記述言語：英語   掲載種別：研究論文（学術雑誌）  

Ferrihydrite is omnipresent in nature, and its adsorption of As(III/V) decides the migration of arsenic. Although As(III) is commonly recognized as the more mobile species of inorganic arsenic, it sometimes exhibits less mobility in ferrihydrite systems, which calls for further insights. In this study, we elucidated the adsorption behavior and mechanisms of As(III/V) on ferrihydrite under different loading levels (molar ratio As/Fe = 0-0.38), solution pH (3-10), and coexisting ions [P(V) and Ca(II)] based on batch adsorption experiments, surface complexation modeling, density functional theory calculations, and X-ray photoelectron spectroscopy. Our results show that As(III) exhibits weaker adsorption affinity but a larger capacity compared with that of As(V). On ferrihydrite, As(III) and As(V) are adsorbed mainly as bidentate mononuclear complexes at type-a sites [≡Fe(OH-0.5)2] and bidentate binuclear complexes at type-b sites (2≡FeOH-0.5), respectively. As the dosage increases, As(III) further forms mononuclear monodentate complexes at both surface sites, resulting in a higher site utilization efficiency, while As(V) does not due to repulsive electrostatic interaction. The difference in surface species of As(III/V) also leads to complex responses when coexisting with high concentrations of P(V) and Ca(II). This study helps us to understand environmental behavior of As(III/V) and develop remediation strategy in As(III/V) contaminated systems.

DOI： 10.1021/acs.est.4c05795

PubMed

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Informa UK Limited  

DOI： 10.1080/00219592.2024.2366409

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掲載種別：研究論文（学術雑誌）  

Ferrous sulfate (FeSO4) combined with acid pretreatment is usually employed to remediate contaminated soils containing Cr(VI). However, the long-term efficiency of this stabilization method is important for its sustainability. In this study, a gradient temperature-elevating exposure test was employed to investigate the stability of Cr in FeSO4-remediated soil when exposed to elevated temperatures (40 °C, 120 °C, and 500 °C), possibly caused by hot weather and/or wildfires. The results of chemical extraction and X-ray absorption near edge structure spectroscopy (XANES) showed that the Cr(VI) in contaminated soil was successfully transformed to Cr(III) after stabilization, resulting in the dramatic decrease of water-leachable Cr(VI). The stabilization efficiency was further improved under 40 °C treatment after 30 days. Subsequently, the 120 °C treatment (7 days) had relatively little effect on the Cr speciation and mobility in soils. However, even one day of 500 °C calcination resulted in the deterioration of stabilization efficiency, and the water-leachable Cr(VI) re-increased and became higher than the Chinese environmental standards (total Cr 15 mg/L, Cr(VI) 5 mg/L) for the classification of hazardous solid wastes. XANES results reflected that heating at 500 °C facilitate the formation of Cr2O3, which was mainly caused by thermal decomposition and dehydration of Cr(OH)3 in the soil. Besides, the transformation of Cr species resulted in the enhanced association of Cr with the most stable residual fraction (88.3%–91.6%) in soil. Based on chemical extraction results, it was suggested that the oxidation of Cr(III) to Cr(VI) contributed to the re-increased mobility of Cr(VI) in soil. However, the XANES results showed that almost no significant re-oxidization of Cr(III) to Cr(VI) happened after heating at 500 °C, which was probably caused by XANES linear combination fits (LCF) uncertainties. Moreover, the changes in soil properties, including a rise in pH to a slightly alkaline range and/or the decomposition of organic matter, possibly contributed to the enhanced mobility of Cr(VI) in soil. This study contributes to clarifying the mobility and transformation of Cr in contaminated soils and provides a support for the sustainable management of remediated soils.

DOI： 10.1016/j.jenvman.2024.120457

Scopus

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掲載種別：研究論文（学術雑誌）  

Conventional neutralization treatment for manganese (Mn)-bearing mine drainage provides a challenge of cost-efficiency, and new approaches should be explored for efficient removal of Mn. We focused on Mn neutralization sludge, a by-product of the Mn-bearing drainage treatment process, which was assumed to be useful as a water purification material. Mn and zinc (Zn) removal tests in simulated drainage were performed using Mn neutralization sludge, and the reaction mechanism was elucidated using geochemical modeling and X-ray absorption fine structure (XAFS) analysis. The results showed that the addition of sludge enabled to lower the Mn and Zn concentration below Japanese effluent standard (10 mg dm−3 for Mn; 2 mg dm−3 for Zn) within 1 h. Furthermore, heavy metal immobilization was achieved at neutral pH (7–8) with the sludge addition, while the conventional neutralization process without adding the sludge requires higher pH (>10) to lower Mn concentration. These removal behaviors were not explainable by considering only well-known phenomena: hydroxide precipitation, surface complexation reaction onto δ-MnO2, and autocatalytic Mn oxidation. Hence, we advanced the geochemical model for simulation, suggesting that a surface complexation reaction onto γ-MnOOH greatly contributed to the removal of Mn. Besides, Zn was calculated to be predominantly precipitated as ZnMn2O4. Solid residue analysis by XAFS measurement supported the result of above calculation, validating the reliability of the constructed geochemical model. Overall, we concluded that the advanced geochemical model would be useful in predicting the Mn and Zn behavior during mine drainage treatment with Mn neutralization sludge. Graphical abstract: (Figure presented.).

DOI： 10.1007/s11270-024-07031-6

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記述言語：日本語  

記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.jece.2024.112053

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Institute of Metals  

DOI： 10.2320/matertrans.m-m2024808

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記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.2473/journalofmmij.139.52

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.apt.2023.104227

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記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.4164/sptj.60.600

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

DOI： 10.1007/s40831-023-00754-6

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その他リンク： https://link.springer.com/article/10.1007/s40831-023-00754-6/fulltext.html

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

Ciprofloxacin (CIP), a compound with bioaccumulation toxicity and antibiotic resistance, is frequently detected in water at alarming concentrations, which is becoming an increasing concern. In this study, a low-cost ceramsite was developed from industrial solid wastes through sintering to remove CIP from wastewater. The effects of adsorbent dosage, initial pH, contact time, initial CIP concentration, and temperature were explored. More than 99% of CIP (20–60 mg/L) was removed at around pH 2–4 by the ceramsite. The kinetic data fitted well with the pseudo-second-order model, revealing that chemisorption was the main rate-determining step. The isotherm data was better described by the Freundlich model, suggesting that CIP was removed by the formation of multiple layers on the heterogeneous surface. Moreover, the removal efficiency was practically higher than 95% during five regeneration cycles, when different regeneration methods were used, including calcination, HCl, and NaOH washing, indicating that the ceramsite exhibited outstanding reusability in removing CIP. The primary mechanism of CIP removal by the ceramsite was found to be the synergism of adsorption and flocculation, both of which depended on the release of Ca2+ from the ceramsite. In addition, strong Ca-CIP complexes could be formed through surface complexation and metal cation bridging between Ca2+ and different functional groups in CIP.

DOI： 10.3390/ijerph20065042

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記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

Cadmium (Cd), as a type of heavy metal, can increase the incidence of many diseases, even in low concentrations. In this study, tobermorite was hydrothermally synthesized and then applied to adsorb Cd2+ from an aqueous solution. The physicochemical characteristics of the synthesized tobermorite were detected, and the results indicated that the well-crystallized tobermorite had a lot of mesopores and a large specific surface area of 140.92 m2/g. It acquired a pH self-adjustment ability via spontaneously releasing Ca2+ and OH- into the aqueous solution. The effects of different factors on Cd2+ removal were investigated. For Cd2+, the removal efficiency could reach 99.71% and the maximum adsorption capacity was 39.18 mg/g using tobermorite. The adsorption data was best fitted with the pseudo-second-order kinetic and Langmuir isotherm models. In addition, there was no strict limit on the solution pH in Cd2+ adsorption because the tobermorite could adjust the solution pH to an alkaline atmosphere spontaneously. The efficient removal of Cd2+ using tobermorite was a result of surface complexation and ion exchange.

DOI： 10.3390/ma16031314

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

A passive treatment process using sulfate-reducing bacteria (SRB) is known to be effective in removing heavy metals from acid mine drainage (AMD), though there has been little discussion of the mechanism involved to date. In this work, a sulfate-reducing column test was carried out using supplementary ethanol as an electron donor for microorganisms, and the reaction mechanism was examined using geochemical modeling and X-ray absorption fine structure (XAFS) analysis. The results showed that Cu was readily removed from the AMD on the top surface of the column (0–0.2 m), while Zn and Cd depletion was initiated in the middle of the column (0.2–0.4 m), where sulfide formation by SRB became noticeable. Calculations by a developed geochemical model suggested that ethanol decomposition by aerobic microbes contributed to the reduction of Cu, while sulfide produced by SRB was the major cause of Zn and Cd removal. XAFS analysis of column residue detected ZnS, ZnSO4 (ZnS oxidized by atmospheric exposure during the drying process), and CuCO3, thus confirming the validity of the developed geochemical model. Based on these results, the application of the constructed geochemical model to AMD treatment with SRB could be a useful approach in predicting the behavior of heavy metal removal.

DOI： 10.3390/ma16030928

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掲載種別：研究論文（国際会議プロシーディングス）  

The recovery of carbon fiber (CF) from wasted carbon fiber reinforced plastic (CFRP) composites and the reuse of CF have been also required in the resource recycling. The previous study of recovery CF using the torrefaction reported that 15-50 % reduction in tensile strength of recovered CF compared to virgin CF. It is necessary to develop the recovery technology of CF from CFRP without reducing tensile strength of recovered CF. In this study, we evaluate the applicability of pulsed discharge with instantaneous high energy releases as a novel approach, which is already known to be effective in separating cathode particles from aluminum foil of lithium-ion batteries (LiBs) based on our previous investigation. The separation of cathode particles was caused in the interface between the foil and particles by deactivating adhesive strength of binder which connected these due to the Joule heating of the foil generated by the current of discharge. The object of this study is to applicate pulsed discharge to recover CF without attaching polymer matrix from laminated CFRP with delaminating CFRP layers by loading discharge horizontally. The tested sample sizes of laminated CFRP were 100 mm length, 30 mm width and 8 mm thickness. Two electrodes of pulsed discharge were set on the surface of sample, and the electrode gap was 50 mm. The pulsed discharge with conditions of capacitor capacity of 80 μF, charging voltage of 10 kV and charging energy in the capacitor of 4000 J was performed in the water. The CFRP layer was peeled, and fibers about 20 mm length were also recovered by the discharge. The scanning electron microscope (SEM) images for recovered fibers indicated that fibers were without the adhesion of matrix resin. It was assumed that the separation mechanism of resin from CFRP was that the insulation breakdown in resin was caused by the discharge, and the resin was removed by the plasmatization with high temperature, resulting in the recovery of CF. It is possible to consider that the volume expansion of resin induced by the plasmatization also caused the peeling of CFRP layer. The tensile strength of recovered CF was found to be 5.0 GPa by the single fiber tensile test and was 21 % less than that of the virgin one. These results indicated that pulsed discharge is effective in the recovery of CF from the laminated CFRP with the less tensile strength reduction of recovered CF.

DOI： 10.1109/PPC47928.2023.10310873

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掲載種別：研究論文（学術雑誌）   出版者・発行元：The Resources Processing Society of Japan  

DOI： 10.4144/rpsj.70.65

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Minerals  

Bioleaching of arsenic (As)-rich, so-called "dirty" concentrates can produce additional Cu value from the flotation waste while simultaneously releasing toxic As. This study bioleached three such concentrates of varying pyrite/enargite ratios ([Py]/[Ena] = 0.7, 1.3 and 2.4) at a pulp density of 20&#37;. The dissolution behavior of Cu and As in relation to the solution redox potential (Eh) was studied with and without activated carbon (AC) as a potential Eh-controlling catalyst. At this high pulp density, Eh was naturally suppressed, without a need for AC dosing, to <700 mV (a rapid pyrite dissolution is prevented in this Eh range). The effect of AC dosing on Eh varied depending on the type of concentrate; Eh was further reduced only in the case of the most enargite-rich concentrate, DC-I. Among the three concentrates, the highest Cu dissolution (35&#37;) was seen in DC-I (without AC dosing), which simultaneously achieved the lowest As solubilization. Arsenic was immobilized as amorphous precipitates, likely in a mixture of ferric arsenate, cupric arsenate, basic ferric sulfate and sulfur. Arsenic immobilization became increasingly ineffective as the pyrite content increased in the concentrate. Based on these results, setting a lower [Py]/[Ena] ratio prior to the dirty concentrate bioleaching could be a useful approach to promote Cu dissolution and As immobilization simultaneously.

DOI： 10.3390/min12040449

Web of Science

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記述言語：日本語   出版者・発行元：一般社団法人 環境資源工学会  

DOI： 10.4144/rpsj.68.124

CiNii Research

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/min11040432

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.hydromet.2020.105417

記述言語：その他   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.hydromet.2018.03.014

記述言語：その他   掲載種別：研究論文（その他学術会議資料等）  

DOI： 10.4028/www.scientific.net/SSP.262.273

開催年月日： 2023年6月

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Suitalbe Eh-lowering activated carbon in bioleaching of enargite concentrate

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Evaluation of the long-term chemical stability of adsorbed Hg on pyrite surfaces under various redox and pH conditions

開催年月日： 2022年10月 - 2022年11月

記述言語：英語   会議種別：口頭発表（一般）  

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記述言語：日本語   会議種別：口頭発表（招待・特別）  

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開催年月日： 2022年8月

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Effect of silver and activated carbon on enargite bioleaching using extremely acidophilic microorganisms

開催年月日： 2018年9月

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開催年月日： 2018年9月

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Carbon-assisted bioleaching of primary copper sulfides

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Comparison on the catalytic mechanism of activated carbon in bioleaching of chalcopyrite and enargite

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Carbon-assisted bioleaching of chalcopyrite concentrate

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Evaluation of catalytic effect of activated carbon on enargite bioleaching

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Catalytic effect of activated carbon on bioleaching of enargite concentrate

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Mechanism of silver-catalyzed bioleaching of enargite concentrate

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Investigating catalytic effect of silver on bioleaching of enargite concentrate

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Selective bioleaching of enargite (Cu3AsS4) over pyrite (FeS2) for Cu recovery

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