, 30, 9, 829-839, 2013.10, The formation and structural evolution of fungal mediate biogenic birnessite are dynamic processes. Although the associations of Zn with the pre-formed biogenic Mn oxides are relatively well understood, the reactivity of the intermediate precipitate at the initial stage of Mn bio-oxidation appears to differ from the final precipitate. In the present work, Zn sorption during precipitation of biogenic Mn oxides was investigated contrasting Zn sorption to pre-formed biogenic Mn oxides, using the Mn-oxidizing fungus Paraconiothyrium sp. WL-2. A substantially higher Zn uptake was found during precipitation of biogenic Mn oxides compared to Zn sorption to pre-formed biogenic Mn oxides. The presence of Zn during Mn oxidation resulted in a biogenic Mn oxide with reduced ordering in the c-axis. The precipitate was identified by X-ray diffraction (XRD) as a layer-type Mn oxide with structural properties similar to hexagonal birnessite. Extended X-ray absorption fine structure (EXAFS) spectroscopy showed that Zn forms triple-corner-sharing tetrahedral coordination (IVTCS-Zn) complexes on the surface of birnessite, which may inhibited layer stacking of birnessite in the final products. This study emphasizes the importance of the intermediate precipitates on Zn sorption, and provides insight regarding the dynamic interaction between Zn and Mn oxide in the process of microbiological oxidation. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file..
335. Keiko Sasaki, Mari Yoshida, Bashir Ahmmad, Naoyuki Fukumoto, Tsuyoshi Hirajima, Sorption of fluoride on partially calcined dolomite, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2012.11.039, 435, 56-62, 2013.10, Natural dolomite was calcined at different temperatures in the range 873-1373K and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption/desorption isotherm. The calcination temperature had considerable effect on the surface chemical composition, crystallinity, and basicity of CO2 gas sorption of each component in the calcined products. The sorption isotherm of both in low and high concentrations of fluoride (F-) was investigated for selected calcination products. The sample calcined at 973K was found to show the highest sorption density for F- at equilibrium concentrations lower than 0.5mM, which was equivalent to the maximum concentration limit of F-. In this range, the principle of F- removal is mainly based on destructive hydration of MgO. At equilibrium concentrations of F- higher than 0.5mM, the sorption process was controlled by precipitation of CaF2 and co-precipitation with Ca(OH)2 due to excess liberation of Ca2 ions from CaO. In this concentration region the products of calcination at higher temperatures are profitable for the immobilization of F-. Additionally, the effect of CO2 gas derived from carbonates on the reactivity of MgO to remove F- during calcination of natural dolomite was also discussed..
336. Qianqian YU, Emiko MORIOKA, Keiko SASAKI, Characterization of Lithium Ion Sieve Derived from Biogenic Mn Oxides, Microporous and Mesoporous Materials, http://dx.doi.org/10.1016/j.micromeso.2013.05.026, Vol.179, pp.122–127, 2013.09.
337. Naoko OKIBE, Masashi MAKI, Keiko SASAKI, Tsuyoshi HIRAJIMA, Mn(Ⅱ)-Oxidizing Activity of Pseudomonas sp. Strain MM1 is Involved in the Formation of Massive Mn Sediments around Sambe Hot Springs in Japan, Materials Transactions, Vol.54, No.10, pp.2027-2031, 2013.09.
338. Keiko Sasaki, Xinhong Qiu, Sayo Moriyama, Chiharu Tokoro, Keiko Ideta, Jin Miyawaki, Characteristic Sorption of H3BO3/B(OH) 4- on magnesium oxide, Materials Transactions, 10.2320/matertrans.M-M2013814, 54, 9, 1809-1817, 2013.09, The reaction mechanism of H3BO3/B(OH)4- with MgO in aqueous phase was investigated using sorption isotherm, XRD, 11B-NMR and FTIR. Release of Mg2+ was observed soon after contact of MgO with H3BO3 and maximum released Mg2+ was proportional to the initial boron concentration, suggesting ligand-promoted dissolution of MgO by H3BO3. The molecular form of H3BO3 was more reactive with MgO in releasing Mg2+ ions than B(OH)4 -. 11B-NMR results indicated that trigonal B ( [3]B) was predominant over tetrahedral B ([4]B) in solid residues after sorption of H3BO3. The molar ratio of [4]B/[3]B increased with H3BO3 sorption density. XRD patterns for the solid residues were assigned to Mg(OH)2 and peaks broadened with increasing H3BO 3 sorption density, except for (hk0) planes due to c-axis lattice strain induced by incorporation of H3BO3 between layers. These results indicated that H3BO3 interfered in the c-axis stacking of in Mg(OH)2. Molecular H3BO3 acted as a trigger when reacting with the MgO surface, releasing Mg2+ to produce an unstable complex leading to the precipitation formation of Mg(OH) 2, which is a sink for the immobilization of H3BO 3/B(OH)4-..
339. Hisaya TSUJI, Satoshi KUMAGAI, Pilasinee LIMSUWAN, Tsuyoshi HIRAJIMA, Keiko SASAKI, Hajime MIKI, Hydrothermal Treatment of Coconut Shell and Recovery of Furfural, International Conference on Green Energy and Technology, pp.172-175, 2013.08.
340. Naoko Okibe, Masashi Maki, Keiko Sasaki, Tsuyoshi Hirajima, Mn(II)-oxidizing activity of Pseudomonas sp. strain MM1 is involved in the formation of massive Mn sediments around Sambe hot springs in Japan, Materials Transactions, in press, 2013.08.
341. Keiko Sasaki, Xinhong Qiu, Hitoshi Takamori, Sayo Moriyama, Keiko Ideta, Jin Miyawaki, Immobilization of boron in groundwaters by combination of MgO with woodchips, Mineralogical Magazine, 77, 5, 2136, 2013.08.
342. Kazuya Tanaka, Qianqian Yu, Keiko Sasaki, Toshihiko Ohnuki, Cobalt(II) oxidation by biogenic Mn oxide produced by Pseudomonas sp. strain NGY-1, Geomicrobiology Journal, 10.1080/01490451.2013.791352, Vol.30, Issue 10, 874-885, 2013.08.
343. Sasaki Keiko, Qiu Xinhong, Sayo Mortiyama, Chiharu Tokoro, Keiko Ideta, Jin Miyawaki, Characteristic sorption of H3BO3/B(OH)4– on magnesium oxide, Materials Transactions, DOI: 10.2320/matertrans.M-M2013814, Vol.54, No.9, 1809-1817, 2013.08.
344. Sayaka IZAWA, Chiharu TOKORO, Shinya SUZUKI, Keiko SASAKI, Clarification for Boron Sorption Mechanism in Coprecipitation with Magnesium Hydroxide, Mineralogical Magazine, Vol.77, No.5, p.1367, 2013.07.
345. YU QIANQIAN, Keiko Sasaki, Kazuya TANAKA, Toshihiko OHNUKI, Tsuyoshi Hirajima, Zinc Sorption During Bio-oxidation and Precipitation of Manganese Modifies the Layer Stacking of Biogenic Birnessite, Geomicrobiology Journal, Vol.30, Issue 9, 829-839, 2013.07.
346. Naoko Okibe, Masaharu KOGA, Shinichi HEGURI, Satoshi ASANO, Keiko Sasaki, Tsuyoshi Hirajima, Simultaneous Oxidation and Immobilization of Arsenite from Refinery Waste Water by Thermoacidophilic Iron-oxidizing Archaeon, Acidianus brierleyi, Minerals Engineering, http://dx.doi.org/10.1016/j.mineng.2012.08.009, 48, 126-134, 2013.07.
347. Pilasinee Limsuwan, Satoshi Kumagai, Moriyasu Nonaka, Keiko Sasaki, Wiwut Tanthapanichakoon, Tsuyoshi Hirajima, Application of plasma treated activated carbon to enhancement of phenol removal by ozonation in three-phase fluidized bed reactor, 2013 3rd International Conference on Key Engineering Materials, ICKEM 2013 Key Engineering Materials III, 10.4028/www.scientific.net/AMR.701.305, 305-309, 2013.07, Plasma treatment of activated carbon (AC) was found to be an efficient method to enhance phenol removal by ozonation in a three-phase fluidized-bed reactor. The plasma treatment extended porous structure, changed surface morphologies, and produced oxygen functional groups on the surface of AC. Plasma-treated activated carbon together with O3 gave the best removal result, in which phenol was completely decomposed within 10 min (with pseudo first-order rate constant k = 0.286 min-1), while untreated AC without O3 showed the worst result (k = 0.024 min-1). Consequently, AC modified by plasma was shown to be a good material for removal of organic pollutants and yield superb performance in an integrated process with ozone in a fluidized-bed reactor..
348. Xinhong Qiu, Sasaki Keiko, Tsuyoshi Hirajima, Keiko IDETA, Jin Miyawaki, Temperature effect on the sorption of borate by a layered double hydroxide prepared using dolomite as a magnesium source, Chemical Engineering Journal, doi.org/10.1016/j.cej.2013.03.099, Vol.225, 664-672, 2013.06.
349. Xinhong Qiu, Keiko Sasaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki, Temperature effect on the sorption of borate by a layered double hydroxide prepared using dolomite as a magnesium source, Chemical Engineering Journal, 10.1016/j.cej.2013.03.099, 225, 664-672, 2013.06, A hydrotalcite-like compound prepared through chemical deposition using calcined dolomite as the magnesium source (D-LDH) was applied to remove borate. D-LDH calcined at different temperatures was characterized by specific surface area measurements, scanning electron microscope images, X-ray diffraction (XRD) patterns, and Fourier transform infrared (FTIR) spectra to optimize the calcination temperature and maximize the sorption capacity of borate. Greater sorption density of borate was observed at higher calcination temperature, and the sample calcined at 700°C showed the maximum sorption density. In addition, the sorption density of borate by D-LDH calcined at 700°C decreased with increasing initial pH. The solid residues after the sorption of borate were characterized by FTIR, 11B NMR (11Boron nuclear magnetic resonance), and XRD to explore the sorption mechanism of the calcined product at 700°C..
350. Keiko Sasaki, Xinhong Qiu, Yukiho Hosomomi, Sayo Moriyama, Tsuyoshi Hirajima, Effect of natural dolomite calcination temperature on sorption of borate onto calcined products, Microporous and Mesoporous Materials, 10.1016/j.micromeso.2012.12.029, Vol.171, 1-8, 2013.05.
351. Qianqain YU, Emiko Morioka, Sasaki Keiko, Synthesis of lithium ion sieve derived from biogenic Mn oxides, Microporous Mesoporous Materials, 10.1016/j.micromeso.2013.05.026, 179, 122-127, 2013.05.
352. Keiko Sasaki, Yoshitaka UEJIMA, Atsushi SAKAMOTO, Qianqian Yu, Junichiro Ishibashi, Naoko Okibe, Tsuyoshi Hirajima, Geochemical and Microbiological Analysis of Sambe hot springs, Shimane Prefecture, Japan, Resource Geology, DOI: 10.1111/rge.12002, Vol.63, Issue 2, 155-165, 2013.04.
353. Keiko Sasaki, Yoshitaka Uejima, Atsushi Sakamoto, Qianqian Yu, Junichiro Ishibashi, Naoko Okibe, Tsuyoshi Hirajima, Geochemical and Microbiological Analysis of Sambe Hot Springs, Shimane Prefecture, Japan, Resource Geology, 10.1111/rge.12002, 63, 2, 155-165, 2013.04, Microbiological contribution to the formation of the manganese deposits in Sambe hot springs, Shimane, was investigated in combination with water chemistry, characterization of sediments and microbial community structure. Analysis of bacterial and fungal community structure based on DNA extracted from a Mn-oxidizing enrichment culture indicated close matches with Pseudomonas putida, Phoma sp. and Plectosphaerella cucumerina, all Mn-oxidizing microorganisms. These sediments were poorly crystalline and formed at neutral pH values, which is characteristic of biogenic precipitates. The EPMA results demonstrated a positive correlation between Mn and Ba contents in well-crystalline Mn oxide grains. Substantial Ba contents were observed inside Mn oxide grains. These findings indicated that Ba contents in sediments are influenced by not only aqueous Ba2+ concentrations but also crystallinity of biogenic birnessite. Barium would be incorporated in birnessite during biomineralization..
354. Sayo Moriyama, Sasaki Keiko, Tsuyoshi Hirajima, Effect of calcination temperatures on Mg–Al bimetallic oxides as sorbents for the removal of F− in aqueous solutions, Chemosphere, doi.org/10.1016/j.chemosphere.2013.10.018, in press, 2013.03.
355. Xinhong Qiu, Sasaki Keiko, Tsuyoshi Hirajima, 宮脇 仁, 出田圭子, One-Step Synthesis of layer double hydroxide-intercalated gluconate for borate removal, Separation and Purification Technology, in press, 2013.03.
356. Moriyasu Nonaka, Tsuyoshi Hirajima, Keiko Sasaki, Gravity separation and its effect on CO2 gasification, Fuel, org/10.1016/j.fuel2011.10.074, Vol.103, 37-41, 2013.01.
357. Himawan Tri Bayu Murti PETRUS, Tsuyoshi Hirajima, Yuji OOSAKO, Moriyasu Nonaka, Keiko Sasaki, Takashi ANDO, Sustainable Recovery of Cenospheres from Coal Fly Ash Using Dry Separation Processes, Proceedings of The 5th AUN/SEED-Net Regional Conference on Materials Engineering & The 5th Regional Conference on Natural Resources and Materials , 94-95, 2013.01.
358. Tsuyoshi Hirajima, Himawan Tri Bayu Murti PETRUS, Keiko Sasaki, Hideyuki OKAMOTO, Selective Removal of Tennantite from Copper Concentrates, Proceedings of The 5th AUN/SEED-Net Regional Conference on Materials Engineering & The 5th Regional Conference on Natural Resources and Materials, 6-7, 2013.01.
359. Moriyasu Nonaka, Tsuyoshi Hirajima, Keiko Sasaki, Gravity separation and its effect on CO2 gasification, Fuel, 10.1016/j.fuel.2011.10.074, 103, 37-41, 2013.01, The CO2-blown integrated coal gasification combined cycle (IGCC) is a promising electric power generation technology that will reduce CO 2 emission, due to its high efficiency. Recent studies have found that base metals improve the coal char gasification in cases when they can interact with the char matrix at an atomic level. In this paper, we clarified the effect of heavy medium separation, which is one of the most popular coal cleaning technologies, on the CO2 char gasification. Before sink and float test and thermogravimetric analysis, Datong Coal from China was ground to below 20 mesh, which is a size usually used for a coal cleaning process. The float and sink test revealed that the highest separation efficiency would be obtained at a specific gravity of 1.45. The ash content would be reduced dramatically from 10.2% to ca. 4% and about 85% of combustibles would be recovered. The chars derived from different specific gravity fractions showed different gasification reactivity; the char from heavier fraction has gasification reactivity higher than the lighter fraction-derived char. This tendency agrees with the ash content; the heavier fraction has a higher ash content. Removal of ash from well-ordered holes in Fusinite and Semi-fusinite in Inertinite might increase the gasification reactivity..
360. Naoko Okibe, M. Koga, Keiko Sasaki, Tsuyoshi Hirajima, S. Heguri, S. Asano, Simultaneous oxidation and immobilization of arsenite from refinery waste water by thermoacidophilic iron-oxidizing archaeon, Acidianus brierleyi, Minerals Engineering, 10.1016/j.mineng.2012.08.009, 48, 126-134, 2013.01, The use of a thermophilic acidophilic iron-oxidizing archaeon, Acidianus brierleyi, was investigated for oxidation and immobilization of As(III) from acidic refinery waste water. Some As(III) oxidation was measured in all Ac. brierleyi cultures independently of the presence or concentration of Fe(II) in bulk solution; the exception was at initial Fe(II) concentration ([Fe(II)] ini) of 1000 mg l-1 where As(III) oxidation became markedly facilitated and consequently approximately 70% of As was immobilized as amorphous ferric arsenate. Providing 1000 mg l-1 Fe(III) instead of Fe(II) did not show the same effect, implying the importance of Fe(III) be microbially-produced and complexed in the archaeal EPS (extracellular polymeric substances) region for effective As(III) oxidation. The reaction towards secondary mineral formation shifted from ferric arsenate to jarosite at [Fe(II)]ini of >1000 mg l-1. Furthermore addition of jarosite seed crystals retarded the As(III) oxidation rate at [Fe(II)] ini of 1000 mg l-1. The observations indicate that by setting the appropriate bulk Fe(II)/As(III) ratio in Ac. brierleyi culture to achieve a certain concentration of Fe(III) within the EPS region, but at the same time to avoid jarosite formation, it is possible to maximize the As(III) oxidation rate and thus As immobilization efficiency. This study describes for the first time microbially-mediated simultaneous oxidation and immobilization of As(III) as ferric arsenate, using a thermoacidophilic iron-oxidizing archaeon, Ac. brierleyi..
361. Pilasinee LIMSUWAN, 熊谷 聡, Moriyasu Nonaka, Keiko Sasaki, Wiwut TANTHAPANICHAKOON, Tsuyoshi Hirajima, Application of Plasma Treated Activated Carbon to Enhancement of Phenol Removal by Ozonation in Three-Phase Fluidized Bed Reactor, Advanced Materials Research Journal , in press, 2012.12.
362. Dewi Agustina IRYANI, 熊谷 聡, Moriyasu Nonaka, Yoshinobu NAGASHIMA, Keiko Sasaki, Tsuyoshi Hirajima, Hot Compressed Water Treatment of Solid Waste Material from the Sugar Industry for Valuable Chemical Production, International Journal of Green Energy , DOI:10.1080/15435075.2013.777909, in press, 2012.12.
363. T. B.M. Himawan, Petrus, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki Okamoto, Alternative techniques to separate tennantite from chalcopyrite
Single minerals and arseno copper ore flotation study, 26th International Mineral Processing Congress, IMPC 2012: Innovative Processing for Sustainable Growth 26th International Mineral Processing Congress, IMPC 2012 Innovative Processing for Sustainable Growth - Conference Proceedings, 2038-2051, 2012.12, In this study, effect of thiosulphate and oxidation using oxygen were studied in arseno copper ore flotation. Single mineral study of chalcopyrite and tennantite in regard to the aforementioned techniques was also studied. Zeta potential, XPS, contact angle and floatability of single minerals were conducted for each treatment to understand the mechanism. It was revealed that the separation is best conducted in alkaline condition at where there will be interaction between thiosulphate and the mineral surface as well as the formation of hydroxide species in the oxidation using oxygen. From zeta potential of both thiosulphate and oxidation conditioning, it can be found that the reactivity of tennantite is much higher rather than chalcopyrite resulting higher rate of depression on both techniques as shown from contact angle and floatability of each mineral after treatment. XPS spectra confirmed qualitatively and quantitatively the existence of species responsible for the depression of each conditioning techniques. As for the copper ore flotation test, it is the oxidation using oxygen provides best performance after 60 minutes of oxidation..
364. Keiko Sasaki, Shoichi Tsuruyama, Sayo Moriyama, Stephanie Handley-Sidhu, Joanna C. Renshaw, Lynne E. Macaskie, Ion exchange capacity of Sr 2+ onto calcined biological hydroxyapatite and implications for use in permeable reactive barriers, Materials Transactions, 10.2320/matertrans.M-M2012813, 53, 7, 1267-1272, 2012.10, With the recent Fukushima incident, there is an urgent need to find cost effective and workable permeable reactive barrier (PRBs) for the remediation/retardation of problematic radionuclides. Catfish bones were calcined at various temperatures (4001100° C) to remove the organic matter (87.1 mgg 1) and to change the structural properties of the hydroxyapatite (HAP). Increasing temperatures increased the HAP crystallinity as indicated by a decrease in lattice strain (0.0098 to 0.00135) and an increase in crystallite sizes (5.0 × 10 8 to 7.7 × 10 8 m). There was also an observed decrease in specific surface areas (98.9 to 0.99m 2g 1) and increase in particle sizes (50 to 1000 nm). The sorption densities of Sr2+ decreased with increasing calcination temperatures, from 0.34 to 0.05 mmolg 1. However, once normalized for surface area, the sorption densities increased from 1.8 to 5.9 mmolm 2. Overall, this research has important implications for the design of hydroxyapatite PRBs with higher calcination temperatures producing a more reactive material with larger particle sizes for increased permeability. Lower calcination temperatures produced amorphous HAP material, which released more aqueous PO4 /3 3 and resulted in the precipitation of strontium phosphates, ultimately reducing the permeability of PRBs..
365. Keiko Sasaki, Koichiro Takatsugi, Olli H. Tuovinen, Spectroscopic analysis of the bioleaching of chalcopyrite by Acidithiobacillus caldus, Hydrometallurgy, 10.1016/j.hydromet.2012.07.013, 127-128, 116-120, 2012.10, The formation and consumption of elemental S were investigated in the bioleaching of chalcopyrite within and without a CE dialysis membrane in Acidithiobacillus caldus cultures. The bacteria were supplemented with tetrathionate outside the membrane. XPS analysis showed that monosulfide species and elemental S were formed on CuFeS 2 surface regardless of the enclosure in the dialysis membrane. They diminished over time in the inoculated systems. In the membrane enclosure, colloidal S partially dissolves and can pass the dialysis membrane for bacterial oxidation to sulfuric acid. Anaerobic pre-oxidation of CuFeS 2 by Fe 3 + produced S-rich deposition on mineral surface. The solubilization of Cu from membrane-enclosed pre-oxidized chalcopyrite in the A. caldus culture was much slower as compared to direct contact with bacteria. The difference is attributed to slow diffusion through the dialysis membrane as well as clogging caused by polymerized S on the inside of the membrane..
366. Sayo Moriyama, Keiko Sasaki, Tsuyoshi Hirajima, Effect of calcination temperatures in producing Mg–Al bimetallic oxides as sorbents for the removal of F− in aqueous solutions, Separation and Purification Technology, 2012.09.
367. Keiko Sasaki, Naoyuki FUKUMOTO, Sayo MORIYAMA, YU QIANQIAN, Tsuyoshi Hirajima, Chemical Regeneration of Magnesium Oxide Used as a Sorbent for Fluoride, Separation and Purification Technology, Vol.98, p.24-p.30, Vol.98. pp.24-30
, 2012.09.
368. Moriyasu Nonaka, Tsuyoshi Hirajima, 熊谷 聡, Keiko Sasaki, Upgrading and Drying of Lignite by Super- and Sub- Critical Fluids, International Symposium on Earth Science and Technology 2012 (CINEST2012), p.41-p.44, pp.41-44, 2012.09.
369. Dewi Agustina IRYANI, 熊谷 聡, Moriyasu Nonaka, Keiko Sasaki, Tsuyoshi Hirajima, Production of 5-hydroxymethyl Furfural from Sugarcane Bagasse Under Hot Compressed Water, Procedia Earth and Planetary Science, http://dx.doi.org/10.1016/j.proeps.2013.01.058, Vol.6, p. 441-p. 447, Vol.6, pp. 441-447
, 2012.09.
370. Emiko MORIOKA, YU QIANQIAN, Keiko Sasaki, Tsuyoshi Hirajima, Characterization of Lithium Ion Sieve Produced from Biogenic Mn Oxide, International Symposium on Earth Science and Technology 2012 (CINEST2012), p.507-p.510, pp.507-510, 2012.09.
371. Himawan T.B.M., PETRUS, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki OKAMOTO, Alternative Techniques to Separate Tennantite from Chalcopyrite: Single Minerals and Arseno Copper Ore Flotation Study, XXVI International Mineral Processing Congress (IMPC 2012), p. 412, 2012.09.
372. Keiko Sasaki, Naoyuki Fukumoto, Sayo Moriyama, Qianqian Yu, Tsuyoshi Hirajima, Chemical regeneration of magnesium oxide used as a sorbent for fluoride, Separation and Purification Technology, 10.1016/j.seppur.2012.07.028, 98, 24-30, 2012.09, Use of MgO for repeated calcination with regard to its sorption density for F - and chemical stability was examined. Magnesium oxide was produced by the calcination of MgCO 3 at 1273 K for 1 h. The sorption of 9.82 mM F - on the calcined product and the calcinations of solid residues were carried out five times to evaluate trends in sorption density for F - and the stability of the chemically regenerated sorbents. The order of sorption density of F - (Q/mol g -1) apparently seems to depend on the specific surface area. However, Q′ values after normalization of the sorption density for the specific surface area (Q′/mmol m -2) were found to be correlated with the solid basicities of the calcined products which were derived from CO 2-TPD curves for the calcined products. The number of weak base sites, calculated from the peak intensity at 373 K in CO 2-TPD, was considered to be responsible for the removal of F - through hydration. Large quantities of NaMgF 3 and elemental Mg were evaporated by the calcination at 1273 K of the solid residues formed after sorption of F -..
373. Qianqian YU, Keiko Sasaki, Kazuya Tanaka, Toshihiko Ohnuki, Tsuyoshi Hirajima, Structural influences of zinc on the biogenic manganese oxides and concomitant formation of MnO2 nanosheets, Geomicrobiology Journal, 2012.08.
374. Keiko Sasaki, Shoichi Tsuruyama, Sayo Moriyama, Stephanie Handley-Sidhu, Joanna C. Renshaw, Lynne E. Macaskie, Ion Exchange Capacity of Sr2+ onto Calcined Biological Hydroxyapatite
and Implications for Use in Permeable Reactive Barriers, Materials Transactions,, 53, 7, 1267-1272, 2012.07.
375. Qianqian Yu, Keiko Sasaki, Kazuya Tanaka, Toshihiko Ohnuki, Tsuyoshi Hirajima, Structural factors of biogenic birnessite produced by fungus Paraconiothyrium sp.
WL-2 strain affecting sorption of Co2+, Chemical Geology, doi:10.1016/j.chemgeo.2012.03.029, 310-311, 106-113, 2012.07.
376. Keiko SASAKI, Naoyuki FUKUMOTO, Sayo MORIYAMA, Qianqian YU, Tsuyoshi HIRAJIMA, Chemical regeneration of magnesium oxide as a sorbent of fluoride, Separation and Purification Technology, 98, 24-30, 2012.07.
377. Keiko Sasaki, Koichiro Takatsugi, Olli H. Tuovinen, Spectroscopic analysis of the bioleaching of chalcopyrite by Acidithiobacillus caldus, Hydrometallurgy, 127-128, 116-120, 2012.07.
378. YU QIANQIAN, Keiko Sasaki, Kazuya TANAKA, Toshihiko OHNUKI, Tsuyoshi Hirajima, Structural Factors of Biogenic Birnessite Produced by Fungus Paraconiothyrium sp. WL-2 Strain Affecting Sorption of Co2+, Chemical Geology, doi: 10.1016/j.chemgeo.2012.03.029 Vol.310-311, 5, 106-113, 5, pp.106–113, 2012.06.
379. Naoko Okibe, Masaharu KOGA, Keiko Sasaki, Tsuyoshi Hirajima, Shinichi HEGURI, Satoshi ASANO, Simultaneous Oxidation and Immobilization of Arsenite from Refinery Waste Water by Thermoacidophilic Iron-Oxidizing Archaeon, Acidianus brierleyi , Proceedings of Biohydrometallurgy 2012 , 2012.06.
380. Qianqian Yu, Keiko Sasaki, Kazuya Tanaka, Toshihiko Ohnuki, Tsuyoshi Hirajima, Structural factors of biogenic birnessite produced by fungus Paraconiothyrium sp. WL-2 strain affecting sorption of Co 2+, Chemical Geology, 10.1016/j.chemgeo.2012.03.029, 310-311, 106-113, 2012.06, The surface reactivity of biogenic birnessite is attributed to its structure. However, structural control of heavy metal adsorption on biogenic birnessite is not well understood. Here a poorly-crystalline birnessite was produced by the fungus Paraconiothyrium sp. WL-2 strain under ambient pH and temperature conditions. The structure was characterized by X-ray absorption spectroscopy and X-ray diffraction. Sorption behaviors of Co 2+ were compared with Zn 2+. The primary product of the Mn bio-oxidation is hexagonal birnessite with a turbostratic structure. XAFS analysis demonstrated that the biogenic birnessite consists of octahedral sheets with Mn(IV) as the central metal and some vacant sites. Mn(III) atoms are coordinated to some of the vacant sites in the interlayer. The adsorption of Co 2+ by the biogenic birnessite is higher than Zn 2+. The excess adsorption of Co 2+ than Zn 2+ is nearly the same as the excess release of Mn from the biogenic birnessite. These results strongly suggested that the interlayer Mn(III) can oxidize the adsorbed Co 2+ to Co 3+, resulting in excess adsorption of Co 2+ compared to Zn 2+ by biogenic birnessite..
381. Sayo MORIYAMA, Keiko Sasaki, Tsuyoshi Hirajima, Removal of Fluoride on Mg–Al Mixed Oxides Prepared at Different Temperatures, Geochimica Cosmochimica Acta, Vol.74, Issue 12, 1503, 2012.02.
382. Keiko Sasaki, Shoichi TSURUYAMA, Sayo MORIYAMA, Tsuyoshi Hirajima, Sorption of Sr2+ on Hydroxyapatite from Calcined Fish Bones at Different Temperatures, Geochimica Cosmochimica Acta, Vol.74, Issue 12, pp.1799, 2012.02.
383. Tsuyoshi Hirajima, Yuki AIBA, Mohsen Farahat, Naoko Okibe, Keiko Sasaki, Takehiko Tsuruta, Katsumi DOI, Effect of Microorganisms on Flocculation of Quartz, International Journal of Mineral Processing, doi:10.1016/j.minpro.2011.10.001, Vol.102-103, 107-111, 2012.01.
384. Himawan Tri Bayu Murti PETRUS, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki OKAMOTO, Effects of Sodium Thiosulphate on Chalcopyrite and Tennantite; An Insight for Alternative Separation Technique, International Journal of Mineral Processing, dx.doi.org/10.1016/j.minpro.2011.11.002, Vol.102–103, 116-123, 2012.01.
385. Tsuyoshi Hirajima, Yuki Aiba, Mohsen Farahat, Naoko Okibe, Keiko Sasaki, Takehiko Tsuruta, Katsumi Doi, Effect of microorganisms on flocculation of quartz, International Journal of Mineral Processing, 10.1016/j.minpro.2011.10.001, 102-103, 107-111, 2012.01, Application of microorganisms as surface modifiers in flocculation has generated a great deal of interest in recent times. The surface properties such as zeta-potential and hydrophobicity of minerals and microorganisms play a major role in determining the adsorption of microorganisms onto the minerals and hence the efficiency of flocculation. The utility of microorganisms, including Escherichia coli (wild-type and genetically modified strain Sip), Arthrobacter nicotianae, Bacillus licheniformis, and Pseudomonas maltophilia, has been evaluated by measuring their zeta-potentials and carrying out adsorption and flocculation experiments. Of the tested microorganisms, adsorption of E. coli strain Sip significantly modified the quartz surface. The zeta-potential of the quartz became highly positive at acidic pH, and its IEP (isoelectric point) was shifted from pH < 2 to pH 4.3. Moreover, the settling velocity of the bio-treated quartz reached its maximum value at this pH. The number of cells adsorbed onto quartz was low at pH above the IEP due to the identical surface charges of the mineral and bacterial cells. This led to a repulsive force between the mineral particles and bacterial cells, which hindered the adsorption process. For all of the studied strains, the settling velocity of bio-treated quartz was high at their respective IEPs. An interaction model of microorganisms is proposed to explain the flocculation behavior of bio-treated quartz. Potential energies were calculated using the DLVO theory, and the results were found to be in good agreement with the flocculation tests. The settling velocity of the bio-treated quartz was maximized at pH close to the IEP of microbial cells. Interaction between cells is identified as the most likely cause of flocculation of bio-treated quartz..
386. Himawan T B M Petrus, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki Okamoto, Effects of sodium thiosulphate on chalcopyrite and tennantite
An insight for alternative separation technique, International Journal of Mineral Processing, 10.1016/j.minpro.2011.11.002, 102-103, 116-123, 2012.01, In this study, the effects of sodium thiosulphate on chalcopyrite and tennantite at various pH values were investigated. Contact angle, flotation (Hallimond tube), zeta potential and X-ray photoelectron spectroscopy were used to observe these effects and to investigate the mechanisms involved. The addition of sodium thiosulphate depressed both chalcopyrite and tennantite at all pH values. Further addition of diethyl dithiophosphate significantly increased the flotability of chalcopyrite at all pH values as well as tennanite in acidic conditions, but not tennantite in alkaline conditions. In light of the zeta potential measurements and due to the stability of thiosulphate over the pH range, the coverage of sulphate resulting from the oxidation of thiosulphate was responsible for the depression of both chalcopyrite and tennantite in acidic conditions. Adsorption of diethyl dithiophosphate species on the mineral surface resulted in flotability of tennantite which was almost as high as that of chalcopyrite. In alkaline conditions, coverage of the copper thiosulphate complex was responsible for the depression. The copper thiosulphate complex inhibited adsorption of diethyl dithiophosphate species on the mineral surface. Higher coverage of the copper thiosulphate complex on tennantite caused an insignificant increase in its flotability in comparison to that of chalcopyrite which allowed the separation of tennantite from chalcopyrite. The XPS spectra supported the proposed mechanism of thiosulphate depression on these minerals..
387. Characterization of passivation layers in bioleaching of sulfides.
388. Osama Eljamal, Keiko Sasaki, Tsuyoshi Hirajima, Numerical simulation for reactive solute transport of arsenic in permeable reactive barrier column including zero-valent iron, Applied Mathematical Modelling, 10.1016/j.apm.2011.04.040, 35, 10, 5198-5207, 2011.10, Numerical modeling was developed in one dimensional solute transport including chemical reaction to simulate the permeable reactive barrier column results, in which arsenite (As(III)) was removed using zero-valent iron (ZVI). Removal principles of As(III) includes oxidation of As(III) to As(V), sorption of As(III) and sorption of As(V) at least. Each kinetic parameter was drawn in preliminary batch tests to integrate the simulation.The column simulation results show that As(V) adsorption rate was faster than the As(III) adsorption rate and that they are affected by the available mass of Fe(III) in the system. The model can be used to design and predict the long term performance of ZVI permeable reactive barriers (PRBs)..
389. Naoyuki Fukumoto, Keiko Sasaki, Sayo Moriyama, Tsuyoshi Hirajima, Synthesis of Magnesia as a Reusable Sorbent for Fluoride, Journal of Novel Carbon Resource Sciences, 4, 32-35, 2011.09.
390. Himawan T.B.M. Petrus, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki Okamoto, Effect of pH and diethyl dithiophosphate (DTP) treatment on chalcopyrite and tennantite surfaces observed using atomic force microscopy (AFM), Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2011.08.015, 389, 1-3, 266-273, 2011.09, Atomic force microscopy (AFM) has been used to observe the morphology and surface characteristics of chalcopyrite and tennantite treated at pH 4 and 9. Mineral treated with DTP at pH 9 was also observed. It was found that new surface " islands" were formed on the minerals after these treatments. The occurrence of these islands as a product of reaction was amplified with increasing treatment time. Adhesion force measurements revealed that the formation of islands under acidic conditions (pH 4) lowered the adhesion force value compared to that under alkaline conditions (pH 9), thus rendering the surfaces of the minerals more hydrophobic. A similar tendency was observed in the adhesion force value of minerals surface-treated with DTP at pH 9. This phenomenon arose as a result of a propensity for the formation of elemental sulfur or metal-deficient sulfur-rich species at pH 4 and DTP species at pH 9. The more hydrophilic surfaces of both minerals indicated by higher values of the adhesion force after treatment at pH 9 may be attributed to the occurrence of metal hydroxide moieties. From the morphology images and adhesion force, it is apparent that the coverage of islands on the surface of a mineral determines its hydrophobicity or hydrophilicity. Moreover, it also shows the relative reactivities of the minerals, with tennantite being more reactive than chalcopyrite. Furthermore, the microscopic observation by AFM was consistent with the macroscopic observations of contact angle and flotability studies..
391. H. T.B.M. Petrus, Tsuyoshi Hirajima, Keiko Sasaki, H. Okamotob, Study of diethyl dithiophosphate adsorption on chalcopyrite and tennantite at varied phs, Journal of Mining Science, 10.1134/S1062739147050194, 47, 5, 695-702, 2011.09, The kinetics of diethyl dithiophosphate adsorption on chalcopyrite and tennantite has been studied by UV-visible spectroscopy at pH values of 4, 6, and 9. The concentration of diethyl dithiophosphate in the solution has been monitored as a function of time and pH for both minerals. It was found that the adsorption tendency of diethyl dithiophosphate on both minerals decreased with the increasing pH treatments. This is due to the existence of metal hydroxide species onto the mineral surface in more alkaline condition inhibiting the adsorption of diethyl dithiophosphate species. In comparison to that of chalcopyrite, tennantite possessed slightly higher adsorption of diethyl dithiophosphate in acid condition, while vice versa correlation observed at other pH treatments at where the coverage of metal hydroxide species obtained higher than that of chalcopyrite showing that the rate oxidation of tennantite is higher. An adsorption mechanism has been proposed and tested against the experimental kinetic data. Both the kinetic data and flotation studies are consistent with the proposed mechanism..
392. Moriyasu Nonaka, Tsuyoshi Hirajima, Keiko Sasaki, Upgrading of low rank coal and woody biomass mixture by hydrothermal treatment, Fuel, 10.1016/j.fuel.2011.03.028, 90, 8, 2578-2584, 2011.08, Attempts to produce high-grade fuel from biomass and low rank coal are important from the viewpoint of renewable energy and the utilization of unused resources. In this paper, the authors reported on the hydrothermal treatment of biomass and low rank coal at 300 °C using a bench scale continuous apparatus and a batch autoclave. The results show that coalification takes place during the hydrothermal treatment of both the low rank coal and biomass, and the upgraded solid products show similar chemical compositions, gross calorific value and effective calorific value, independent of the mixing ratio. The solid product also becomes hydrophobic and unable to re-adsorb the lost moisture. The characteristics of the solid produced by the bench scale continuous apparatus can be predicted by the results of the batch process. Thermogravimetric analysis shows that the solid product has a wide-range of molecular weight but the thermally stable heavy molecules are found more in the treated coal as opposite to the thermally unstable light molecules, more of which are found in the treated biomass. This may correlate with that the solid product of higher biomass mixing ratio has a higher volatile matter content. Polymerization is synergistically promoted during mixed hydrothermal treatment of low rank coal and biomass..
393. S. Handley-Sidhu, J. C. Renshaw, S. Moriyama, B. Stolpe, C. Mennan, S. Bagheriasl, P. Yong, A. Stamboulis, M. Paterson-Beedle, K. Sasaki, R. A.D. Pattrick, J. R. Lead, L. E. MacAskie, Uptake of Sr 2+ and Co 2+ into biogenic hydroxyapatite
Implications for biomineral ion exchange synthesis, Environmental Science and Technology, 10.1021/es2015132, 45, 16, 6985-6990, 2011.08, Biomineral hydroxyapatite (Bio-HAp) produced by Serratia sp. has the potential to be a suitable material for the remediation of metal contaminated waters and as a radionuclide waste storage material. Varying the Bio-HAp manufacturing method was found to influence hydroxyapatite (HAp) properties and consequently the uptake of Sr 2+ and Co 2+. All the Bio-HAp tested in this study were more efficient than the commercially available hydroxyapatite (Com-HAp) for Sr 2+ and Co 2+ uptake. For Bio-HAp the uptake for Sr 2+ and Co 2+ ranged from 24 to 39 and 29 to 78 mmol per 100 g, respectively. Whereas, the uptake of Sr 2+ and Co 2+ by Com-HAp ranged from 3 to 11 and 4 to 18 mmol per 100 g, respectively. Properties that increased metal uptake were smaller crystallite size (<40 nm) and higher surface area (>70 m 2 g -1). Organic content which influences the structure (e.g., crystallite arrangement, size and surface area) and composition of Bio-HAp was also found to be important in Sr 2+ and Co 2+ uptake. Overall, Bio-HAp shows promise for the remediation of aqueous metal waste especially since Bio-HAp can be synthesized for optimal metal uptake properties..
394. Handley-Sidhu S, Renshaw J.C, Sayo MORIYAMA, Stolpe B, Yong P, Mennan C, Bagheriasl S, Stamboulis A, Paterson-Beedle M, Keiko SASAKI, Pattrick R.A.D, Lead J.R, Macaskie L.E., Removal of Sr2+ and Co2+ into Biogenic Hydroxyapatite: Implications for Biomineral Ion Exchange Synthesis, Environmental Science and Technology, 45, 6985-6990, 2011.07.
395. Shoichi TSURUYAMA, Keiko SASAKI, Tsuyoshi HIRAJIMA, Sorption characteristics of F- on hydroxyapatite from calcined fish bone at various temperatures, Proc. CINEST 2011, 2011.07.
396. Emiko Morioka, Qianqian Yu, Keiko Sasaki, Recovery of lithium ion using calcined products from biogenic birnessite, Proc. CINEST 2011, 2011.07.
397. Keiko Sasaki, Naoyuki Fukumoto, Sayo Moriyama, Tsuyoshi Hirajima, Sorption characteristics of fluoride on to magnesium oxide-rich phases calcined at different temperatures, Journal of Hazardous Materials, 10.1016/j.jhazmat.2011.04.071, 191, 1-3, 240-248, 2011.07, The effect of calcination temperature during production of magnesium oxide-rich phases from MgCO3 on the sorption of F- ions in the aqueous phase has been investigated. Magnesium oxide-rich phases were formed by calcination at over 873K for 1h. Higher calcination temperatures produced more crystalline MgO with smaller specific surface area and provided larger values of the total basicity per unit surface area. The higher calcination temperatures lead to slower F- removal rate, and lower equilibrium F- concentrations, when the equilibrium F- concentrations are less than 1mmoldm-3. Larger total basicity per unit surface area made the reactivity with F- ions in aqueous phase more feasible, resulting in a greater degree of F- sorption. For equilibrium F- concentrations more than 1mmoldm-3, lower calcination temperatures favored the co-precipitation of F- with Mg(OH)2, probably leading to the formation of Mg(OH)2-xFx, and the achievement of larger sorption density. This is the first paper which describes the relationship between the solid base characteristics obtained by CO2-TPD for MgO with different calcination temperatures as a function of the reactivity of F- sorption in the aqueous phase..
398. Koichiro Takatsugi, Keiko Sasaki, Tsuyoshi Hirajima, Mechanism of the enhancement of bioleaching of copper from enargite by thermophilic iron-oxidizing archaea with the concomitant precipitation of arsenic, Hydrometallurgy, 10.1016/j.hydromet.2011.05.013, 109, 90-96, 2011.05.
399. Keiko Sasaki, Koichiro Takatsugi, Tsuyoshi Hirajima, Effects of initial Fe2+ concentration and pulp density on the bioleaching of Cu from enargite by Acidianus brierleyi, Hydrometallurgy, 10.1016/j.hydromet.2011.06.008, 109, 153-160, 2011.05.
400. Keiko Sasaki, Naoyuki Fukumoto, Sayo Moriyama, Tsuyoshi Hirajima, Sorption characteristics of fluoride on to magnesium oxide-rich phases calcined at different temperatures, Journal of Hazardous Materials, 191, 240-248, 2011.04.
401. Moriyasu NONAKA, Tsuyoshi HIRAJIMA and Keiko SASAKI, Upgrading of Low Rank Coal and Woody Biomass Mixture by Hydrothermal Treatment, Fuel, in press, 2011.04.
402. Keiko SASAKI, Hitoshi TAKAMORI, Sayo MORIMAYA, Hitoshi YOSHIZAKA, Tsuyoshi HIRAJIMA, Effect of Saw Dusts on Borate Removal from Groundwater in Bench-scale Simulation of Permeable Reactive Barriers Including Magnesium Oxide, Journal of Hazardous Materials, https://doi.org/10.1016/j.jhazmat.2010.10.067, Vol.185, Issues 2-3, 1440-1447, 2011.01.
403. H.T.B.M. Petrus, Tsuyoshi Hirajima, Yuji Oosako, Moriyasu Nonaka, Keiko Sasaki, Takashi Ando, Performance of dry-separation processes in the recovery of cenospheres from fly ash
and their implementation in a recovery unit, International Journal of Mineral Processing, 98 (2011) 15–23, 2011.01.
404. Anggoro Tri Mursito, Tsuyoshi Hirajima, Keiko Sasaki, Alkaline hydrothermal de-ashing and desulfurization of low quality coal
and its application to hydrogen-rich gas generation, Energy Conversion and Management, 52, 762-769, 2011.01.
405. Himawan Tri Bayu Murti PETRUS, 平島 剛, 笹木 圭子, Effect of pH and Diethyl Dithiophosphate (DTP) Treatment on Chalcopyrite and
Tennantite Surface Observed Using Atomic Force Microscopy (AFM), Colloids and Surface A: Physicochemical and Engineering Aspects, 2011, 9, Vol.389, Issues 1-3, pp.266-273, 2011.01.
406. H. T. B. M. Petrus, T. Hirajima, K. Sasaki, H. Okamoto, Study of Diethyl Dithiophosphate Adsorption on Chalcopyrite and Tennantite at Varied pHs, Journal of Mining Science, 47, 5, 695-702, 2011.01.
407. Anggoro Tri Mursito, Tsuyoshi Hirajima, Keiko Sasaki, Alkaline hydrothermal de-ashing and desulfurization of low quality coal and its application to hydrogen-rich gas generation, Energy Conversion and Management, 10.1016/j.enconman.2010.08.001, 52, 1, 762-769, 2011.01, This paper describes experimental research and a fundamental study of alkaline hydrothermal treatment of high-sulfur, high-ash coal from Banten, Java-Indonesia. Experiments were carried out on a laboratoryscale 0.5 L batch reactor. The alkaline hydrothermal treatment gave upgraded clean coal with low sulfur content (about 0.3 wt.%) and low ash content (about 2.1 wt.%). A zero carbon dioxide and pure hydrogen gas were produced at 330 °C by introducing an alkali (sodium hydroxide, NaOH) to the hydrothermal treatment of raw coal. X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques were used to test for the removal or reduction of major inorganic elements in the coal, and changes in carbon-functional groups and their properties were determined by Fourier transform infrared spectroscopy (FTIR) and Carbon-13 of nuclear magnetic resonance (13C NMR) tests on the product of the hydrothermal upgrading and demineralization process..
408. Keiko Sasaki, Characterization of passivation layers in bioleaching of sulfides, bunseki kagaku, 10.2116/bunsekikagaku.60.911, 60, 12, 911-919, 2011.01, During the process for the bioleaching of sulfides, the surface of the target mineral is sometimes covered with intermediates, and the final products that interfere with the extraction of the target metal. Understanding the characterization and formation order of the secondary minerals responsible for passivation is a key to resolving the passivation mechanism. The present article reviews identification of secondary minerals and intermediates in a process of bioleaching of several sulfides by X-ray photoelectron spectroscopy, Raman spectroscopy, identification of the jarosite group minerals using Raman spectroscopy, and expectation of the formation order of the secondary minerals by SEM-EDX and TEM. The TEM observation in a nano-domain provides useful information about amorphous the secondary minerals. A passivation model was proposed to keep maximizing Cu recovery and minimizing As solubilization for the bioleaching of arsenic-bearing copper sulfides using super-thermophilic archaea, which are expected to be new target minerals in the near future..
409. Keiko Sasaki, H. Takamori, S. Moriyama, H. Yoshizaka, Tsuyoshi Hirajima, Effect of saw dust on borate removal from groundwater in bench-scale simulation of permeable reactive barriers including magnesium oxide, Journal of Hazardous Materials, 10.1016/j.jhazmat.2010.10.067, 185, 2-3, 1440-1447, 2011.01, Effective immobilization of boron in groundwater is a major challenge. Permeable reactive barrier (PRB) column tests for removal of borate have been investigated using MgO agglomerates as the primary reactive material over 40 weeks. Additionally, saw dust was also blended with MgO agglomerates to facilitate for borate removal in this system. Boron accumulation was more than 1.6 times greater in the presence of saw dust, although MgO alone performed well. Increased boron accumulation in the presence of saw dust was primarily due to higher porosity of the PRB column, decreasing the impact of secondary Mg(OH)2 passivating layers and leaving more reactive sites on MgO agglomerates. In addition, Mg2+ ions released from MgO agglomerates are complexed with carboxylic acids leached from saw dusts. This sequestration prevents the formation of bulky Mg(OH)2 which is an ineffective sorbent for borate and covers the surfaces and passivating reactive sites on the MgO agglomerates. The morphologies of Mg(OH)2 precipitated in the PRB column were also significantly affected by the presence of saw dust, with crystallization of needle-like particles of Mg(OH)2 was prevented by Mg2+ ions-organic ligand complexation..
410. H. T.B.M. Petrus, Tsuyoshi Hirajima, Yuji Oosako, Moriyasu Nonaka, Keiko Sasaki, Takashi Ando, Performance of dry-separation processes in the recovery of cenospheres from fly ash and their implementation in a recovery unit, International Journal of Mineral Processing, 10.1016/j.minpro.2010.09.002, 98, 1-2, 15-23, 2011.01, Cenospheres recovery is one of the coal fly ash beneficiations, providing economic as well as environmental benefits. Current techniques, such as lagoon or other wet-separation processes, consume large amounts of water and add to water pollution due to leaching of toxic materials from fly ash. The other possible disadvantage is the need for a wide operational area, which is unsuitable for densely populated countries. As wet-separation processes have some disadvantages, an improved and/or sustainable alternative recovery technique is required. An air classifier is one of the alternative techniques. In this study, two types of air classifiers, namely a closed-type pneumatic separator and a micron separator, have been investigated. In terms of separation efficiency, it was found that the micron separator has the potential to be applied in cenospheres recovery from coal fly ash, giving a Newton's efficiency of 0.44, as compared to a value of about 0.26 for the closed-type pneumatic separator. The cenospheres recoveries of both pieces of equipment at their optimum Newton's efficiencies were similar at over 60 wt.%. The separation performance was further assessed from the particle distributions of the overflow and underflow products obtained from both pieces of equipment, as well as from SEM images. It was found that the lower Newton's efficiency of the closed-type pneumatic separator was due to the re-concentration of fine particles in the underflow product at air-flow rates higher than 2.2 m/s (the underflow product yield was about 55 wt.%). In order to further confirm the applicability of this technique, the micron separator, which had provided higher separation efficiency and cenospheres recovery, was deployed in a cenospheres recovery unit prior to the use of a wet-separation process (float and sink tank). About 80% of the cenospheres was recovered, with an 87.8% reduction in the total mass of fly ash to be separated in the float and sink tank. Consequently, much less water was needed for the process of cenospheres recovery. Moreover, it was also confirmed that the micron separator could yield higher quality fly ashes, that is, fly ash types I and II, from lower feed quality of fly ash type IV, which is the lowest category in commercial classification of fly ash according to JIS A6201..
411. OSAMA ELJAMAL , KEIKO SASAKI, Shoichi Tsuruyama, TSUYOSHI HIRAJIMA, Kinetic Model of Arsenic Sorption onto Zero-Valent Iron, Water Quality, Exposure and Health, DOI 10.1007/s12403-010-0030-7, in press, 2010.12.
412. Ahmad T. YULIANSYAH, Tsuyoshi HIRAJIMA, Satoshi KUMAGAI, Keiko SASAKI, Production of Solid Biofuel from Agricultural Wastes of the Palm Oil Industry by Hydrothermal Treatment, Waste and Biomass Valorization, in press, 2010.12.
413. M. Farahat, T. Hirajima, K. Sasaki, K. Doi, Adhesion of Escherichia coli onto oxide minerals - extended dlvo theory and Flotation behaviour, 25th International Mineral Processing Congress 2010, IMPC 2010 XXV International Mineral Processing Congress 2010, IMPC 2010, 1841-1851, 2010.12, The adhesion behaviour of Escherichia coli to three oxide minerals (quartz, hematite and corundum) was investigated experimentally. A strain of E. coli was used that contains genes encoding a protein involved in silica precipitation. Maximum cell adhesion was observed at pH <4.3 for quartz and at pH 4.5 - 8.5 for corundum. Cell adhesion to hematite remained low at all pHs. Microbe-mineral adhesion was assessed with an extended DLVO theory approach. The essential parameters used to calculate the energy of the microbe-mineral interaction (Hamaker constants and acid-base components) were experimentally determined. The extended DLVO approach can be used to explain the results of the adhesion experiments. The effect of E coli on the floatability of the three oxide minerals was determined. Our results showed that Ecoli can act as a selective collector for quartz at acidic pHs, with 90 per cent of the quartz floated at 1.5 × 109 cells/mL. However, only 9 per cent of hematite and 30 per cent of corundum was floated under similar conditions. Using E coli and no reagents, it was possible to separate quartz from a hematite-quartz mixture with a Newton's efficiency of 0.7. Quartz was removed from a corundum mixture by E coli with a Newton's efficiency of 0.6..
414. T. Yuliansyah Ahmad, Tsuyoshi Hirajima, Satoshi Kumagai, Keiko Sasaki, Production of solid biofuel from agricultural wastes of the palm oil industry by hydrothermal treatment, Waste and Biomass Valorization, 10.1007/s12649-010-9045-3, 1, 4, 395-405, 2010.12, In this study, upgrading of agricultural waste, in the form of oil palm fronds and trunks, into solid biofuel was investigated using hydrothermal treatment. A slurry of 300 mL of water and 30 g of material was treated in a 500-mL batch autoclave equipped with stirrer, thermometer, and pressure sensor. Experiments were conducted in the temperature range 200-350°C at an initial pressure of 2.0 MPa. The slurry was gradually heated to the target temperature and held for a further 30 min. Approximately 35-65% of the original material was recovered as a solid product with favorable solid fuel characteristics. The gross calorific value ranged from 19.9 to 29.7 MJ/kg and the equilibrium moisture content was 7.6-4.5 wt%. The carbon content varied from 51.4 to 78.5 wt% and the oxygen content was 42.1-16.1 wt% after upgrading. Changes in the solid composition and carbon functional groups following upgrading were identified by FTIR and 13C NMR. In addition, analyses on the liquid product (by GC-MS) and the gas product (by GC) were carried out to clarify the decomposition behavior of material..
415. K. Sasaki, K. Takatsugi, T. Hirajima, Several approaches to enhance the bioleaching of enargite, 25th International Mineral Processing Congress 2010, IMPC 2010 XXV International Mineral Processing Congress 2010, IMPC 2010, 487-497, 2010.12, Some approaches were investigated to enhance the recovery of Cu from enargite by bioleaching with Acidithiobacillus ferrooxidans using the galvanic interaction with pyrite and activated carbon, and with thermophilic bacteria, Acidianus brierleyi. Addition of pyrite initially enhanced Cu leaching by the Galvanic effect, but after that the formation of secondary minerals passivated the surface of enargite in inoculated batches. Activated carbon improved Cu recovery from enargite much better than pyrite, when it is contacted with enargite. Recovery of Cu from enargite has been recorded to at largest 2.4 per cent within 30 days in the presence of activated carbon when mesophilic bacteria were inoculated at 25°C. The recovery of Cu from enargite was drastical ly enhanced by inoculation of thermophilic bacteria, Acidianus brierleyi, up to 60 per cent within 40 days at 70°C and still not leveled off after 40 days unless the formation of Fe(III) precipitates occurred. After 40 days dissolved molar ratio of Cu/As is around 5.2, suggesting that metal-defi cient sulfi des and/or ferric arsenate might be formed on the surface of enargite..
416. Anggoro Tri Mursito, Tsuyoshi Hirajima, Keiko Sasaki, Satoshi Kumagai, The effect of hydrothermal dewatering of Pontianak tropical peat on organics in wastewater and gaseous products, Fuel, 10.1016/j.fuel.2010.06.035, 89, 12, 3934-3942, 2010.12, This paper describes a study of the effects of hydrothermal dewatering of raw tropical peat from Pontianak, West Kalimantan-Indonesia, on the amounts of organic compounds released into wastewater and gaseous products. Hydrothermal upgrading and dewatering of the peat was carried out in a batch-type autoclave reactor at temperatures between 150 and 380 °C at a maximum pressure of 25.1 MPa for 30 min. It was found that the extent of decomposition of organics during hydrothermal dewatering depended on temperature increase. Wastewater from hydrothermal dewatering was found to contain organic carbon (TOC) ranging from 800 ppm at low temperatures, to 7504 ppm at high temperatures. A number of sugars and furans were detected in the wastewater at 250 °C, and organic acids and alcohols at all temperatures. Phenol and phenolic derivatives were observed at 250 °C, and significant amounts of CO2, CO and H 2 were detected at all temperatures studied; CH4 was detected only at 380 °C, but at this temperature CO2 was no longer detected. A simplified schematic diagram of the decomposition behavior of tropical peat in the hydrothermal dewatering process is discussed with respect to the change in the concentration of organics in wastewater and gaseous products as determined by TOC, GC, GC-MS and 13C NMR analyses of the solids produced..
417. Himawan Tri Bayu Murti PETRUS, Tsuyoshi Hirajima, Keiko Sasaki, UV-Vis Spectrophotometry and AFM Observation of Diethyl Dithiophosphate Adsorption on Chalcopyrite at Varied pHs, Journal of Chemistry and Chemical Engineering, 2011, 11, Vol.5, Number 11, pp.1006-1013, 2010.11.
418. Mohsen Farahat, Tsuyoshi Hirajima, Keiko Sasaki, Adhesion of Ferroplasma acidiphilum onto pyrite calculated from the extended DLVO theory using the van Oss-Good-Chaudhury approach, Journal of Colloid And Interface Science, 10.1016/j.jcis.2010.05.091, 349, 2, 594-601, 2010.09, The adhesion behavior of Ferroplasma acidiphilum archaeon to pyrite mineral was investigated experimentally and theoretically. F. acidiphilum showed high affinity to adhere to pyrite surface at acidic regions, however low affinity was observed at neutral and alkaline regions. The microbe-mineral adhesion was assessed by the extended DLVO theory. Hamaker constants, electron donors, electron acceptors and surface charges for the microbe and the mineral were experimentally determined. The extended DLVO theory was used to explain the adhesion results. Significant changes to the pyrite surface properties after being treated with the microbial cells were observed. Pyrite lost its hydrophobic nature and became hydrophilic, the contact angle of untreated pyrite was 61° and this decreased to 36° after the treatment. As a consequence, the flotation experiment results showed that F. acidiphilum strain could act as a good depressant for pyrite in xanthat flotation; where in absence of F. acidiphilum cells, over 95% of pyrite can be recovered as a float. However, when the mineral was pretreated with F. acidiphilum cells, less than 20% can be recovered as a float..
419. M. A. Halim, R. K. Majumder, S. A. Nessa, Y. Hiroshiro, K. Sasaki, B. B. Saha, A. Saepuloh, K. Jinno, Evaluation of processes controlling the geochemical constituents in deep groundwater in Bangladesh
Spatial variability on arsenic and boron enrichment, Journal of Hazardous Materials, 10.1016/j.jhazmat.2010.01.008, 180, 1-3, 50-62, 2010.08, Forty-six deep groundwater samples from highly arsenic affected areas in Bangladesh were analyzed in order to evaluate the processes controlling geochemical constituents in the deep aquifer system. Spatial trends of solutes, geochemical modeling and principal component analysis indicate that carbonate dissolution, silicate weathering and ion exchange control the major-ion chemistry. The groundwater is dominantly of Na-Cl type brackish water. Approximately 17% of the examined groundwaters exhibit As concentrations higher than the maximum acceptable limit of 10μg/L for drinking water. Strong correlation (R2=0.67) of Fe with dissolved organic carbon (DOC) and positive saturation index of siderite suggests that the reductive dissolution of Fe-oxyhydroxide in presence of organic matter is considered to be the dominant process to release high content of Fe (median 0.31mg/L) in the deep aquifer. In contrast, As is not correlated with Fe and DOC. Boron concentration in the 26% samples exceeds the standard limit of 500μg/L, for water intended for human consumption. Negative relationships of B/Cl ratio with Cl and boron with Na/Ca ratio demonstrate the boron in deep groundwater is accompanied by brackish water and cation exchange within the clayey sediments..
420. Keiko SASAKI, Qianqian YU, Takuya KASAYAMA, Sorption Characterization of Co2+ Ions on Biogenic Birnessite: Comparison with Synthetic Analogues, Geochim. Cosmochim. Acta, , 74(12S) , A911 , 2010.07.
421. Sayo MORIYAMA, Keiko SASAKI, Tsuyoshi HIRAJIMA, Mechanism of Immobilization of Borate on Magnesium Oxide, Geochim. Cosmochim. Acta, 74(12S), A726, 2010.07.
422. LYNNE MACASKIE, P.YONG, STEPHANIE HANDLEY-SIDHU, SAYO MORIYAMA, KEIKO SASAKI, JOE C. RENSHAW, Biogenic hydroxyapatite: new nanophase material for radiodionuclide removal, Geochim. Cosmochim. Acta, 74(12S), A651, 2010.07.
423. JOE C. RENSHAW, STEPHANIE HANDLEY-SIDHU, SAYO MORIYAMA, KEIKO SASAKI, LYNNE MACASKIE, Microbial Biominerals: Role in Radionuclide Remediation, Geochim. Cosmochim. Acta, 74(12S), A863, 2010.07.
424. Abdul M. HALIM, R. K. MAJUMDER, S. A. NESSA, Y. HIROSHIRO, Keiko SASAKI, B. B. SAHA, A. SAEPULOH, Kenji JINNO, Trace metals in water and sediment from coal mine discharge canal in the Boropukuria, Bangladesh: mobility and environmental significance assessment, J. Hazardous Mater., in press, 2010.07.
425. Keiko SASAKI, Koichiro TAKATSUGI, Tsuyoshi HIRAJIMA, Kenji KANEKO, Toshihiko OHNUKI, , Olli H. TUOVINEN, Characterization of secondary formed As-bearing precipitates in bioleaching of enargite by As-adapted Acidithiobacillus ferrooxidans, Hydrometallurgy, 104, 424-431, 2010., 2010.07.
426. Keiko Sasaki, K. Takatsugi, Kenji Kaneko, N. Kozai, T. Ohnuki, O. H. Tuovinen, Tsuyoshi Hirajima, Characterization of secondary arsenic-bearing precipitates formed in the bioleaching of enargite by Acidithiobacillus ferrooxidans, Hydrometallurgy, 10.1016/j.hydromet.2009.12.012, 104, 3-4, 424-431, 2010.07, The purpose of this study was to characterize secondary minerals that were formed in the bioleaching of enargite (Cu3AsS4) by Acidithiobacillus ferrooxidans. Two parallel cultures were used: one was adapted to arsenic in the growth medium and the other was wild-type. The progress of the solubilization of As in A. ferrooxidans cultures was stepwise and different from that observed in the non-adapted culture. In contrast, the bioleaching of Cu and Fe from enargite was not affected by prior adaptation of the culture. Minor presence of jarosite was observed by X-ray diffraction (XRD) in solid residues after the bioleaching, and no other peaks of secondary crystalline minerals were detected. The relative intensities of As 3d and Fe 2p to Cu 2p in X-ray photoelectron spectroscopy (XPS) for the solid residues were at maximum at 46 days after the bioleaching with As-adapted A. ferrooxidans. The results from the examination of solid residues with XPS, transmission electron microscopy with energy-dispersive microprobe (TEM-EDS) and XRD after 46 days of contact with As-adapted A. ferrooxidans showed the presence of metastable, amorphous ferric arsenate as an intermediate on the surface of enargite and minor amounts of jarosite. The amorphous ferric arsenate phase did not appear to have an adverse effect of the dissolution of Cu from enargite..
427. Tsuyoshi Hirajima, H. T.B.M. Petrus, Yuji Oosako, Moriyasu Nonaka, Keiko Sasaki, Takashi Ando, Recovery of cenospheres from coal fly ash using a dry separation process
Separation estimation and potential application, International Journal of Mineral Processing, 10.1016/j.minpro.2010.03.004, 95, 1-4, 18-24, 2010.07, The degree of separation in the recovery of cenospheres from coal fly ash has been estimated for both wet and dry separation processes by applying the terminal velocity concept of particles. Particle diameter and density were determined by sieving industrial cenospheres and coal fly ash type IV, the model particles. This information was then utilized to calculate the terminal velocity needed to estimate the separation performances of both the wet and dry separation processes. Based on this estimation, the dry separation process performed similarly to the wet separation process, with an optimum Newton's efficiency of 0.54, only slightly lower than that of the wet separation process of 0.6. Moreover, it was observed that the cenospheres were concentrated in the underflow product, whereas for the wet separation process the reverse was true. The findings of this assessment were verified using a micron separator. Similar tendencies in the concentration of cenospheres in the underflow products were obtained. An optimum Newton's efficiency as high as 0.44 was achieved, with 66% recovery of the cenospheres. The recovery of the cenospheres was only 4% lower than the estimated value (70%), from which we conclude that dry separation processes are interesting technologies to apply to the recovery of cenospheres from coal fly ash because of their high efficiencies..
428. M. A. Halim, R. K. Majumder, S. A. Nessa, K. Oda, Y. Hiroshiro, B. B. Saha, K. Sasaki, K. Jinno, Evaluation of processes controlling the geochemical constituents in deep groundwater in Bangladesh: spatial variability on arsenic and boron enrichment
, Journal of Hazardous Materials, 180, 50-62, 2010.06.
429. Mohsen FARAHAT, Tsuyoshi HIRAJIMA, Keiko SASAKI, Adhesion of Ferroplasma acidiphilum onto Pyrite Calculated from the Extended DLVO Theory using the Van Oss-Good-Chaudhury Approach, Journal of Colloid & Interface Science, 349, 594-601, 2010.06.
430. Tsuyoshi Hirajima, H.T.B.M. Petrus, Yuji Oosako, Moriyasu Nonaka, Keiko Sasaki, Takashi Ando, Recovery of cenospheres from coal fly ash using a dry separation process: Separation estimation and potential application, International Journal of Mineral Processing, 95, 18-24, 2010.06.
431. Anggoro Tri MURSTO, Tsuyoshi HIRAJIAM, Keiko SASAKI, Satoshi KUMAGAI, The effect of hydrothermal dewatering of Pontianak tropical peat on organics in wastewater and gaseous products, Fuel, in press, 2010.06.
432. K. SASAKI, K. TAKATSUGI, T. HIRAJIMA, Some Approaches to Enhance the Bioleaching of Enargite., Proc. The XXV International Mineral Processing Congress 2010, in press, 2010.05.
433. Anggoro Tri Mursito, Tsuyoshi Hirajima, Keiko Sasaki, Upgrading and dewatering of raw tropical peat by hydrothermal treatment, Fuel, 10.1016/j.fuel.2009.07.004, 89, 3, 635-641, 2010.03, In this study, hydrothermal upgrading and dewatering of raw tropical peat derived from Pontianak, West Kalimantan-Indonesia was evaluated at temperatures ranging from 150 to 380 °C, a maximum final pressure of 25.1 MPa and a residence time of 30 min. The moisture content of the raw peat was approximately 90 wt.%. Raw peat was hydrothermally upgraded without the addition of water in the laboratory scale. The yield of the solid products was between 53.0 and 99.7 wt.% and the effective calorific value of hydrothermally dewatered peat was between 17,290 and 29,209 kJ/kg following hydrothermal upgrading. In addition, the oxygen content in the solid product was varied from 38.4 to 15.6 wt.% after upgrading, while the carbon content from 55.2 to 77.8 wt.%. The hydrothermally upgraded peat fuel product also had an equilibrium moisture content of 2.3 wt.% and a maximum equilibrium moisture content of 17.6 wt.%. Upgraded peat is characteristically resistant to moisture adsorption at high humidity, which makes it promising for fuel based combustion. The change in the carbon-functional groups and their properties, as determined by FTIR and 13C NMR, are discussed in terms of the hydrothermal upgrading and dewatering process..
434. Pauliina Nurmi, Özkaya Bestamin, Keiko Sasaki, Anna H. Kaksonen, Marja Riekkola-Vanhanen, Olli H. Tuovinen, Jaakko A. Puhakka, Biooxidation and precipitation for iron and sulfate removal from heap bioleaching effluent streams, Hydrometallurgy, 10.1016/j.hydromet.2009.11.004, 101, 1-2, 7-14, 2010.02, Effluents from bioleaching processes cause severe problems if dispersed in the environment since they typically have very low pH values and high sulfate and ferric iron concentrations. Dissolved iron may also interfere with the metal recovery. In the bioleaching circuit, partial removal of dissolved iron and sulfate is needed to alleviate process disturbances. In this study, an integrated, bench-scale process comprising a fluidized-bed reactor (FBR) and a gravity settler was developed for controlled biological oxidation of ferrous iron and precipitative removal of ferric iron and sulfate for use in waste management of heap bioleaching processes. The FBR for iron oxidation by an enrichment culture dominated by Leptospirillum ferriphilum was operated at 37 ± 2 °C. The FBR recycle liquor was partially neutralized with 10 M KOH or 50 g/L CaCO
3
slurry to promote ferric iron and sulfate precipitation. With 6 ± 1.5 g Fe
2+
/L in the feed and KOH-adjusted pH 3.5, the oxidation rate of Fe
2+
was 3.7 g/L h and 99% precipitation of ferric iron was achieved in the process. Adjustment with CaCO
3
to pH 3.2 slightly decreased the oxidation rate to 3.3 g/L h and 98% of ferric iron precipitated. With 15 g Fe
2+
/L in the feed, the oxidation rate was 7.0 g Fe
2+
/L h coupled with 96% precipitation of ferric iron. A solid solution of jarosite was the main product of ferric iron precipitation with KOH adjustment and with minor amounts of goethite at the higher pH range. Adjustment of the pH with CaCO
3
precipitated ferric iron also as a solid solution of jarosite, and sulfate precipitated also in the form of gypsum (CaSO
4
·2H
2
O) especially at the higher pH values..
435. Keiko SASAKI, Koichiro TAKATSUGI, Kazuhiro ISHIKURA, Tsuyoshi HIRAJIMA, Spectroscopic study on oxidative dissolution of chalcopyrite, enargite and tennantite at different pHs, Hydrometallurgy, 100, 144-151, Vol. 100, pp.144-151, 2010, 2010.01.
436. Pauliina NURMI, Bestamin ÖZKAYA, Keiko SASAKI, Anna H. KAKSONEN, M.-R. Riekkola-VANHANEN, Olli H. TUOVINEN, Jaakko A. PUHAKKA, Biooxidation and Precipitation for Iron and Sulfate Control in Heap Bioleaching Waste Streams, Hydrometallurgy, 101, 7-14, 2010.01.
437. Anggoro T MURSITO, Tsuyoshi HIRAJIMA, Keiko SASAKI, Upgrading and Dewatering of Raw Tropical Peat by Hydrothermal Treatment, Fuel, 89, 635-641, 2010.01.
438. Keiko Sasaki, Koichiro Takatsugi, Kazuhiro Ishikura, Tsuyoshi Hirajima, Spectroscopic study on oxidative dissolution of chalcopyrite, enargite and tennantite at different pH values, Hydrometallurgy, 10.1016/j.hydromet.2009.11.007, 100, 3-4, 144-151, 2010.01, Chalcopyrite (CuFeS2) occurs sometimes in association with As-bearing copper ores, such as enargite (Cu3AsS4) and tennantite (Cu12As4S13), especially in deep ore bodies. To employ oxidative pretreatment for recovering copper resources from these minerals, it is important to characterize the surface properties of enargite and tennantite as well as chalcopyrite. The minerals were oxidized in 0.013% H2O2 with O2 bubbling at pH 2, 5, and 11 followed by analysis with X-ray photoelectron spectroscopy. Elemental sulfur was formed most significantly at pH 2 in all sulfide mineral samples. Enargite was the most stable under the oxidative conditions. Arsenic in enargite was partly oxidized at pH 5. Substantial proportion of copper in tennantite was oxidized from Cu(I) to Cu(II) at pH 11. The dissolution rate of Cu from tennantite at pH 2 was by far the fastest, and incongruent dissolution of Cu occurred with suppression of As and S in tennantite. These selective differences in the oxidation may be of use in designing a flotation process for separation of these sulfide minerals..
439. H. Petrus, T. Hirajima, Y. Oosako, Moriyasu Nonaka, Keiko Sasaki, T. Ando, Performance of dry separation processes in cenospheres recovery from coal fly ash, 25th International Mineral Processing Congress 2010, IMPC 2010 XXV International Mineral Processing Congress 2010, IMPC 2010, 5, 3863-3871, 2010, Many researchers have recently been very interested in the recovery of valuable materials from fly ash. One of them is cenospheres, which are beneficial for light weighted material components due to their physical and chemical characteristics. Cenospheres recovery technologies are mostly based on wet separation process due to their density, which is lower than water density. Meanwhile the possibility of dry separation process has not yet been fully explored. In contrast to wet separation, a dry separation process provides substantial benefits. These benefits include: much less land consumption and reduced levels of pollution related to the leaching of toxic materials from coal fly ash. In this study, experimental work has been conducted using two types of dry separation processes: a pneumatic separator closed type and a micron separator. Comparing the two alternative techniques, the micron separator obtained Newton's efficiency higher than that of pneumatic separator closed type and showed a better degree of separation. Cenospheres recovery, particle distribution and visualisation of both underflow and overflow product using Scanning Electron Microscopy (SEM) were also performed to comprehensively depict the separation performance of both dry separation processes. It was found that micron separator's Newton's efficiency tendency is in line with the estimate, showing that dry separation process achieves a degree of separation as high as the commonly used technology which is wet separation process..
440. Sayo MORIYAMA, Keiko SASAKI, Hitoshi YOSHIZAKA, Tsuyoshi HIRAJIMA, Effect of Calcination Temperature During Production of Magnesium Oxide on Borate Sorption, Proc. 4th International Boron Symposium, 477-486, 2009.12.
441. Keiko SASAKI, Hitoshi YOSHIZAKA, Sayo MORIYAMA, Tsuyoshi HIRAJIMA, Mechanism of Immobilization of Borate on Magnesium Oxide, Proc. 4th International Boron Symposium, 455-466, 2009.12.
442. Atsunori TAYAOKA, Satoru NAGAO, Tsuyoshi HIRAJIMA, Keiko SASAKI, Recovery of Cu and PVC from the Tailings of Covered Electric Wire Using the Air Classification, Proc. International Symposium on Earth Science and Technology , 555-558, 2009.12.
443. Ahmad T. YULIANSYAH, Tsuyoshi HIRAJIMA, Satoshi KUMAGAI, Keiko SASAKI, Decomposition Behavior of Oil Palm Fiber and Shell under Hydrothermal Treatment, Proc. International Symposium on Earth Science and Technology , 345-350, 2009.12.
444. Takehito EMOTO, Tsuyoshi HIRAJIMA, Satoshi KUMAGAI, Moriyasu NONAKA, Keiko SASAKI, Hydrothermal Treatment of Acacia Mangium in a Hot-Compressed Water Using a Fast Heating Device, Proc. International Symposium on Earth Science and Technology , 341-344, 2009.12.
445. Shotaro KAWADA, Tsuyoshi HIRAJIMA, Moriyasu NONAKA, Satoshi KUMAGAI, Keiko SASAKI, Decomposition of Fructose into 5-Hydroxymethylfurfural Using a Continuous Flow Type Hydrothermal Equipment, Proc. International Symposium on Earth Science and Technology , 333-336, 2009.12.
446. Shuhei OKABE, Tsuyoshi HIRAJIMA, Moriyasu NONAKA, Satoshi KUMAGAI, Keiko SASAKI, Characterization of Moso-Bamboo Upgraded by Hydrothermal Treatment, Proc. International Symposium on Earth Science and Technology, 337-340, 2009.12.
447. Hitoshi YOSHIZAKA, Keiko SASAKI, Sayo MORIYAMA, Tsuyoshi HIRAJIMA, Reaction Mechanism of Boron with Magnesium Oxide in the Aqueous Phase, Proc. International Symposium on Earth Science and Technology, 477-486, 2009.12.
448. Koichiro TAKATSUGI, Keiko SASAKI, Tsuyoshi HIRAJIMA, Toshihiko OHNUKI, Olli H. TUOVINEN, Characterization of Secondary Formed Minerals in Bioleaching of Enargite by As-Adapted Acidithiobacillus ferrooxidans, Proc. International Symposium on Earth Science and Technology, 355-358, 2009.12.
449. Keiko SASAKI, Akihiro IMAI, Koichiro TAKATSUGI, Tsuyoshi HIRAJIMA, Bioleaching of Bornite (Cu5FeS4) by Acidithiobacillus ferrooxidans in the Presence of Pyrite, Proc. International Symposium on Earth Science and Technology, 551-553, 2009.12.
450. Keiko SASAKI, Naoyuki FUKUMOTO, Sayo MORIYAMA, Tsuyoshi HIRAJIMA, Sorption of Fluoride Ions on Magnesium Oxides Calcined at Different Temperatures, Proc. International Symposium on Earth Science and Technology, 545-562, 2009.12.
451. Keiko Sasaki, Koichiro Takatsugi, Tsuyoshi Hirajima, Naofumi Kozai, Toshihiko Ohnuki, Olli H. Tuovinen, Bioleaching of enargite by arsenic-tolerant Acidithiobacillus ferrooxidans, 18th International Biohydrometallurgy Symposium, IBS 2009 Biohydrometallurgy 2009 A Meeting Point between Microbial Ecology, Metal Recovery Processes and Environmental Remediation - Selected, peer rev. papers 18th Int. Biohydrometallurgy Symp., IBS 2009, 10.4028/www.scientific.net/AMR.71-73.485, 485-488, 2009.12, Acidithiobacillus ferrooxidans was acclimatized to 1000 mg/L arsenic(V) and then used for the bioleaching of enargite (Cu3AsS4) at pH 2. Secondary minerals formed during the bioleaching of enargite were characterized by X-ray diffraction, FT- infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Oxidative dissolution of enargite resulted in the formation of elemental sulfur, arsenate and oxidized sulfur species including jarosites and possibly also schwertmannite at pH 2..
452. Keiko Sasaki, T. Kaseyama, Tsuyoshi Hirajima, Selective sorption of Ce3+ over La3+ ions on biogenic manganese oxides, 18th International Biohydrometallurgy Symposium, IBS 2009 Biohydrometallurgy 2009 A Meeting Point between Microbial Ecology, Metal Recovery Processes and Environmental Remediation - Selected, peer rev. papers 18th Int. Biohydrometallurgy Symp., IBS 2009, 10.4028/www.scientific.net/AMR.71-73.633, 633-636, 2009.12, Unique properties of biogenic Mn oxides were applied to a fundamental study of separation and recovery of rare earth elements. Selective sorption of Ce3+ over La3+ ions was achieved at neutral pH values using biogenic Mn oxides produced by Paraconiothyrium sp. WL-2 strain. The selective coefficient for Ce3+ (αCe) was much greater with biogenic and synthetic Mn oxides than those for La3+La). Ce3+ ions were oxidized to CeO2 by Mn(III, IV) in Mn oxides under anaerobic conditions resulting in the release of Mn2+ ions, while La3+ ions were sorbed without a redox reaction. With an increase in coexisting La3+ ions, sorption of Ce3+ on both Mn oxides was significantly suppressed, especially with synthetic Mn oxides. The edges of the structure are competitive sites because of fewer numbers of vacant sites in synthetic Mn oxide layers. The preferential sorption on the edge sites of Mn oxides is in the order of La3+ > Ce3+. These phenomena can be expanded to separation and recovery of other rare earth elements from natural and anthropogenic sources..
453. Keiko SASAKI, Takuya KASEYAMA, Tsuyoshi HIRAJIMA, Selective sorption of cobalt over nickel using biogenic manganese oxides, Materials Transactions, Vol. 50, pp.2643-2648, 2009, 2009.11.
454. Mohsen Farahat, Tsuyoshi Hirajima, Keiko Sasaki, Katsumi Doi, Adhesion of Escherichia coli onto quartz, hematite and corundum
Extended DLVO theory and flotation behavior, Colloids and Surfaces B: Biointerfaces, 10.1016/j.colsurfb.2009.07.009, 74, 1, 140-149, 2009.11, The adhesion of Escherichia coli onto quartz, hematite and corundum was experimentally investigated. A strain of E. coli was used that had the genes for expressing protein for silica precipitation. The maximum cell adhesion was observed at pH <4.3 for quartz and at pH 4.5-8.5 for corundum. For hematite, cell adhesion remained low at all pH values. The microbe-mineral adhesion was assessed by the extended DLVO theory approach. The essential parameters for calculation of microbe-mineral interaction energy (Hamaker constants and acid-base components) were experimentally determined. The extended DLVO approach could be used to explain the results of the adhesion experiments. The effect of E. coli on the floatability of three oxide minerals was determined and the results showed that E. coli can act as a selective collector for quartz at acidic pH values, with 90% of the quartz floated at 1.5 × 109 cells/ml. However, only 9% hematite and 30% corundum could be floated under similar conditions. By using E. coli and no reagents, it was possible to separate quartz from a hematite-quartz mixture with Newton's efficiency of 0.70. Removal of quartz from the corundum mixture was achieved by E. coli with Newton's efficiency of 0.62..
455. Keiko Sasaki, Takuya Kaseyama, Tsuyoshi Hirajima, Selective sorption of Co2+ over Ni2+ using biogenic manganese oxides, Materials Transactions, 10.2320/matertrans.M-M2009821, 50, 11, 2643-2648, 2009.11, Preferential sorption of Co2+ ions over Ni2+ ions was achieved using biogenic Mn oxides produced by the Mn-oxidizing fungus Paraconiothyrium sp. WL-2 strain with a maximum selectivity coefficient (αCo) of 18. The selective sorption was based on different sorption mechanism for Co2+ and Ni2+ and unique properties of biogenic Mn oxides. The octahedral Co2+ ions occupy vacancies of central metal sites and edge sites in the octahedral Mn oxide unit structures of biogenic Mn oxides, where they are immobilized by oxidation to CoOOH by Mn(III). In contrast, Ni2+ ions are sorbed primarily on layer edges at circumneutral pHs without oxidation. Selective sorption of Co2+ over Ni2+ on the biogenic Mn oxides results from more vacant sites, higher Mn(III) contents, and larger specific surface areas compared to synthetic Mn oxides..
456. K. SASAKI, K. TAKATSUGI, T. HIRAJIMA, N. KOZAI, T. OHNUKI, O. H. TUOVINEN, Bioleaching of Enargite by Arsenic-torelant Acidithiobacillus ferrooxidans, Advanced Materials Research, 71-73, 485-488, 2009.10.
457. K. SASAKI, T. KASEYAMA, T. HIRAJIMA, Selective Sorption of Ce3+ over La3+ ion on Biogenic Manganese Oxides, Advanced Materials Research, 71-73, 633-636, 2009.10.
458. Keiko SASAKI, Koichiro TAKATSUGI, Tsuyoshi HIRAJIMA, Naofumi KZAI, Toshihiko OHNUKI, Olli H. TUOVINEN, Bioleaching of Enargite by Arsenic- Tolerant Acidithiobacillus ferrooxidans, 18th Proc. International Symp. Biohydrometallurgy 2009. , 485-488, 2009.09.
459. Keiko SASAKI, Takuya KASEYAMA, Tsuyoshi HIRAJIMA, Selective Sorption of Ce3+ over La3+ ion on Biogenic Manganese Oxides, 18th Proc. International Symp. Biohydrometallurgy 2009., 633-636, 2009.09.
460. K. Sasaki, H. Nakano, W. Wilopo, Y. Miura, T. Hirajima, Sorption and speciation of arsenic by zero-valent iron, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2008.10.033, 347, 1-3, 8-17, 2009.09, Sorption and speciation of arsenic in groundwater remediation using zero-valent iron (ZVI) was investigated by batch and column experiments. In batch tests, arsenite was oxidized to arsenate which was favorably immobilized by co-precipitation with Fe(III)-bearing compounds as corrosion products, leading to the dominant surface species of As(V). In column materials after introducing influent with arsenite for 22 pore volumes(pvs), As(III) was predominant on the surface of ZVI in all segments of column, while intense oxidation of arsenite to arsenate was observed especially near the inlet. It is considered that the surface of ZVI granules was already uniformed and corrosion products are the most accumulated on ZVI granules near the inlet because ZVI has been contacted with high concentrations of arsenite for the longest time in the most bottom parts. This was also supported by the experimental results of XPS that relative intensity of O 1s peak assigned to oxide was the largest in the most bottom segment. Also XPS results revealed that arsenic was immobilized on ZVI granules mainly as arsenite and to a lesser extent arsenate. These observations suggest that the retention mechanism is primarily sorption rather than reduction. The results of geochemical calculations along with the SEM-EDX suggest that arsenite and arsenate were co-precipitated with mainly Fe(III)-bearing minerals and carbonates..
461. Treatment of Heavy Metals in a Constructed Wetland, Kaminokuni, Hokkaido
-Role of Microorganisms in Immobilization of Heavy Metals in Wetland Soils-.
462. Treatment of Heavy Metals in a Constructed Wetland, Kaminokuni, Hokkaido
-Accumulation of Heavy Metals in Emergent Vegetations-.
463. Mohsen Farahat, Tsuyoshi Hirajima, Keiko Sasaki , Katsumi Doi, Adhesion of Escherichia coli onto Quartz, Hematite and Corundum: Extended DLVO Theory and Flotation Behavior, Colloids and Surfaces B: Biointerfaces, Vol. 74, pp.140-149, 2009, 2009.07.
464. Robert S. BOWMAN, Keiko Sasaki, Tomohiro URATA, Sorption of Fluoride by Modified Zeolites, Proc. 10th International Conference of Biogeochemical Trace Elements 2009, CDR, 2009.07.
465. Keiko SASAKI, Generation and Prevention of Acid Mine Drainages from Mine Tailings, Proc. 2nd International Symposium of Novel Carbon Resource Science, Earth Resource Science and Technology, IV5-IV11 , 2009.03.
466. Keiko Sasaki, Eljamal OSAMA, Tosao HOSOKAWA, Modeling of Solute Transport and Biological Sulfate Reduction Using of Low Cost Electron Donor, Journal of Environmental Geology, 2009, 2, Vol. 56, , pp.1605-1613, 2009.02.
467. Keiko Sasaki, Yousuke Nakamuta, Tsuyoshi Hirajima, Olli H. Tuovinen, Raman characterization of secondary minerals formed during chalcopyrite leaching with Acidithiobacillus ferrooxidans, Hydrometallurgy, Vol. 95, (2009) pp.153-158., 2009.01.
468. K. Sasaki, Y. Nakamuta, T. Hirajima, O. H. Tuovinen, Raman characterization of secondary minerals formed during chalcopyrite leaching with Acidithiobacillus ferrooxidans, Hydrometallurgy, 10.1016/j.hydromet.2008.05.009, 95, 1-2, 153-158, 2009.01, Chalcopyrite passivation greatly reduces the yields from leaching and bioleaching but the problem has not been successfully resolved. Passivation involves the formation of a layer of secondary minerals on chalcopyrite surface, which becomes a diffusion barrier to fluxes of reactants and products. This study aims to identify secondary minerals formed during chalcopyrite passivation in the presence of iron- and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans) in mineral salts solution. The minerals were characterized with X-ray diffraction, Fourier transform-infrared spectroscopy, and Raman spectroscopy. Potassium jarosite was the initial product covering chalcopyrite grains, followed by the formation of ammonio-jarosite. Covellite and elemental sulfur were also detected in the passivation layer. The results suggest that passivation may be reduced by controlling jarosite precipitation and prior acclimatization of bacteria to oxidize CuS and elemental S in the presence of ferrous and ferric iron..
469. Anggoro Tri Mursito, Tsuyoshi Hirajima and Keiko Ssasaki, CATALYTIC EFFECTS ON PRODUCTS OF ALKALINE HYDROTHERMAL TREATMENT
OF RAW PEAT, Proc. International Symposium on Earth Science and Technology 2008, pp.35-42, 2008.12.
470. Ahmad T. Yuliansyah, Tsuyoshi Hirajima, Moriyasu Nonaka and Keiko Sasaki, HYDROTHERMAL TREATMENT OF OIL PALM FIBER AND SHELLCHARACTERIZATION
OF SOLID PRODUCTS, Proc. International Symposium on Earth Science and Technology 2008, pp.129-134, 2008.12.
471. Takuya Kaseyama, Keiko Sasaki and Tsuyoshi Hirajima, SORPTION MECHANISM OF Co2+ AND Ni2+ IONS ON THE BIOGENIC MN OXIDE IN
THE BINARY SOLUTE SYSTEM, Proc. International Symposium on Earth Science and Technology 2008, pp.157-164, 2008.12.
472. Tomohiro Urata, Keiko Sasaki, Tsuyoshi Hirajima and Robert S. Bowman, MECHANISM IN SORPTION OF FLUORIDE IONS ONTO SEVERAL TYPES OF
NATURAL ZEOLITES, Proc. International Symposium on Earth Science and Technology 2008, pp.165-172, 2008.12.
473. Hitoshi Takamori, Keiko Sasaki, Hitoshi Yoshizaka and Tsuyoshi Hirajima, ROLE OF WOOD-CHIPS IN PERMEABLE REACTIVE BARRIERS FOR REMOVAL OF
BORATE IN GROUNDWATERS, International Symposium on Earth Science and Technology 2008, pp.181-188, 2008.12.
474. Tsuyoshi Hirajima, Yuki Aiba, Mohsen Farahat, Keiko Sasaki, Takehiko Tsuruta and Katsumi Doi, FLOCCULATION OF QUARTZ BY MICROORGANISMS, Proc. International Symposium on Earth Science and Technology 2008, pp.189-194, 2008.12.
475. Syoutaro Kawada, Tsuyoshi Hirajima, Moriyasu Nonaka and Keiko Sasaki, UPGRADING OF BIOMASS USING A CIRCULATIVE HYDROTHERMAL EQUIPMENT, Proc. International Symposium on Earth Science and Technology 2008, pp.201-206, 2008.12.
476. Mohsen Farahat, Tsuyoshi Hirajima and Keiko Sasaki, ADSORPTION OF FERROPLASMA ACIDIPHILUM ONTO PYRITE AND ITS AFFECT ON
THE FLOTATION OF THE MINERAL, Proc. International Symposium on Earth Science and Technology 2008, pp.389-396, 2008.12.
477. Satoru Nagao, Atsunori Tayaoka, Tsuyoshi Hirajima and Keiko Sasaki, DEVELOPMENT OF ON-LINE MONITORING AND CONTROL SYSTEM FOR AIR
CLASSIFICATION, Proc. International Symposium on Earth Science and Technology 2008, pp.397-402, 2008.12.
478. Keiko Sasaki, Koichiro Takatsugi, Kazuhiro Ishikura and Tsuyoshi Hirajima, SURFACE CHARACTERISTICS OF As-BEARING COPPER SULFIDES OXIDIZED
AT DIFFERENT pHs, Proc. International Symposium on Earth Science and Technology 2008, pp.687-694, 2008.12.
479. K. Sasaki, H. Nakano, W. Wilopo, Y. Miura, T. Hirajima, Sorption and speciation of arsenic by zero-valent iron, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 347, 8-17, 2009, 2008.12.
480. Wahyu Wilopo, Keiko Sasaki, Tsuyoshi Hirajima, Toshiro Yamanaka, Immobilization of Arsenic and Manganese in Contaminated Groundwater by Permeable Reactive Barrier Using Zero Valence Iron and Sheep Manure, Materials Transactions, Vo. 49, No. 10, pp. 2265-2274, 2008.10.
481. W. WILOPO, K. SASAKI, T. HIRAJIMA, Identification of Sulfate- and Arsenate-Reducing Bacteria in Sheep Manure As Permeable Reactive Materials after Arsenic Immobilization in Groundwater., Materials Transactions, Vol. 49, No. 10, pp.2275-2282, 2008.10.
482. Wahyu Wilopo, Keiko Sasaki, Tsuyoshi Hirajima, Identification of sulfate- And arsenate-reducing bacteria in sheep manure as permeable reactive materials after arsenic immobilization in groundwater, Materials Transactions, 10.2320/matertrans.M-MRA2008826, 49, 10, 2275-2282, 2008.10, Permeable reactive barriers (PRBs) column tests were performed to investigate the contribution of anaerobic microbial community in sheep manure on the removal of As from groundwater. The column was packed with zero valent iron (ZVI), sheep manure, compost, wood chips, glass beads and gravels. All materials were sterilized except for sheep manure that contains anaerobic bacteria. Decrease in sulfate concentration was observed at the maximum rate of 0.26 mmol dm-3 day-1. In addition, the sulfur isotopic ratio of δ34S increased from the influent (-4.3%o) to the effluent (0.2%o), suggesting that there was sulfate-reducing activity in the microbial community. Arsenate was more effectively immobilized on ZVI than arsenite. Bacterial community analysis using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) on 16S rRNA sequences suggested that majorities of bacteria were several Clostridium species and one species of Proteobacteria, Geobacter metallireducens GS-15, independently of PRBs column heights. Some of them might have contributed to the removal of arsenic..
483. Wahyu Wilopo, Keiko Sasaki, Tsuyoshi Hirajima, Toshiro Yamanaka, Immobilization of arsenic and manganese in contaminated groundwater by permeable reactive barriers using zero valent iron and sheep manure, Materials Transactions, 10.2320/matertrans.M-MRA2008827, 49, 10, 2265-2274, 2008.10, A permeable reactive barriers (PRBs) column test was carried out to remove arsenic (As) and manganese (Mn) from groundwater using zero valent iron (ZVI), sheep manure, compost and woodchips as reactive materials. Arsenic was mainly immobilized through sorption and co-precipitation with iron-bearing minerals, and also possibly precipitation as FeAsO4. The presence of sulfate-reducing bacteria (SRB) in the inoculated column was suggested by decrease of sulfate concentrations and increase of δ34S in the effluent. Arsenic was more effective to immobilize in the inoculated than in the sterilized column due to co-precipitation with sulfides formed by reduction of sulfate in addition sorption and/or co-precipitation with carbonates. The Mn was mainly immobilized through adsorption onto compost and ZVI, and partly by precipitation as carbonates. Manganese was more effectively immobilized in the sterilized than in the inoculated column. Since compost is biodegraded, the capability of compost to immobilize Mn2+ decreased in the inoculated column. The result demonstrates that As is more effective to immobilize using mixture of sheep manure with ZVI than only ZVI as reactive materials in PRBs..
484. Olia V. Karnachuk, Keiko Sasaki, Anna L. Gerasimchuk, Olga Sukhanova, Denis A. Ivasenko, Anna H. Kaksonen, Jaakko A. Puhakka, Olli H.Tuovinen, Precipitation of Cu-sulfides by Copper-tolerant Desulfovibrio Isolates, Geomicrobiology Journal, Vol. 25, pp. 1-8, 2008.07.
485. KEIKO SASAKI, SHUNSUKE NUKINA, WAHYU WILOPO, TSUYOSHI HIRAJIMA, Treatment of arsenate in acid mine drainage by a permeable reactive barrier bearing granulated blast furnace slag: column study, Geochimica Cosmochimica Acta, 72, 12, A824, 2008.07.
486. Olia V. Karnachuk, Keiko Sasaki, Anna L. Gerasimchuk, Olga Sukhanova, Denis A. Ivasenko, Anna H. Kaksonen, Jaakko A. Puhakka, Olli H. Tuovinen, Precipitation of Cu-sulfides by copper-tolerant Desulfovibrio isolates, Geomicrobiology Journal, 10.1080/01490450802153124, 25, 5, 219-227, 2008.07, The purpose of this work was to isolate Cu-tolerant sulfate-reducers that could be used to produce copper sulfides under pure culture conditions. Three sulfate-reducing bacteria were isolated from wastewater effluents of a zinc-smelter in the Urals and their tolerance to copper varied between 325 and 2600 mg Cu l-1. Analysis of 16S rRNA gene sequences placed the isolates in the genus Desulfovibrio. The isolates showed pronounced saccharolytic growth. Growing cultures precipitated Cu2+ as covellite (CuS) within less than a week. Extended incubation for 1 month lead to the formation of chalcocite (Cu2S) and chalcopyrite (CuFeS2)..
487. K. Sasaki, H. Takamori, H. Yoshizaka, T. Hirajima, SORPTION OF BORIC ACID ON MAGNESIUM OXIDE IN PERMEABLE REACTIVE BARRIERS, Proc. the 5th International Conference of Interface Against Pollution, 2008.06.
488. K. Sasaki, H. Nakano, W. Wilopo, T. Hirajima, SPECIATION OF ARSENIC IN TREATMENT OF GROUNDWATERS SPIKED WITH ARSENITE USING PERMEABLE REACTIVE MATERIALS, Proc. the 5th International Conference of Interface Against Pollution, 2008.06.
489. T. Tsuruta, Y. Aiba, T. Hirajima, and K. Sasaki, Biosorption of some heavy metals using microorganisms, Proc. the 5th of international Conference of Interface Against Pollution, 2008.06.
490. KEIKO SASAKI, DAVID W. BLOWES, CAROL J. PTACEK, Spectroscopic study of precipitates formed during removal of selenium from mine drainage spiked with selenate using permeable reactive materials, Geochemical Journal, Vol. 42, pp. 283-294, 2008.06.
491. K. Sasaki, D. W. Blowes, C. J. Ptacek, W. D. Gould, Immobilization of Se(VI) in mine drainage by permeable reactive barriers
column performance, Applied Geochemistry, 10.1016/j.apgeochem.2007.08.007, 23, 5, 1012-1022, 2008.05, The potential for immobilization of Se in mine drainage water using a permeable reactive barrier was investigated by a column study, in which the reactive components were zero valent Fe, municipal leaf compost, sawdust, and wood chips. These components were mixed with silica sand and gravel. Trace amounts of creek sediment were added to serve as a source of anaerobic bacteria. The influent concentration (40 mg L-1) of SeO42 - decreased to less than 2 mg L-1 within one week and to less than 0.014 mg L-1 within 1 month during passage through the column. In the column, the concentrations of SO42 - also were reduced from 620 to 220 mg L-1. After 2 months, cell populations of SO42 --reducing bacteria, estimated using the MPN method, were in the range of 106-107 cells g-1. Isotopic analysis of S showed δ34S = -9.19‰ for the input solution, and δ34S = -4.69‰ for the output solution. This change in isotopic ratio is attributed to the preferential utilization of 32 SO42 - over 32 SO42 - by SO4-reducing bacteria in the column. Geochemical calculations indicate that SeO42 - is stable in the influent water, and that conditions within the column favour reduction of SeO42 - to metallic Se or SeO32 -, and the reduction of SO42 - to S2-..
492. Keiko Sasaki,Shunsuke Nukina,Wahyu Wilopo, Tsuyoshi Hirajima, Removal of arsenate in acid mine drainage by a permeable reactive barrier bearing granulated blast furnace slag: column study, Materials Transactions, Vol. 49(4), pp. 835-844, 2008.04.
493. K. Sasaki, H. Tachibana, Y. Ogawa, H. Konno, Oxidation of Mn(II) Ions in Model and Actual Manganese Drainages by a Fungus Closely Related to Phoma sp. like strain KY-1, Materials Transaction, Vol. 49(4), pp. 845-849, 2008.04.
494. Mohsen Farahat, Tsuyoshi Hirajima, Keiko Sasaki, Yuuki Aiba, Katsumi Doi, Adsorption of SIP E. coli onto quartz and its applications in froth flotation, Minerals Engineering, 10.1016/j.mineng.2007.10.019, 21, 5, 389-395, 2008.04, Zeta potential measurements of silica-induced protein (SIP) Escherichia coli and quartz showed that the former are positively charged under acidic condition and negatively charged under neutral and alkaline conditions, with an isoelectric point (IEP) at pH 4.5, while the quartz was always negatively charged. Adsorption experiments with bacteria cells on quartz were conducted under different conditions. The results show that at pH values lower than the IEP of the cells, more cells were adsorbed due to electrostatic forces. However, at pH > 4.5, the amount of adsorbed cells decreased as a result of electrostatic repulsion forces. Zeta potentials of quartz showed that at pH 2.5 a significant change in the surface chemistry of quartz occurred after bacterial treatment. The degree of this change was related to the initial SIP E. coli concentration; at 5 × 107 cells/ml the average zeta potential of biotreated quartz shifted from -30 mV to 0 mV and at higher concentrations the zeta potential shifted to the positive direction and reached a similar value to that of the bacterial cells. SIP E. coli showed hydrophobic properties at pH lower than the IEP, with approximately 60% of the cells moving to the organic phase from aqueous phase. Bioflotation of quartz using SIP E. coli alone at pH 2.5 gave approximately 60% recovery because at this pH more bacteria adsorb onto the quartz surface and the bacterial surface is hydrophobic. In anionic flotation of quartz using sodium dodecyl sulfate, SIP E. coli cells act as a surface modifier, with an increase in flotation recovery from 28% to 85%. This is because the bacterial cells confer hydrophobic properties to the quartz and the biotreated quartz is positively charged, so a large amount of the collector was adsorbed and the recovery increased..
495. Keiko Sasaki, Hideki Tachibana, Yuuki Ogawa, Hidetaka Konno, Optimum pH for oxidation of Mn(II) ions in model and actual manganese drainages by a Mn-oxidizing fungus, Phoma sp. strain KY-1, Materials Transactions, 10.2320/matertrans.M-MRA2008802, 49, 4, 845-849, 2008.04, A Mn-oxidizing fungus, Phoma sp. strain KY-1, showed a Mn-oxidizing activity of more than 1.82 mol m-3 of Mn(II) at an optimum pH 6.8. Controlling the pH at between 6.5 and 7.3 was necessary for fungal oxidation of Mn(II). This is probably due to inactivation of the Mn-oxidizing enzyme by decrease in pH during the reaction. Carbon fiber was found to catalyze the oxidation of Mn(II), most significantly under more unfavorable conditions such as high Mn concentrations, coexisting inhibitive components, or lacking nutrients. Examinations of fungus used for actual Mn-rich mine drainage containing more than 1.46 mol m-3 of Mn showed that organic nourishments and pH-buffering agents are both essential to obtain acceptable Mn removal rates and that the time required to attain the 10 mg dm-3 (0.182 mol m-3), which is the maximum acceptable concentration of Mn in discharged wastewater in Japan, was about 170h in the presence of carbon fiber..
496. Keiko Sasaki, Shunsuke Nukina, Wahyu Wilopo, Tsuyoshi Hirajima, Removal of arsenate in acid mine drainage by a permeable reactive barrier bearing granulated blast furnace slag
Column study, Materials Transactions, 10.2320/matertrans.M-MRA2008801, 49, 4, 835-844, 2008.04, Immobilization of arsenate in groundwater impacted by acid mine drainage was investigated using a permeable reactive barrier (PRB) column bearing granulated blast furnace slag (GBFS) to compare with iron granules which are commonly used. Sorption capacity of arsenate onto the GBFS was quite lower than iron granules in the amount of sorbed arsenate per unit surface area of sorbents (mmol/m2) at the equilibrium, Q′, in two orders of magnitude in batch tests, however, the amount of sorbed arsenate per unit amount of sorbents (mmol/kg) at the equilibrium, Q, were comparative to each other, because of much higher porosity in the GBFS. Results of column performance showed that 15 mg/L of As was decreased to be less than 0.4 mg/L for more than 18 pore volumes (pv) in the GBFS-PRB by sorption, co-precipitation and presumably formation of hydrated calcium arsenate, and less than 0.04 mg/L for more than 17pv in the iron bearing PRB probably by co-precipitation with iron (oxyhydro)oxides. Additionally 15 mg/L of Mn2+ ions was also decreased to less than 0.3 mg/L and 0.03 mg/L, respectively, in iron bearing and the GBFS bearing PRB columns, probably caused by sorption and precipitation of oxides and carbonates. The GBFS has advantages to compensate its low reactivity with high porosity, to facilitate the industrial handling with low density, and to utilize industrial wastes for more valuable applications, emphasizing a potential of alternative reactive materials instead of iron granules in PRB for immobilization of arsenic and manganese in acid mine drainage..
497. Keiko Sasaki, Minoru Matsuda, Tomohiro Urata, Tsuyoshi Hirajima, Hidetaka Konno, Sorption of Co2+ ions on the biogenic Mn oxide produced by a Mn-oxidizing fungus, Paraconiothyrium sp. WL-2, Materials Transactions, 10.2320/matertrans.M-MRA2007888, 49, 3, 605-611, 2008.03, A Paraconiothyrium sp. WL-2 of Mn-oxidizing fungus is highly tolerant to Mn2+ ions, and capable of oxidizing more than 380 mg dm-3 of Mn2+ ions, leading to the formation of a large amount of insoluble Mn(III, IV) oxides. The biogenic Mn oxides were characterized by X-ray diffraction, FT-Infrared spectroscopy, elemental analysis, measurement of specific surface area, scanning electron microscopy, and measurement of zeta potential, in comparison with the synthetic Mn oxides. It was found that the biogenic Mn oxide is poorly crystalized birnessite, with higher porosity and much more weakly bounded Mn(II) on the surface than the synthetic Mn oxide. Cobalt(II) ions were sorbed and incorporated as Co(III) into the structure of the biogenic Mn oxide. Sorption efficiency in the biogenic Mn oxide was 5.6 times as high as that in the synthetic ones. Relation of the relased Mn 2+ ions to the immobilized Co suggested that Mn(IV) is preferentially used as oxidants over Mn(III) in the biogenic Mn oxide, and emphasized that the existence of Mn(III) in the biogenic Mn oxide activates the geochemical cycles of Mn and the other involved elements in environments..
498. K. Sasaki, D. W. Blowes, C. J. Ptacek, Immobilization of selenate in mine drainage by permeable reactive barriers: column performance., Applied Geochemistry, Vol. 23, No. 5, pp. 1012-1022, 2008.02.
499. K. Sasaki, M. Matsuda, T. Urata, T. Hirajima, H. Konno, Sorption of Co2+ ions on the biogenic Mn deposits by a Mn-oxidizing fungus,Paraconiothyrium sp.-like strain WL-2, Materials Transaction, Vol. 49(3), pp. 605-611, 2008.01.
500. Keiko Sasaki, David W. Blowes, Carol J. Ptacek, Spectroscopic study of precipitates formed during removal of selenium from mine drainage spiked with selenate using permeable reactive materials, GEOCHEMICAL JOURNAL, 10.2343/geochemj.42.283, 42, 3, 283-294, 2008.01, The potential for Se removal from mine drainage water using permeable reactive materials was evaluated by a laboratory column experiment. The column materials, organic carbon and zero valence iron (ZVI), were exposed to mine drainage containing 630 mg L-1 SO42-. The influent water was spiked with 40 mg L-1 Se(VI) to assess the potential for Se removal. This high Se(VI) concentration was selected to ensure that there would be a sufficient mass of Se-bearing reaction products available for mineralogical characterization. The experiment was conducted in an anaerobic chamber to replicate the anaerobic conditions that prevail in permeable reactive barrier systems. After loading 10.8 pore volumes of input solution, the column effluent contained <0.002 mg L-1 Se and <300 mg L-1 SO4 2-. After the column experiments was complete the reactive materials were sampled in the anaerobic chamber and examined using scanning electron microscopy (SEM) coupled with energy dispersion X-ray analysis (SEM-EDAX), X-ray photoelectron spectroscopy (XPS) and by Raman spectroscopy. Sulfate was reduced to sulfide and elemental sulfur, which accumulated on the surfaces of the column materials. Se-bearing precipitates were observed at the base of column. Scanning electron microscopy (SEM) showed the presence of elemental Se, suggesting that Se(VI) was partly reduced to metallic Se(0). The XPS results revealed that selenate was reduced mainly to iron selenide (FeSe and/or FeSe2) on the surface of the column substances. These observations suggest that both chemical reduction and biologically mediated reduction of Se(VI) occurred..
501. H. Takamori, K. Sasaki, T. Hirajima, Sorption of boric acid onto woody biomass as reactive materials in permeable reactive barriers., Proc.5th International Workshop on Earth Science and Technology, 205-212, 2007.12.
502. K. Sasaki, T. Urata, T. Hirajima, Sorption of fluoride ions onto agglomerated magnesium oxides as reactive materials in permeable reactive barrier. , Proc.5th International Workshop on Earth Science and Technology, 495-500, 2007.12.
503. W. WILOPO, K. SASAKI, T. HIRAJIMA:, Effect of Bacteria in Sheep Manure on Arsenic Removal from Groundwater by Permeable Reactive Barriers., Proc.5th International Workshop on Earth Science and Technology, 197-204, 2007.12.
504. K. Sasaki, Y. Nakamuta, T. Hirajima, Bacterial leaching of arsenic-rich copper sulfide ores with Acidithiobacillus ferrooxidans. , Proc.5th International Workshop on Earth Science and Technology, 507-514, 2007.12.
505. Tsuyoshi Hirajima, Yuji OOSAKO, Moriyasu Nonaka, Keiko Sasaki, Takashi ANDO, Recovery of Hollow and Spherical Particles from Fly Ash Using Dry Separation Process, Proc.5th International Workshop on Earth Science and Technology, 213-218, 2007.12.
506. Tsuyoshi HIRAJIMA, Yuki AIBA, Mohsen FARAHAT, Keiko SASAKI and Katsumi DOI, ADSORPTION OF SIP E.COLI ONTO QUARTZ: APPLICATIONS IN THE FLOCCULATION OF MINERALS, Proc.5th International Workshop on Earth Science and Technology, 501-506, 2007.12.
507. Anggoro Tri MURSITO, Tsuyoshi HIRAJIMA, Moriyasu NONAKA and Keiko SASAKI, FUNDAMENTAL STUDY ON PRODUCTION OF PEAT FUEL USING HYDROTHERMAL TREATMENT., Proc.5th International Workshop on Earth Science and Technology, 107-114, 2007.12.
508. Jumpei YABUKI, Tsuyoshi HIRAJIMA, Moriyasu NONAKA and Keiko SASAKI, UPGRADING MECHANISM OF MOSO-BAMBOO BY HYDROTHERMAL TREATMENT. , Proc.5th International Workshop on Earth Science and Technology, 115-122, 2007.12.
509. Mohsen Frahat, Tsuyoshi Hirajima, Keiko Sasaki, Yuuki Aiba, Katsumi Doi, Adsorption of SIP E. coli onto quartz and its applications in froth flotation, Minerals Engineering, Vol.21(5), pp.389-395, 2007.12.
510. Keiko Sasaki, M. Matsuda, T. Urata, Tsuyoshi Hirajima, H. Konno, Sorption of Co ions on biogenic Mn oxides procuced by a Mn-oxidizing fungus, Paraconiothyrium sp.-like strain, 17th International Biohydrometallurgy Symposium, IBS 2007 Biohydrometallurgy From the Single Cell to the Environment, 607-610, 2007.12, Sorption of Co(II) on the biogenic Mn oxide produced by a Paraconiothyrium sp.-like strain was investigated. The biogenic Mn oxide, which was characterized to be poorly crystalline birnessite (Na4Mn(III) 6Mn(IV)8O27 • 9H2O) bearing Mn(III) and Mn(lV) in the structure, showed approximately 6.0-fold higher efficiency for Co(II) sorption than a synthetic Mn oxide. XP-spectra of Co 2p for the biogenic and synthetic Mn oxides after Co(II) sorption indicate that Co was immobilized as Co(III) on the surface of Mn oxides, clearly suggesting that redox reaction occurs between Co(II) ions and each Mn oxides. The Co(II) ions would be initially sorbed on the vacant sites of the surface of biogenic Mn oxide, and then oxidized to Co(III) by neighbor Mn(III/IV) atoms to release Mn(II). For the synthetic Mn oxide, release of Mn(II) was negligibly small because the oxidant is only Mn(IV) in ramsdellite (γ-MnO 2). The Mn(II) release from the biogenic Mn oxide during Co(II) adsorption would be not only from weakly bounded Mn(II), but also from redox reaction between Mn(III/IV) and Co(II) ions..
511. Jonathan P. Gramp, Jerry M. Bigham, Keiko Sasaki, and Olli H. Tuovinen, Formation of Ni- and Zn-sulfides in cultures of sulfate-reducing bacteria., J. Geomicrobiology, Vol, 24, pp. 2-7, 2007.11.
512. Jonathan P. Gramp, Jerry M. Bigham, Keiko Sasaki, Olli H. Tuovinen, Formation of Ni- and Zn-Sulfides in cultures of sulfate-reducing bacteria, Geomicrobiology Journal, 10.1080/01490450701758239, 24, 7-8, 609-614, 2007.10, The purpose of this study was to characterize Ni- and Zn-sulfides precipitated in sulfate-reducing bacterial cultures. Fe-free media containing 58 mM SO42- were amended with Ni and Zn chloride followed by inoculation. Precipitates were sampled from cultures after two weeks of incubation at 22, 45, and 60°C. Abiotic controls were prepared by reacting bacteria-free liquid media with Na2S solutions under otherwise identical conditions. Precipitates were collected anaerobically, freeze-dried and analyzed by x-ray diffraction (XRD), scanning electron microscopy, and for total Ni, Zn, and S. In Ni-containing media, biogenic sulfide precipitates were mostly heazelwoodite (Ni3S2), whereas abiotic precipitates were mixed heazelwoodite and vaesite (NiS2). The biogenic Ni-precipitates were better crystalline than the corresponding abiotic samples. Sphalerite (ZnS) was identified by XRD in precipitates sampled from Zn-containing media. Scanning electron microscopy revealed disordered morphological features for the sulfides, which occurred mostly as aggregates of fine particles in biogenic samples, whereas abiotic precipitates contained more plate- and needle-like structures..
513. K. Sasaki, M. Matsuda, T. Urata, T. Hirajima, H. Konno, Sorption of Co ions on biogenic Mn oxides produced by a Mn-oxidizing fungus, Paraconiothyrium sp.-like strain., Advanced Materials Research)., 20-21, 607-610, 2007.07.
514. Hidetaka KONNO, Keiko SASAKI, Yuuki OGAWA, Hideki TACHIBANA, Singular effect of carbon fibers on the oxidation of dissolved Mn(II) ions by a fungus closely related to Phoma sp., Materials Transactions, 48(1), 64-67, 2007.01.
515. Hidetaka Konno, Keiko Sasaki, Yuuki Ogawa, Hideki Tachibana, Singular effect of carbon fiber on the oxidation of dissolved Mn(II) ions by a fungus genetically related to phoma sp, Materials Transactions, 10.2320/matertrans.48.64, 48, 1, 64-67, 2007.01, Oxidation of Mn(II) ions in model drainages by a fungus genetically related to Phoma sp. was carried out in the presence of polyacrylonitrile-based carbon fiber, pitch-based carbon fibers formed at different heat treatment temperatures, and bamboo charcoal, aiming to understand the morphological effect of carbon materials on the microbiological activity of the manganese-oxidizing fungus. From the experimental results obtained so far, it was reasonably concluded that only carbon fiber accelerates the oxidation of dissolved Mn(II) ions by this fungus. When the carbon fiber shortened below certain length, the promoting effect was lost. The results strongly suggest that the shape of carbon, specifically the fibrous shape having flexibility, is a crucial factor in the promoting effect on the mansanese oxidation by the present fungus.
516. T. Hirajima, J. Yabuki, M. Nonaka, K. Sasaki, Characterization of Bamboo Upgrading by Hydrothermal Treatment., Proc. 4th International Workshop on Earth Science and Technology, 2006.12.
517. M. Farahat, T. Hirajima, Y. Aiba, Y. Fujino, K. Doi, Surface Modification of Quartz Using SIP Producing E. coli., Proc. 4th International Workshop on Earth Science and Technology, 2006.12.
518. K. SASAKI, H. NAKANO, Y. MIURA, T. HIRAJIMA, XPS Study on Characterization of Arsenic Immobilized in Abiotic Permeable Reactive Barrier (PRB) Treatment Using Zero Valence Iron (ZVI)., Proc. 4th International Workshop on Earth Science and Technology, 2006.12.
519. W. WILOPO, K. SASAKI, T. HIRAJIMA, Immobilization of As (III) and As (V) in Groundwater by Permeable Reactive Barriers Using Iron Granular and Cow Manures., Proc. 4th International Workshop on Earth Science and Technology, 2006.12.
520. K. SASAKI, M. MATSUDA, T. HIRAJIMA, Interaction of Co(II) Ions with the Biogenic Manganese Oxide Produced by Paraconiothyrium sp.-like Strain of Fungus., Proc. 4th International Workshop on Earth Science and Technology, 2006.12.
521. Jonathan P. Gramp, Keiko Sasaki, Jerry M. Bigham, Olia V. Karnachuk, Olli H. Tuovinen, Formation of covellite (CuS) under biological sulfate-reducing conditions, Geomicrobiology Journal, 10.1080/01490450600964383, 23, 8, 613-619, 2006.12, Sulfate-reducing bacteria (SRB) play a major role in the precipitation of metal sulfides in the environment. In this work, biogenic copper sulfide formation was examined in cultures of SRB and compared to chemically initiated Cu sulfide precipitation as a reference system. Mixed cultures of SRB were incubated at 22, 45, and 60°C in nutrient solutions that contained copper sulfate. Abiotic reference samples were produced by reacting uninoculated liquid media with Na2S solutions under otherwise identical conditions. Precipitates were collected anaerobically by centrifugation, frozen in liquid N2, and freeze-dried, followed by analysis using X-ray diffraction (XRD), X-ray fluorescence, and scanning electron microscopy. Covellite (CuS) was the only mineral found in the precipitates. Covellite was less crystalline in the biogenic precipitates than in the abiotic samples based on XRD peak widths and peak to background ratios. Poor crystallinity may be the result of slower precipitation rates in bacterial cultures as compared to the abiotic reference systems. Furthermore, bacterial cells may inhibit the nucleation steps that lead to crystal formation. Incubation at elevated temperatures improved the crystallinity of the biotic specimens..
522. Keishi Takano, Yasoo Itoh, Tagiru Ogino, Kunihiko Kurosawa, Keiko Sasaki, Phylogenetic analysis of manganese-oxidizing fungi isolated from manganese-rich aquatic environments in Hokkaido, Japan, Limnology, 10.1007/s10201-006-0177-x, 7, 3, 219-223, 2006.12, Three strains of Mn-oxidizing fungi were isolated from manganese-rich aquatic environments: sediment in a stream (Komanoyu) in Mori-machi and inflow to an artificial wetland in Kaminokuni-cho, Hokkaido, Japan. The characteristics of each strain were then established. Genetic analysis based on the ribosomal RNA (rRNA) gene was performed to clarify their classification. The sequences of the 18S rRNA and internal transcribed spacer (ITS1)-5.8S rRNA-ITS2 genes showed that all three strains are Ascomycetes. Based on its morphology, it seems probable that the KY-1 strain from Mori-machi belongs to the genus Phoma or Ampelomyces. The phylogenetic analysis indicates that this strain belongs to Phoma rather than Ampelomyces. Morphological identification of WL-1 and WL-2 strains from Kaminokuni-cho was impossible because of the lack of a sexual stage and specific organs. Phylogenetic analysis of the sequence in the ITS1-5.8S rRNA-ITS2 gene suggests that the WL-1 strain corresponds to Paraconyothyrium sporulosum and that WL-2 also belongs to the genus Paraconiothyrium. Because the ability to oxidize Mn has not been evaluated for most species of Phoma or Paraconiothyrium (Coniothyrium), further study is needed to confirm the status of these three strains..
523. K. SASAKI, H. NAKANO, W. WILOPO, T. HIRAJIMA, Performance of Arsenic Removal in Groundwater by a Permeable Reactive Barrier Using Zero Valence Iron., Proc. Intl. Symp. on Health Hazard by Arsenic Contamination of Groundwater and its Countermeasures, 148-151, 2006.11.
524. W. WILOPO, K. SASAKI, H. NAKANO, T. HIRAJIMA, Column Study for Immobilization of Arsenic and Manganese in Groundwater Using Iron Granular and Cow Manures., Proc. Intl. Symp. on Health Hazard by Arsenic Contamination of Groundwater and its Countermeasures, 143-147, 2006.11.
525. Jonathan P. Gramp, Keiko SASAKI, Jerry M. Bigham, Olia V. Karnachuk, Olli H. Tuovinen, Formation of covellite (CuS) under biological sulphate-reducing conditions., Geomicrobiology Journal, 23, 613-619, 2006.11.
526. Production of Bio-Coal Fuel from Low Rank Coal and Woody Biomass Mixture by Using a Bench-Scale Continuous Hydrothermal Equipment.
527. Keiko SASAKI, Minoru Matsuda, Tsuyoshi Hirajima, Keishi Takano, Hidetaka Konno, Immobilization of Mn(II) by a Mn-oxidizing fungus Paraconiothryum sp. like strain at neutral pHs., Mater. Trans., 47, 10, 2457-2461, 2006.10.
528. Keiko Sasaki, Minoru Matsuda, Tsuyoshi Hirajima, Keishi Takano, Hidetaka Konno, Immobilization of Mn(II) ions by a Mn-oxidizing fungus paraconiothyrium sp.-like strain at neutral pHs, Materials Transactions, 10.2320/matertrans.47.2457, 47, 10, 2457-2461, 2006.10, A Mn-oxidizing fungus was isolated from a constructed wetland of Hokkaido (Japan), which is receiving the Mn-impacted drainage, and genetically and morphologically identified as Paraconiothyrium sp.-like strain. The optimum pHs were 6.45-6.64, where is more acidic than those of previously reported Mn-oxidizing fungi. Too much nutrient inhibited fungal Mn-oxidation, and too little nutrient also delayed Mn oxidation even at optimum pH. In order to achieve the oxidation of high concentrations of Mn like mine drainage containing several hundreds g·m-3 of Mn, it is important to find the best mix ratio among the initial Mn concentrations, inoculumn size and nutrient concentration. The strain has still Mn-tolerance with more than 380 g·-3 of Mn, but high Mn(II) oxidation was limited by pH control and supplied nutrient amounts. The biogenic Mn deposit was poorly crystallized birnessite. The strain is an unique Mn-oxidizing fungus having a high Mn tolerance and weakly acidic tolerance, since there has been no record about the property of the strain. There is a potentiality to apply the strain to the environmental bioremediation..
529. Hidetaka KONNO, Yuuki OGAWA, Hideki TACHIBANA, Keiko SASAKI, Morphological Effect of Carbon Materials on the Activity of Mn(II)-oxidizing Fungus in Aqueous Media, Proc. Carbon 2006, 2006.07.
530. K. Sasaki, T. Sakimoto, M. Endo and H. Konno, FE-SEM study of microbiologically formed jarosites by Acidithiobacillus ferrooxidans., Mater. Trans., 47(4), 1155-1162, 2006.05.
531. Keiko Sasaki, Takashi Sakimoto, Mai Endo, Hidetaka Konno, FE-SEM study of microbially formed jarosites by Acidithiobacillus ferrooxidans, Materials Transactions, 10.2320/matertrans.47.1155, 47, 4, 1155-1162, 2006.04, Morphological characterization of jarosite groups formed from Fe(III) biologically oxidized with different numbers of Acidithiobacillus ferrooxidans was conducted using FE-SEM. The higher population of A. ferrooxidans resulted in more distinct jarosite mineral shape, and stronger Raman intensities for potassium jarosite, ammoniojarosite and argentojarosite. The morphology of the jarosites might be dependent on iron-oxidizing activity of A. ferrooxidans. The technique was applied to identify jarosite compounds formed during microbially mediated dissolution of arsenopyrite by A. ferrooxidans. It is difficult to identify this jarosite compound by X-ray diffraction and Raman spectroscopy because amounts are typically low and the crystallization is poor in minerals formed by microbially mediated oxidation. However, FE-SEM image provided helpful information for identification of jarosite compounds. The results suggest that morphology would provide useful information for identification and history of jarosite minerals as geochemical samples..
532. Keishi TAKANO, Yasoo ITOH, Tagiru OGINO, Kunihiko KUROSAWA, Keiko SASAKI, Phylogenetic analysis of manganese-oxidizing fungi isolated from manganese-rich aquatic environment in Hokkaido, Japan., Limnology, 2006.01.
533. , [URL].
534. T. Hirajima, A. Bissombolo, K. Sasaki, K. Nakayama, H. Hirai, and M. Tsunekawa, Floatability of rare earth phosphors from waste fluorescent lamps, Intl. J. Miner. Proc., 10.1016/j.minpro.2005.05.002, 77, 4, 187-198, 77, 187-198, 2005.11.
535. T. Hirajima, K. Sasaki, A. Bissombolo, M. Hamada, M. Tsunekawa, Feasibility of an efficient recovery of rare earth-activated phosphors from waste fluorescent lamps through dense-medium centrifugation., Separation and Purification Technology, 10.1016/j.seppur.2004.12.014, 44, 3, 197-204, 44, 197-204, 2005.07.
536. Nonaka Moriyasu, Tsuyoshi Hirajima, Keiko Sasaki, Fundamental investigation of hydrothermal treatment of lowrank coal and woody biomas mixture, The 2nd International workshop on Earth Science and Technology, 2004.12.
537. Nonaka Moriyasu, Tsuyoshi Hirajima, Keiko Sasaki, Hydrothermal treatment of low rank coal and woody biomass mixture, International Symposium on Green Technology for Resources and Materials Recycling, 2004.11.
538. Hidetaka Konno, Mai Endo, Hideki Tachibana, Keiko Sasaki, Removal of dissolved manganese ions by bio-remediation with carbon fiber, International Symposium on Materials for the 21th Century, 2004.10.
539. Keiko Sasaki, David Blowes, Carol Ptacek, Spectroscopic study of removal of Se(VI) from mine drainage by areactive permeable barrier column, Groundwater Quality, 2004.07.
540. K. Sasaki, H. Konno, M. Endo, K. Takano, Removal of Mn(II) ions by manganese-oxidizing fungus at neutral pHs in the presence of carbon fiber., Biotechnol. Bioengng., 85(5), 491-496, 2004.06.
541. Activation of manganese-oxidizing fungus with carbon fiber
- Fibrous shape is essential -.
542. Keiko Sasaki, Hidetaka Konno, Mai Endo, Keishi Takano, Removal of Mn(II) Ions from Aqueous Neutral Media by Manganese-Oxidizing Fungus in the Presence of Carbon, Biotechnology and Bioengineering, 10.1002/bit.10921, 85, 5, 489-496, 2004.03, A manganese-oxidizing fungus was isolated from a hot spring in Japan. The fungus was increasingly effective at oxidizing Mn(II) ions as the concentration of organic carbon sources in the growth medium was decreased. The fungus oxidized 50 ppm of Mn(II) ions within 160 h in a pH 7.3 medium at 25°C. The presence of carbon fiber shortened the time to 80 h, and promoted steady oxidation. The oxidation products were identified by XPS and XRD to be poorly crystallized and amorphous MnO2, both with and without the fiber. These results suggest that the fiber participates in kinetically limited oxidation. The fungus was entangled with and clung to the fibers, and the oxidized Mn species accumulated on the fungus. Similarly shaped polyethylene telephthalate fiber did not enhance the oxidation, nor was adhesion of the fungus observed. Although the mechanism is still unknown, the present work shows that removal of Mn from solution through the precipitation and accumulation of Mn-oxides on the fungus in the presence of carbon fiber is a promising improvement for water treatment..
543. K. K. Yoo, K. Sasaki, N. Hiroyoshi, M. Tsunekawa, T. Hirajima, The Effect of Mn2+ concentration on Mn removal by a sulfate-reducing bacteria bioreactor., Mater. Trans., 10.2320/matertrans.45.2429, 45, 7, 2429-2434, 2004.01.
544. K. K. Yoo, K. Sasaki, N. Hiroyoshi, M. Tsunekawa, Fundamental study on the removal of Mn2+ in acid mine drainage using sulfate-reducing bacteria., Mater. Trans., 10.2320/matertrans.45.2422, 45, 7, 2422-+, 2004.01.
545. Keiko Sasaki, Tagiru Ogino, Yuji Endo, Kunihiko Kurosawa, Field Study on Heavy Metal Accumulation in a Natural Wetland Receiving Acid Mine Drainage, Materials Transactions, 10.2320/matertrans.44.1877, 44, 9, 1877-1884, 2003.09, The mechanism of surface water remediation in a natural wetland that is receiving heavy metal-rich acidic mine drainage was investigated. Selective sequential extraction was useful to derive the mechanisms of heavy metal removal in the wetland. In the upstream portion of the wetland, dissolved Fe was removed mainly as oxide-bounded mineral phases, such as hydroxides. These are important for the subsequent removal of other heavy metals. Other ion-exchangeable and carbonate- bounded heavy metals are also observed in the upstream, associated with Fe oxides. Organic matter and Fe-Mn oxides in the upstream remove Cu and Zn ions from the drainage, respectively. In the middle of portion of the wetland the removal of heavy metal ions in relatively low concentrations occurs by the emergent vegetation. Greater clay abundance and higher microbial activity of sulfate reducing bacteria in the downstream parts achieved low-level removal of metals. Multi-cell wetlands are recommended for the treatment of acidic metal bearing surface water drainage, if sufficient land area and expenses are available to construct..
546. Keiko Sasaki, Tagiru Ogino, Osamu Hori, Yuji Endo, Kunihiko Kurosawa, Masami Tsunekawa, Chemical transportation of heavy metals in the constructed wetland impacted by acid drainage, Materials Transactions, 10.2320/matertrans.44.305, 44, 2, 305-312, 2003.02, Chemical transportation of heavy metals in the constructed wetland impacted by acid drainage was investigated seasonally using a combination of the selective sequential extraction of the sediments with elemental analysis of the emergent vegetation in the wetland. Manganese was dissolved from sediments in the constructed wetland by the contact with acid drainage, and then precipitated again as ion-exchangeable forms. It was expected that a part of Mn and Fe bound to oxides were flown out of the wetland as suspended particulate matters. It was observed that there is passive absorption of Mn in leaves of Phragmites austlaris in the upstream of the wetland. The transportation of Cu clearly showed the seasonal variation: there was the decomposition of organic substances with high molecular weights by soil microorganisms in summer. Therefore, Cu was complexed to the humic substances, and dramatically adsorbed onto the roots of Phragmites austlaris in down stream of the wetland. It was also observed that there is active absorption of Fe in roots and leaves of Phragmites austlaris. Most of the zinc was strongly bounded to the sediments, therefore, scarcely uptaken to the vegetation. It was also found that there were heavy metal distributions between plant organs..
547. K. Sasaki, M. Endo, K. Takano, H. Konno, Removal of manganese ions from water by fungi with carbon fiber.", Proc. Intl. Symp. BIOMINE'2003, 2003.01.
548. K. K. Yoo, K. Sasaki, N. Hiroyoshi, and M. Tsunekawa, Biological synthesis of metastable g-MnS by sulfate reducing bacteria., Proc. the Japan/Korea Intl. Symp. Resources Recycling and Material Sciences, 131-136, 2003.01.
549. K. Sasaki, O. Hori, T. Ogino, M. Tsunakawa, Accumulation of heavy metals in the emergent vegetations in the constructed wetland., Proc. the 16th Intl. Symp. Environ. Biogeochem., 2003.01.
550. K. Sasaki, H. Kobayashi, K. Yoo and M. Tsunekawa, Morphologies of aragonite synthesized from scallop shells and lime stones by successive reaction., Proc. 6th Intl. Symp. East Asian Recycl. Technol., 331-336, 2001.01.
551. K. Sasaki, M. Endo, K. Kurosawa, and H. Konno, Bioaccumulation of manganese for water treatment with carbon fiber., Proc. Intl. Symp. BIOMINE'2001, 279-286, 2001.01.
552. K. Sasaki, T. Yamashita, M. Tsunekawa, Synthesis of aragonite from calcined scallop shells - Morpholigical characterization by FE-SEM., Shigen-to-Sozai, 118, 553-558, 2002.01.
553. K. Sasaki, M. Endo, K. Kurosawa, and H. Konno, Removal of manganese ions from water by Leptothrix discophora with carbon fiber., Mater. Trans., 43(11), 2773-2777, 2002.01.
554. K. Sasaki, N. Haga, T. Hirajima, K. Kurosawa, M. Tsunekawa, Distribution and transition of heavy metals in mine tailing dumps., Mater. Trans., 43(11), 2778-2783, 2002.01.
555. K. K. Yoo, K. Sasaki, T. Hirajima, M. Tsunekawa, Analysis of heavy metals in a tailing impoundment of abandoned Mn mine by using two sequential extractions., Mater. Trans., 43(12), 3189-3194, 2002.01.
556. K. Sasaki, T. Ogino, Y. Endo, K. Kurosawa, Field study on heavy metal accumulation in the natural wetland receiving acid mine drainage, Mater. Trans., 44(9), 1877-1884, 2003.01.
557. K. Sasaki, T. Ogino, O. Hori, Y. Endo, K. Kurosawa, M. Tsunekawa, Chemical transportation of heavy metals in the constructed wetland impacted by acid drainage., Mater. Trans., 44(2), 305-312, 2003.01.
558. Kyoungkeun Yoo, Keiko Sasaki, Tsuyoshi Hirajima, Masami Tsunekawa, Analysis of heavy metals in a tailing impoundment of abandoned Mn mine by using two sequential extractions, Materials Transactions, 10.2320/matertrans.43.3189, 43, 12, 3189-3194, 2002.12, The tailing impoundment was investigated for vertical distribution of minerals by X-ray fluorescence analysis (XRF), powder X-ray diffraction (XRD), and two sequential extraction methods. It was found that Si, Mn, and Fe occupied over 80% in mass balance of XRF, and present as constituents of clay minerals, oxides, and pyrite, respectively. Therefore, the sampling site was regarded as chemically stable. Two sequential extraction methods were complementary to each other, therefore, the combination of two methods is useful for further analysis of sediments including variable minerals..
559. Keiko Sasaki, Takanori Haga, Tsuyoshi Hirajima, Kunihiko Kurosawa, Masami Tsunekawa, Distribution and transition of heavy metals in mine tailing dumps, Materials Transactions, 10.2320/matertrans.43.2778, 43, 11, 2778-2783, 2002.11, The vertical distributions of heavy metals and other elements in sediment core samples in a landfill of abandoned mine tailings were examined. Core samples were analyzed by XRF and XRD, and further examined by ICP-AES measurements after acid-sequential extraction with HCl, HF, and HNO3. According to XRD, the sediments contained α-quartz as the main component, and sericite, chlorite, rhodochrosite, pyrite, jarosite, sphalerite, and galena as minor components. A complete decomposition method using sequential extraction for the mine tailings sediments was established at ambient temperatures. Acid sequential extraction was useful for the analysis of minerals in mine tailings which are difficult to detect by XRD. Rhodochrosite and chlorite were dissolved by HCl-extraction, quartz and sericite by HF-extraction, and sulfides by HNO3-extraction. Rhodochrosite was the main source of high concentrations of Mn in mine drainage, highly distributed below the - 100 cm zone in the mine tailings, combined with pyrite but not with sericite and quartz. The distributions of most heavy metals were related to those of pyrite..
560. Keiko Sasaki, Mai Endo, Kunihiko Kurosawa, Hidetaka Konno, Removal of manganese(II) ions from water by Leptothrix discophora with carbon fiber, Materials Transactions, 10.2320/matertrans.43.2773, 43, 11, 2773-2777, 2002.11, To apply manganese-oxidizing bacteria to waste water treatment, basic performance of the manganese-oxidizing bacterium, Leptothrix discophora, distributed by ATCC was examined. In addition, the effect of carbon fiber on the oxidation by the bacterium was also investigated, since carbon fiber was reported to accelerate the growth of activated sludge during sewage treatment. The bacterium was found to be active in the medium containing 24 ppm Mn(II) ions, the concentration being about 8 times higher than the recommended one and practically useful level. The oxidation rate was higher with the static culture than the shaking culture. This was considered to be due to physical damage to the sheath structure of bacteria which is reported to be important to oxidize Mn(II) ions. The carbon fiber did not accelerate the microbial oxidation of Mn(II) ions. This is partly attributed to the lack of contact between the bacterial cell, which floated as thin membranes, and the carbon fiber sunk in the bottom of vessels. However, oxidized Mn species precipitated on the carbon fiber, which resulted in an improvement of the transparency of water. This effect is different from the one caused by activated carbons, since the carbon fiber has very low specific surface area and no pore structure. The effect was more remarkable in the shaking culture than the static culture, indicating that organic substances originated from the bacterium play an important role in the adsorption of oxidized Mn species..
561. Keiko Sasaki, Hidetaka Konno, Morphology of jarosite-group compounds precipitated from biologically and chemically oxidized Fe ions, Canadian Mineralogist, 10.2113/gscanmin.38.1.45, 38, 1, 45-56, 2000.02, Jarosite-group compounds [MFe3(SO4)2(OH)6: argentojarosite (M+ = Ag+), jarosite (M+ = K+), ammoniojarosite (M+ = NH4+)] were synthesized by supplying Fe3+ ions in three different ways: biological oxidation of Fe2+ ions by T. ferrooxidans (biological products), chemical oxidation of Fe2+ ions by slow addition of H2O2 (chemical products 1), and chemical oxidation by rapid addition of H2O2 (chemical products 2). These were characterized by XRD, FTIR, chemical analysis and SEM; as well, the morphological features were compared with those formed by the hydrothermal method (standard substances). The jarosite-group compounds so synthesized do not contain crystalline by-products, as revealed by XRD, but the order of purity inferred from IR spectra, which is determined by the intensity of specific peaks, was found to be dependent on the method of preparation and is independent of the jarosite species; the order was found to be standard substances > chemical products 2 > chemical products 1 > biological products. Two main factors were found to affect the morphology, the method and rate of supply of Fe3+ ions to the system and the nature of the monovalent cations, which determine the intrinsic rate of formation under given conditions. Where Fe3+ ions are present in the system from the beginning, the order of rate of formation is confirmed to be argentojarosite > jarosite > ammoniojarosite at 30°C. Morphological features of jarosite-group phases formed by the biological method were rendered distinguishable by the effect of extracellular substances. Morphological information is useful to distinguish the mode of occurrence of jarosite-group phases in natural samples, since it may be difficult to do so by other analytical techniques, such as XRD, FTIR, Raman spectroscopy and chemical analysis..
562. K. Sasaki, H. Konno, Morphological change of jarosite groups formed from biologically and chemically oxidized Fe(III) ions., Can. Mineral., 38, 45-56, 2000.01.
563. Ken Nakayasu, Masami Fukushima, Keiko Sasaki, Shunitz Tanaka, Hiroshi Nakamura, Comparative studies of the reduction behavior of chromium(VI) by humic substances and their precursors, Environmental Toxicology and Chemistry, 10.1897/1551-5028(1999)018<1085:CSOTRB>2.3.CO;2, 18, 6, 1085-1090, 1999.05, Hexavalent chromium (Cr[VI]) is reduced by dissolved organic carbons (DOCs) such as humic substances, tannic acid (TA), and gallic acid (GA). The kinetic constants and the resulting chemical species after the reduction were compared with each other. The kinetic constants for GA and TA, which are model precursors of humic substances, were two to three orders of magnitude larger than those for the humic substances when these kinetic constants were expressed as a function of the molar concentration of the reductive functional group (F(red)) in various DOCs. After the reduction of Cr(VI), the percentages of the species complexed with GA and TA were higher than those with the humic substances. This appears to be due to the formation of high molecular weight compounds by polymerization during the reduction of Cr(VI) and complexation of Cr(III) with the polymerized compounds. The UV-vis spectrophotometric data and gel permeation chromatography support this view..
564. Masami Fukushima, Shunitz Tanaka, Ken Nakayasu, Keiko Sasaki, Kenji Tatsumi, Evaluation of copper(II) binding abilities of humic substances by a continuous site-distribution model considering proton competition, analytical sciences, 10.2116/analsci.15.185, 15, 2, 185-188, 1999.02.
565. K. Sasaki, T. Hirajima and M. Tsunekawa, Morphological control of aragonite formed from waste scallop shells., Proc. 5th Intl. Symp. East Asian Recycling Technology., 147-150, 1999.01.
566. K. Sasaki, M. Tsunekawa, S. Tanaka, M. Fukushima and H. Konno, Inhibiting effect of natural organic acids on microbially mediated dissolution of pyrite in acidic environments., Shigen-to-Sozai, 115, 233-239, 1999.01.
567. K. Nakayasu, M. Fukushima, K. Sasaki, S. Tanaka, and H. Nakamura, Comparative studies of the reduction behavior of chromium (VI) by humic substances and their precursors., Environ. Toxicol. Chem., 18, 1085-1090, 1999.01.
568. M. Fukushima, S. Tanaka, K. Nakayasu, K. Sasaki, and K. Tatsumi, Evaluation of copper(II) binding abilities of humic substances by a continuous site-distribution model considering proton competition., Anal. Sci., 15, 185-188, 1999.01.
569. Keiko Sasaki, Osamu Tanaike, Hidetaka Konno, Distinction of jarosite-group compounds by Raman spectroscopy, Canadian Mineralogist, 36, 5, 1225-1235, 1998.10, Raman spectra (200-1300 cm-1) were measured for synthesized jarosite-group compounds [MFe3(SO4)2(OH)6, M+ = K+, NH4+, Na+, Ag+, and 1/2Pb2+). The Raman spectra of jarosite-group compounds are characterized by a tendency for the wavenumbers assigned to two vibrational modes of SO42-, ν1(SO42-) and ν3(SO42-), and three vibrational modes of Fe-O bonds, to decrease with increase in the c unit-cell parameter. The wavenumbers assigned to the ν2(SO42-) and ν4(SO42-) vibrational modes are independent of the value of c. For plumbojarosite, the peaks corresponding to the ν1(SO42-) and ν3(SO42-) vibrational modes are broad owing to two overlapping peaks assigned to two types of sulfate groups, SO42- ions adjacent and not adjacent to Pb2+ ions. Raman spectra can serve to identify the specific type of jarosite-group compound in poorly crystalline or low-concentration geochemical samples..
570. K. Sasaki, M. Tsunekawa, T. Ohtsuka, H. Konno, The role of sulfur-oxidizing bacteria Thiobacillus thiooxidans in pyrite weathering, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/S0927-7757(97)00200-8, 133, 3, 269-278, 1998.02, The role of the sulfur-oxidizing bacteria Thiobacillus thiooxidans in pyrite weathering was investigated to clarify the effects of the bacteria on the dissolution behavior of pyrite and the formation of secondary minerals using Raman spectroscopy and powder X-ray diffraction (XRD) in addition to solution analysis. It was found that T thiooxidans, when present with the iron-oxidizing bacteria Thiobacillus ferrooxidans, enhanced the dissolution of Fe and S species from pyrite, whereas T. thiooxidans alone did not oxidize pyrite. Enhancement of the consumption of elemental sulfur and regeneration of Fe(II) ions were also observed with T. thiooxidans together with T. ferrrooxidans, while this did not occur with T. ferrooxidans alone. It may be assumed that the contribution of T. thiooxidans to the formation of acid mine drainage on a geochemical scale should not be overlooked, though pyrite weathering is predominantly caused by iron-oxidizing activity in T. ferrooxidans..
571. K. Sasaki, M. Tsunekawa, T. Ohtsuka and H. Konno, The role of sulfur-oxidizing bacteria, Thiobacillus thiooxidans, in pyrite weathering., Colloids and Surfaces A: Phisicochemical and Engineering Aspects, 133(3), 269-278, 1998.01.
572. K. Sasaki, O. Tanaike and H. Konno, Distinction of jarosite compounds by Raman spectroscopy., Can. Mineral., 36, 1225-1235, 1998.01.
573. Keiko Sasaki, A Study on the Dissolution of Pyrite and Its Suppression in Acidic Environments, bunseki kagaku, 46, 7, 1997.12, To clarify the formation mechanism of acid mine drainage and to propose a method to alleviate this environmental problem, the microbially-mediated dissolution of pyrite and its suppression was investigated. First, the dissolution of pyrite with the iron-oxidizing bacteria, Thiobacillus ferrooxidans, was investigated by both a solution analysis (ICP-AES) and a mineral-surface analysis (XRD, XPS, FTIR, and XMA). A microbial attack on pyrite by T. ferrooxidans proceeds mainly by the "indirect contact mechanism". An abiotic dissolution of pyrite with Fe(III) ions around pH 2 was found to be suppressed by the complexation of Fe(III) ions with anionic ligands, such as oxalate, and also by a preferential adsorption of Cu(II) and Fe(II) ions. Tannic and fulvic acids were found to be more effective inhibitors of T. ferrooxidans and T. thiooxidans than oxalic acid, reported by others. Finally, originally isolated fulvic acids were used to elucidate the suppression of the microbially mediated dissolution of pyrite by T. ferrooxidans and T. thiooxidans. The suppression was due to the inhibition of microorganisms by organic acids and their adsorption to active sites of the pyrite surface, as well as the reduction and complexation of Fe(III) ions by them. The results indicate that humic substances would be useful for the remediation and prevention of damage caused by acid mine drainage..
574. Keiko Sasaki, Raman study of the microbially mediated dissolution of pyrite by Thiobacillus ferrooxidans, Canadian Mineralogist, 35, 4, 999-1008, 1997.08, Raman spectroscopy was applied to the microbially mediated dissolution of pyrite by high density (more than 109 cells) of Thiobacillus ferrooxidans. In the range 600-200 cm-1, peaks corresponding to secondary minerals such as elemental sulfur and jarosite were observed in addition to those of pyrite. Small amounts of elemental sulfur and poorly crystalline jarosite were detected by Raman spectroscopy, but are undetectable by X-ray diffraction and Fourier transform infrared spectroscopy. Ammoniojarosite was predominantly formed in microbially mediated dissolution of pyrite with a high density of cells, whereas jarosite was formed in the sterilized control. This finding is probably ultimately due to the much greater amount of jarosite precursors (Fe3+ sulfate complexes) formed by the bacterial oxidation of iron. Initially, and in both cases, the kinetically favored jarosite appeared, but in the presence of bacteria, there was so much precursor present that the available potassium was exhausted. Ammoniojarosite subsequently was formed. In the sterilized control, precursors were less readily formed, and jarosite formed. There was no evidence for direct involvement of bacteria in the formation of jarosite. The changes in mineral compositions are correlated with those in the solutions. Raman spectroscopy was used to follow compositional changes in minerals during the microbially mediated dissolution of pyrite..
575. K. Sasaki, M. Tsunekawa, S. Tanaka and H. Konno, Suppression of pyrite weathering by humic substances., Proc. Intl. Symp. BIOMINE, 1997.01.
576. K. Sasaki, Raman study of the microbially mediated dissolution of pyrite by Thiobacillus ferrooxidans., Can. Mineral., 35(4), 999-1008, 1997.01.
577. M. Fukushima, S. Tanaka, K. Nakayasu, K. Sasaki, H. Nakamura and K. Tatsumi, Investigation of copper(II)-binding behavior of fulvic acids by three-dimensional fluorescence spectrometry., Anal. Sci., 13, 1007-1011, 1997.01.
578. Masami Fukushima, Shunitz Tanaka, Ken Nakayasu, Keiko Sasaki, Hiroshi Nakamura, Kenji Tatsumi, Investigation of Copper(II)-Binding Behavior of Fulvic Acids by Three-Dimensional Fluorescence Spectrometry, analytical sciences, 10.2116/analsci.13.1011, 13, 6, 1011-1015, 1997.01.
579. K. Sasaki, M. Tsunekawa, S. Tanaka, H. Konno, Suppression of microbially mediated dissolution of pyrite by originally isolated fulvic acids and related compounds, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/S0927-7757(96)03765-X, 119, 2-3, 241-253, 1996.12, Originally isolated fulvic acids (FA) were applied to the suppression of microbially mediated dissolution of pyrite by Thiobacillus ferrooxidans and Thiobacillus thiooxidans, and compared with tannic acids (TA) and oxalic acid (OA). The mechanism of suppression was studied using X-ray photoelectron spectrometry, Fourier transformed infrared spectroscopy, and solution analysis. Preliminary experiments showed that the reaction rate of Fe(III) with pyrite was faster than the rate of reduction of Fe(III) to Fe(II) by FA, and that FA adsorbed to the pyrite surface and moderately suppressed dissolution of the pyrite. Release of S and Fe species and decreases in pH in the microbially mediated dissolution of pyrite were effectively suppressed in the presence of more than 10 ppm of TA, 200 ppm of FA, and 250 ppm of OA. The suppression was considered to be due to the inhibition of microorganisms by organic acids and their adsorption to the active sites of pyrite surfaces in addition to reduction and complexation of Fe(III) ions by these acids. The results indicate that humic substances are useful for remediation in mine environments..
580. K. Sasaki and M. Tsunekawa, Evaluation of tannic and fulvic acids as inhibitors of cell growth, and iron and sulfur oxidation in Thiobacillus ferrooxidans and Thiobacillus thiooxidans., Shigen-to-Sozai (J. Min. Mat. Proc. Inst. Japan), 112, 929-933, 1996.01.
581. K. Sasaki, M. Tsunekawa and H. Konno, Effect of cations on pyrite oxidation with Fe(III) ions near pH 2., Shigen-to-Sozai (J. Min. Mat. Proc. Inst. Japan), 112, 231-237, 1996.01.
582. K. Sasaki, M. Tsunekawa and H. Konno, Effect of Fe(II) ions on pyrite oxidation with Fe(III) ions near pH 2., Shigen-to-Sozai (J. Min. Mat. Proc. Inst. Japan), 112, 49-53, 1996.01.
583. K. Sasaki, M. Tsunekawa, S. Tanaka and H. Konno, Suppression of microbially mediated dissolution of pyrite by originally isolated fulvic acids and related compounds., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 119, 241-253, 1996.01.
584. Keiko Sasaki, M. Tsunekawa, K. Hasebe, H. Konno, Effect of anionic ligands on the reactivity of pyrite with Fe(III) ions in acid solutions, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/0927-7757(95)03142-Z, 101, 1, 39-49, 1995.08, The reactivity of pyrite with Fe(III) ions in solutions of pH around 2 containing anionic species was evaluated by the determination of released Fe(II) ions, and by surface analysis of pyrite using X-ray photoelectron spectroscopy (XPS). The release of Fe(II) ions decreased with increasing concentration of total anionic species, and the suppression of pyrite dissolution was in the order chloride6]3- complexes did not function as oxidants. For [Fe(CN)6]3-, the results were explained by a mechanism based on molecular orbital theory, since the complex is inert and of low-spin type. For the others, the order of suppression was found to be in parallel with the order of potential as oxidant, the standard redox potential,E0. The redox couples of Fe(III)-CDTA and Fe(III)-oxalate complexes have lowerE0 values and this is considered to be the reason for no oxidation. In the phosphate system, colloid formation and polynucleation of Fe(III) ions were observed and these were additional factors in the suppression. The experimental results and the calculatedE0 values indicate thatE0 for SO42- /pyrite-S may be around 0.3 V. This means thatE0 is an important measure for estimating the ligand effect..
585. K. Sasaki, M. Tsunekawa, T. Ohtsuka and H. Konno, Confirmation of sulfur-rich layer formed on pyrite after dissolution by Fe(III) ions around pH 2., Geochim. Cosmochim. Acta, 59, 3155-3158, 1995.01.
586. K. Sasaki, M. Tsunekawa, K. Hasebe and H. Konno, Effect of anionic ligands on the reactivity of pyrite with Fe(III) ions in acid solutions., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 101, 39-49, 1995.01.
587. K. Sasaki, M. Tsunekawa and H. Konno, Characterization of argentojarosite formed from biologically oxidized Fe(III) ions., Can. Mineral., 33(6), 1311-1319, 1995.01.
588. Keiko Sasaki, Masami Tsunekawa, Toshiaki Ohtsuka, Hidetaka Konno, Confirmation of a sulfur-rich layer on pyrite after oxidative dissolution by Fe(lIl) ions around pH2, Geochimica et Cosmochimica Acta, 10.1016/0016-7037(95)00203-C, 59, 15, 3155-3158, 1995.01, The stoichiometry of pyrite dissolution by Fe(II) ions was studied in chloride media around pH 2. Pyrite was found to dissolve nonstoichiometrically during the initial tens of hours and a S-rich layer was formed on the pyrite due to preferential dissolution of iron. The major constituent of the layer was elemental S, identified by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy..
589. K. Sasaki, M. Tsunekawa, H. Konno and K. Hasebe, Effect of anionic species on the oxidative dissolution of pyrite in acid solutions., Proc. Intl. Symp. Trace Analysis '94, 291-294, 1994.01.
590. K. Sasaki, H. Konno and M. Inagaki, Structural strain in pyrite evaluated by X-ray powder diffraction., J. Mater. Sci., 29, 1666-1669, 1994.01.
591. K. Sasaki, Effect of grinding on the rate of oxidation of pyrite by oxygen., Geochim. Cosmochim. Acta, 58, 4649-4655, 1994.01.
592. Keiko Sasaki, Effect of grinding on the rate of oxidation of pyrite by oxygen in acid solutions, Geochimica et Cosmochimica Acta, 10.1016/0016-7037(94)90197-X, 58, 21, 4649-4655, 1994.01, Solubility of pyrite (FeS2) ground for different periods was investigated in acid solutions in air. In the initial dissolution, up to 50 h, the dissolution rate, r, was high, due to oxidized species such as FeSO4 formed by grinding. After 50 h, the surface of pyrite was exposed and the dissolution rate decreased. The formation and dissolution of oxidized species were confirmed by X-ray photoelectron spectroscopy, XPS. From the dissolution rates of Fe and S species, rFe and rS, for 50-200 h, it was found that pyrite dissolves nonstoichiometrically ( rS rFe < 2) and that grinding promotes the dissolution of sulfur species leading to the stoichiometric dissolution ( rS rFe = 2). The increase in rS can be explained by the displacement of S atoms in the crystal due to the grinding. The effective Debye-Waller parameter, Beff, depends on the displacement of constituent atoms in the crystal from their equilibrium positions and is measured from the diffraction intensities of X-rays. The parameter for S atoms in pyrite, Beff(S), increased by one or two orders of magnitude with increasing grinding time, tG, while that for the pyrite, Beff(FeS2), did not change markedly. It was established that rS is closely related to Beff(S). The phenomenon may be regarded as a type of mechanical activation..
593. Keiko Sasaki, Masami Tsunekawa, Hidetaka Konno, Nonstoichiometry in the oxidative dissolution of pyrite in acid solutions., bunseki kagaku, 10.2116/bunsekikagaku.43.911, 43, 11, 911-917, 1994.01, The oxidative dissolution of pyrite, FeS2, by Fe(III) ions in hydrochloric acid solutions at around pH 2 was investigated by spectrophotometry, ICP-AES and X-ray photoelec-tron spectroscopy (XPS). All the experimental results showed that the preferential dissolution of iron in pyrite took place resulting in the formation of a surface layer enriched with sulfur. The preferential dissolution was enhanced by increasing the initial concentration of Fe(III) ions. Accordingly, a classical stoichiometric dissolution ([Fe]/[S] = 0.5) mechanism can not explain the present results. The dissolution rate was independent of CI ion concentration, but dependent on Fe(II) ion concentration. The oxidative dissolution of pyrite was suppressed by increasing the concentration of Fe(II) ions. The present results suggest that the kinetic equations should be formulated, considering both dissolved iron and sulfur species..
594. Keiko Sasaki, H. Konno, M. Inagaki, Structural strain in pyrites evaluated by X-ray powder diffraction, Journal of Materials Science, 10.1007/BF00368943, 29, 6, 1666-1669, 1994.01, Two parameters for measuring the structural strain, the effective Debye-Waller parameter, Beff, and lattice strain, e{open}, were evaluated on a natural pyrite (FeS2) after grinding. The effective Debye-Waller parameter, Beff, which depends on the displacement of atoms in the crystal, was calculated for the overall crystal, Beff(FeS2), and for sulphur, Beff(S), from the intensities of the X-ray diffraction lines. The Beff(S) increased markedly with increasing grinding time, while Beff(FeS2) did not change significantly. The lattice strain, e{open}, was not recognized. These observations suggest that the displacement of sulphur atoms preferentially takes place by grinding. The relations between these Beff values and crystallite size, L, were observed to be common for two different methods of grinding. This tendency was considered to be an inherent property of pyrite. The value of Beff(S) is a useful index to estimate mechanically caused strain in pyrite..
595. Hidetaka Konno, Keiko Sasaki, Masami Tsunekawa, Takakatsu Takamori, Ryusaburo Furuichi, X-Ray photoelectron spectroscopic analysis of surface products on pyrite formed by bacterial leaching, bunseki kagaku, 10.2116/bunsekikagaku.40.11_609, 40, 11, 609-616, 1991.01, Bacterial leaching is often applied to recover useful metallic elements from low grade ores; an understanding of the leaching mechanism is necessary to improve the efficiency of this process. In the present work, surface analysis by XPS was carried out on pyrite (FeS2) after leaching with Thiobacillus ferrooxidans for 1 to 11 d. The measured complex spectra were analyzed by the concept of differential charging effects; it was found that Fe(II, III), S, SO42-, and probably SO32-, are formed on the pyrite. The accumulation of K ions was also found with more than 6 d of leaching. Although the observed elemental S is considered to be an intermediate product in the indirect leaching mechanism, the formation on pyrite particles during the bacterial leaching has not been directly observed. The assignment of the SO32- peak is still conditional but, as a metabolic intermediate, the formation of SO32- ions in the cell has been proposed by others. The time variations in the mole ratios of species of S or K vs. Fe in the surface products are helpful to understand the leaching mechanism. The accumulation of Fe(III), SO42-, K+ and OH- ions on the surface with leaching suggests the formation of insoluble compounds, such as jarosite (chemical formula: K[Fe3(SO4)2(OH)6])..
596. Takakatsu Takamori, Keiko Sasaki, Masami Tsunekawa, Tsuyoshi Hirajima, Leaching behavior and its mechanism in the leaching of a chalcopyrite concentrate by Thiobacillus ferrooxidans, Shigen to sozai, 106, 4, 15-22, 1990.04, Leaching behavior of a chalcopyrite concentrate by Thiobacillus ferrooxidans strain isolated from an acid mine water was considered on the basis of the results of batch shake flask experiments. Under the same pulp density, there is a linear relation between the initial specific surface area and the upper limit of copper concentration attainable with a high leaching rate. Leaching proceeded in two stages. The first stage was characterized by a high growth rate, high demand of hydrogen ion and a high leaching rate. The second stage was characterized to generation of hydrogen ion, a low leaching rate, and a low growth rate. The leaching mechanism of the first stage is mainly indirect, and the reactions proceed by depositing elemental sulphur on the mineral surface until reaching a particular thickness. In the second stage, the deposited elemental sulfur is dissolved by bacterial catalytic action and sulfuric acid is produced. The main factor affecting the rate in the leaching is oxidation of sulfide to sulfate. For improvement in leaching rate, it is necessary to accelerate this reaction..
597. Takakatsu Takamori, Takuya Yamamoto, Keiko Sasaki, Masami Tsunekawa, Tsuyoshi Hirajima, Leaching behavior of a chalcopyrite concentrate in the coexistent system of thiobacillus thiooxidans with thiobaccilus ferroxidans, and phospholipid as extracellular substances, Shigen to sozai, 10.2473/shigentosozai.106.611, 106, 10, 611-616, 1990.01, In the previous report, the authors considered the leaching mechanism of chalcopyrite concentrate by Thiobacillus ferrooxidans, and pointed out that leaching rate was mainly controlled by the deposition of elemental sulphur on the mineral surface. In this report, the effect of the coexistence of Thiobacillus thiooxidans, whose energy source is elemental sulphur, with Thiobacillus ferrooxidans on the leaching of a chalcopyrite concentrate was investigated. During the culture of both species the relation between the surface tension of the culture medium and cell number was examined, and the phospholipid which is one of the extracellular substances in the culture of both microorganisms were qualitatively analyzed by thin layer chromatography. The leaching efficiency of a chalcopyrite was conspicuously improved by the coexistence of Thiobacillus thiooxidans with Thiobacillus ferrooxidans. The results indicated that in order to make efficient the leaching of chalcopyrite concentrate, it is necessary that the reactions of equations (1) to (3) or (4) mentioned in the text must consecutively proceed. However, the initially high leaching rate of chalcopyrite did not continue to the complete dissolution of chalcopyrite. The reason is that the growth of Thiobacillus thiooxidans was depressed by the increase of ferrous ion concentration, and that it became impossible to keep the sequence in the above mentioned reactions. Accordingly it is indicated that in order to improve further the efficiency of leaching it is necessary to artificially control the chemical constituents of the leaching solution. As the cell number increased, the surface tension of the culture medium decreased. Phosphatidylethanolamine and phosphatidylglycerol were detected as phospholipid. The phospholipid is polar-nonpolar substance, accordingly these extracellular substances would affect the leaching rate..
598. M. Sugawara, K. Sasaki, T. Kambara, Surface-tention titration of calcium(II)and Manganese (II) by using triethanolamine as masking reagent, Fresenius Z. Anal. Chem., 313,237, 1982.12.