Publisher：AIP Conference Proceedings  

Electrochemical measurement is essential for hydrometallurgical process for evaluation oxidation and reduction reaction. However, electrochemical measurements for powder sample is not well developed since it is difficult to make powder sample electrode. Authors has developed new electrode system for micro gram order powder sample with relative simple method. This system can obtain high reproducibility and sensitivity compared with conventional electrode. Authors evaluates new powder electrode system for various sulfide mineral to apply various hydrometallurgical process. Powder sample indicated high resolution results which can obtain sharp peak, it can indicates oxidation process can be estimated in detail. This method can be applied not only hydrometallurgical process but also various mineral processing and water treatment system.

DOI： 10.1063/5.0237380

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Publisher：AIP Conference Proceedings  

Chalcopyrite is one of the major sources of copper minerals which is commonly separated from other gangue minerals using a flotation process. The floatability of chalcopyrite is one of the major factors for a successful beneficiation process. It was found that chalcopyrite's floatability is greatly reduced by ferric oxyhydroxide on its surface. On the other hand, ferric oxyhydroxide, such as goethite, is abundant in nature. Therefore, this study focuses on the floatability of chalcopyrite in the presence of goethite. The goethite in the form of nanoparticles was employed in this study. Goethite nanoparticles hindered chalcopyrite flotation in column-type flotation experiments. 30 mg/L goethite nanoparticles reduced chalcopyrite flotation recovery from 93% to 15%. This flotation result indicated that goethite nanoparticles can act as nanodepressant for chalcopyrite flotation. X-ray photoelectron analysis was employed to characterize the surface. Goethite nanoparticles were adsorbed on the surface of chalcopyrite, making the exterior of it hydrophilic, thus lowering the floatability.

DOI： 10.1063/5.0242889

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Publisher：AIP Conference Proceedings  

In recent years, the development of clean energy technologies increases the consumption of valuable metals, such as copper. To meet the increasing global demand for copper metal, mining operations process low grade copper ores containing various impurities, such as arsenic minerals. However, arsenic minerals reduce copper quality, cause environmental concerns, and improve operating costs. Therefore, it is important to separate the arsenic minerals from the copper minerals. There are various studies on the separation of arsenic minerals from other copper minerals. However, there is no discussion about the study of nanoparticles in the flotation of arsenic minerals. Therefore, this study examined the impact of nanoparticles on arsenic mineral flotation. Goethite nanoparticles and enargite were employed as nanoparticles and arsenic minerals, respectively. Micro-flotation tests were performed to evaluate the flotation behavior of enargite in the presence of goethite nanoparticles. The flotation results indicated that treatment with 30 mg/L and 50 mg/L goethite nanoparticles at pH 5 drastically reduced enargite recovery from 94% to 22% and 16%. The zeta potential of enargite increased as the quantity of goethite nanoparticles increased, indicating that goethite nanoparticles adsorb on the enargite surface. This study demonstrated that goethite nanoparticles have potential as a nanodepressant for enargite flotation.

DOI： 10.1063/5.0236697

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Publisher：AIP Conference Proceedings  

Iron oxide-hydroxide nanoparticles have high adsorption properties, and their crystalline structure has adsorption sites for water molecules. Owing to these properties, iron oxide-hydroxide nanoparticles has been reported to alter the surface hydrophobicity of chalcopyrite, depressing its floatability. However, there is no study available on the effect of iron oxide-hydroxide nanoparticles on bornite flotation. Therefore, this study examined iron oxide-hydroxide nanoparticles for their potential as a depressant of bornite. It was found that iron oxide nanoparticles acted as a depressant of bornite in flotation tests using pure mineral. Iron oxide-hydroxide nanoparticles hydrophilized the surface of bornite, suggesting the possibility of separation of bornite and other valuable associated sulfide minerals, such as molybdenite. Based on these results, the influence of iron oxide nanoparticles on the mixed flotation of bornite and molybdenite was investigated in the presence of potassium amyl xanthate and diesel oil as copper and molybdenum collectors. The separation efficiency between bornite and molybdenite was 61.5% after employing 30 mg/L of iron oxide-hydroxide as a depressant. Under this condition, molybdenite recovery was 94.9% and bornite recovery was 33.3%. This result demonstrates the potential use of iron oxide-hydroxide as a selective depressant for bornite in the selective flotation of copper-molybdenum.

DOI： 10.1063/5.0242887

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Publisher：AIP Conference Proceedings  

Copper plays an essential role in the development of renewable energy resources and the production of electric vehicles, which drive the increasing copper demand in the future. Copper is primarily extracted from copper sulfide ores which contain chalcopyrite and bornite as primary copper sulfide minerals and chalcocite as secondary copper sulfide minerals. However, these copper sulfides are associated with molybdenite. Sodium metabisulfite has been used to separate chalcopyrite and molybdenite in a selective flotation process. However, there is limited study focus on the effect of sodium metabisulfite on the separation of chalcocite and molybdenite using flotation. Therefore, this study investigates the effect of sodium metabisulfite on the floatability of chalcocite and molybdenite in the presence of various flotation collectors, i.e., xanthate, thionocarbamate, and mercaptan. The surface properties of chalcocite and molybdenite are studied by employing Fourier Transform Infrared Spectroscopy (FTIR). The flotation results show that sodium metabisulfite separated the molybdenite and chalcocite by depressing chalcocite flotation. In addition, the separation efficiency is higher if sodium metabisulfite was used for separating chalcocite and molybdenite that have been treated with thionocarbamate.

DOI： 10.1063/5.0236779

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Language：English   Publisher：The Japan Institute of Metals and Materials  

<p>This study investigated the effects of potassium amyl xanthate (KAX) and oxidation treatment using hydrogen peroxide (H₂O₂) on the selective flotation of copper concentrates containing arsenic-bearing copper minerals. The mineralogical analysis revealed that enargite and chalcopyrite were the main arsenic-bearing copper and copper sulfide minerals, respectively, in the copper concentrate. KAX treatment at pH 9 improved the recoveries of copper sulfide and arsenic-bearing copper minerals. However, arsenic-bearing copper minerals floated more rapidly than copper sulfide minerals, indicating better separation selectivity. The separation selectivity of the KAX treatment was significantly improved at pH 10. H₂O₂ treatment was found to selectively improve the recovery of arsenic-bearing copper minerals. A combination treatment using 0.1 M H₂O₂ and 60 g/t of KAX at pH 9 enhanced the separation selectivity in the selective flotation of copper sulfide and arsenic-bearing copper minerals by producing a copper concentrate with the lowest arsenic grade and highest copper grade in tailings compared to those obtained from separated KAX and H₂O₂ treatments.</p>

DOI： 10.2320/matertrans.m-m2023811

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Powder Technology  

Molybdenite is associated with primary and secondary copper sulfide minerals. Few studies have focused on the selective flotation of molybdenite to separate it from secondary copper sulfide minerals, such as chalcocite. This study evaluated the use of oxidation treatment to separate molybdenite from chalcocite. The effects of oxidation treatment with hydrogen peroxide (H2O2) on the flotation behaviors of molybdenite and chalcocite in the presence of collectors (i.e., potassium amyl xanthate and diesel oil) were evaluated, and the impacts of H2O2 concentration, oxidation treatment duration, and pH level were assessed. Chalcocite flotation tests showed that the H2O2 treatment significantly reduced the recovery of chalcocite due to the formation of copper hydroxide and sulfate species on the chalcocite surface, which altered its surface hydrophobicity. On the other hand, the low surface oxidation of molybdenite led to high flotation recovery after the oxidation treatment. Oxidation treatment with a 10 mM H2O2 solution at a pH of 9 for 20 min resulted in a separation efficiency of 87%, with 98% molybdenite recovery and 11% chalcocite recovery. The results show that H2O2 oxidation treatment enables the selective flotation of molybdenite to separate it from chalcocite.

DOI： 10.1016/j.powtec.2023.119078

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Advanced Powder Technology  

The main challenge for the selective flotation of copper and molybdenum (Cu-Mo) sulfide minerals in seawater is the formation of colloidal precipitates in strongly alkaline conditions. These precipitates hinder the selective separation of copper from molybdenum minerals in seawater by lowering the floatability of Cu-Mo sulfide minerals. The present study aimed to examine the direct utilization of seawater in the selective flotation of Cu-Mo sulfides. Additionally, the effectiveness of sodium metabisulfite (Na2S2O5) as a copper depressant for selective flotation of Cu-Mo sulfides in seawater was studied under weakly acidic, neutral, and moderately alkaline conditions. A complex Cu-Mo concentrate that largely consisted of chalcopyrite and molybdenite, as well as a tiny amount of pyrite and quartz, was used in the flotation tests. The flotation results revealed that treatment with 3.6 kg/t Na2S2O5 in seawater at pH 5.5 significantly lowered the copper recovery from 97% to 11% and caused a modest reduction in the molybdenum recovery from 98% to 94% with a Cu-Mo separation efficiency of 83%. These flotation results demonstrate that Na2S2O5 treatment in seawater selectively depresses the floatability of copper minerals. Consequently, molybdenum can be separated from copper minerals under a weakly acidic condition in seawater. In addition, this study discusses the effects of various pH conditions and dosages of Na2S2O5. The surface properties of Cu-Mo minerals were studied using X-ray photoelectron and infrared spectroscopies, and a mechanism to explain the selective flotation of Cu-Mo using Na2S2O5 treatment in seawater is proposed.

DOI： 10.1016/j.apt.2023.104258

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Journal of Environmental Chemical Engineering  

Chalcopyrite flotation is selectively depressed by oxidation treatment. The presence of ferric oxyhydroxide on the surface of chalcopyrite after oxidation treatment is a key factor in depressing chalcopyrite flotation. However, there is no concrete evidence that ferric oxyhydroxide has a depressing effect. In addition, the effectiveness of this depressing effect could be enhanced by directly applying ferric oxyhydroxide nanoparticles. This study investigated the effect of goethite (α-FeOOH) nanoparticles on the surface properties and flotation behavior of chalcopyrite. α-FeOOH nanoparticles were produced through chemical precipitation followed by hydrothermal treatment. The crystalline structure of irregular rice grain-shaped α-FeOOH nanoparticles was confirmed by the X-ray diffraction pattern and scanning electron microscope image. Micro-flotation experiments showed that chalcopyrite recovery decreased significantly from 93 % to 13 % when 30 mg/L α-FeOOH nanoparticles was used. This flotation result demonstrated the potential of α-FeOOH nanoparticles as a nanodepressant for the flotation of chalcopyrite. These nanoparticles physically adsorbed on the chalcopyrite surface and rendered its surface hydrophilic, thereby reducing the chalcopyrite flotation recovery. The attractive electrostatic force between the positively charged α-FeOOH nanoparticles and the negatively charged chalcopyrite surface is likely responsible for the adsorption of α-FeOOH nanoparticles on chalcopyrite.

DOI： 10.1016/j.jece.2023.110006

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：International Journal of Mining Science and Technology  

Enargite is typically associated with chalcocite. Owing to the similarity in the flotation behaviors of these minerals, both minerals are reported to concentrate in the conventional flotation circuit. However, inorganic arsenic in enargite can decrease the copper concentrate quality and increase the operating cost of processing this concentrate. Separating these minerals is important for cleaner copper production to avoid these effects. In this context, this study investigated the effect of hydrogen peroxide (H2O2) treatment on the flotation behavior of chalcocite and enargite. Flotation tests of pure and mixed minerals indicated that H2O2 treatment reduced the floatability of chalcocite and enargite by forming sulfate and copper hydroxide on their surfaces. Despite the detrimental effect of the H2O2 treatment, there was a narrow window of H2O2 concentration for separating both minerals, in which enargite floated and chalcocite was depressed. This selective flotation behavior was caused by the rapid adsorption of potassium amyl xanthate (KAX) and lower surface oxidation of enargite compared with that of chalcocite.

DOI： 10.1016/j.ijmst.2023.01.002

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>Effect of pH and precipitations on copper–molybdenum ore rougher flotation has been investigated in seawater with flotation experiments followed by precipitation estimation with thermodynamic calculations, turbidity measurements and XRD analysis. Results of flotation experiments in seawater indicated that the effect of pH on copper and molybdenum flotation maximum recovery seems limited. On the other hand, pH drastically influences copper and molybdenum flotation kinetic constant, it decreased a lot with increasing pH, and results of pH 8.5 and 9.0 is quite similar. From thermodynamic calculation, precipitation effect on seawater less than pH 9 seems limited since CaCO₃ and Mg(OH)₂ does not exist on this pH region. To estimate precipitation on pH in seawater, turbidity measurements were carried out with controlled pH and results indicated even pH is less than 9, noticeable turbidity can be seen. To confirm precipitation in seawater, precipitation was collected from controlled pH seawater solution. XRD analysis of precipitation indicated that obtained precipitation at pH 8.7 is CaCO₃, CaSO₄ and Mg(OH)₂. This result is not same as the result of thermodynamic calculation and it might be due to the activity coefficient and ionic strength effect. Although flotation kinetic is influenced with turbidity, turbidity influence on maximum recovery is limited. Effect of kinetic might be due to that precipitation exist as suspension and it prevent bubble and mineral attachments. Small effect of precipitation on maximum recovery might be due to exist of few precipitation on the surface of copper and molybdenum mineral since most of mineral in rougher flotation is gangue minerals and also most of precipitations might be on gangue minerals. These results indicated that seawater flotation have to take into account of precipitation effect more for flotation kinetic than maximum flotation recovery.</p>

DOI： 10.2320/matertrans.M-M2023805

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Powder Technology  

In the flotation of complex copper ores containing chalcopyrite in seawater, sodium metabisulfite (SMBS) has been widely used as a pyrite depressant. Here, calcium ions in seawater or in process water because of pH control using lime (CaO) or slaked lime (Ca(OH)2) can affect the floatability of chalcopyrite. However, the effect of SMBS on the floatability of chalcopyrite in the presence of calcium ions is unknown. Therefore, the current study investigated the flotation behavior and surface properties of chalcopyrite after treatment with SMBS in the absence and presence of Ca(OH)2. The flotation experiments demonstrated that both SMBS treatment and the addition of Ca(OH)2 exhibited a depressing effect on the natural floatability of chalcopyrite. This depressing effect of SMBS and Ca(OH)2 on the floatability of chalcopyrite was significantly decreased in the presence of potassium amyl xanthate (PAX). However, the combination of SMBS treatment and Ca(OH)2 formed calcium sulfite (CaSO3) on the surface of chalcopyrite, which significantly reduced the recovery of chalcopyrite from 97% to 66% when in the presence of PAX and at a pH of 9.

DOI： 10.1016/j.powtec.2022.117750

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Language：Japanese   Publisher：The Resources Processing Society of Japan  

<p>Arsenic removal from copper ores/concentrates is one of the most important issue in mining industries. Under the national project led by JOGMEC, Kyushu University and Sumitomo Metal Mining Co. Ltd. has carried out systematic research on the arsenic removal from copper concentrates, including the heat treatment-magnetic separation, flotation and bioleaching. The flotation studies were carried out mainly on chalcopyrite as a main copper sulfide and enargite as an arsenic containing copper sulfide. Enargite was separated from chalcopyrite by flotation by combining potassium amyl xanthate (PAX) and hydrogen peroxide. The resultant arsenic-rich “dirty” concentrates and/or arsenic-containing copper concentrates were subjected to the magnetic separation as well as bioleaching processes. After the heat treatment, chalcopyrite exhibited magnetic property whereas enargite did not. This difference enabled the magnetic separation of the two minerals. Bioleaching was carried out with the addition of activated carbon to improve the copper dissolution as well as As immobilization.</p>

DOI： 10.4144/rpsj.68.124

CiNii Research

Language：Others   Publishing type：Research paper (scientific journal)  

Sodium metabisulfite (MBS) was used in this study for selective flotation of chalcopyrite and molybdenite. Microflotation tests of single and mixed minerals were performed to assess the floatability of chalcopyrite and molybdenite. The results of microflotation of single minerals showed that MBS treatment significantly depressed the floatability of chalcopyrite and slightly reduced the floatability of molybdenite. The results of microflotation of mixed minerals demonstrated that the MBS treatment could be used as a selective chalcopyrite depressant in the selective flotation of chalcopyrite and molybdenite. Furthermore, the addition of diesel oil or kerosene could significantly improve the separation efficiency of selective flotation of chalcopyrite and molybdenite using MBS treatment. A mechanism based on X-ray photoelectron spectroscopy analysis results is proposed in this study to explain the selective depressing effect of MBS on the flotation of chalcopyrite and molybdenite.

DOI： 10.3390/min11121377

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The effect of sodium sulfite (Na2SO3) on the floatability of chalcopyrite and enargite was investigated in this work. The micro flotation tests of single and mixed minerals were performed under various concentrations of Na2SO3. The micro flotation tests of single minerals showed that Na2SO3 depressed the floatability of both minerals at pH 9 in the absence of potassium amyl xanthate (PAX). Interestingly, the addition of PAX followed by the Na2SO3 treatment selectively improved the recovery of enargite. On the other hand, the recovery of chalcopyrite remained low under a similar condition. The single mineral flotation results indicate that separation of chalcopyrite and enargite might be possible using PAX and Na2SO3 treatment. Indeed, the mixed mineral flotation results were in agreement with the flotation results of single minerals. The mineral surface was analyzed by X-ray photoelectron spectroscopy (XPS) after the treatments to explain the phenomenon. The XPS results show the presence of sulfate species on both mineral surfaces after the Na2SO3 treatment. The adsorbed PAX could prevent the formation of this sulfate species on the enargite surface and rendered the surface hydrophobic. However, the adsorbed PAX could not prevent the formation of sulfate species on the chalcopyrite surface and rendered the surface hydrophilic.

DOI： 10.1016/j.mineng.2021.107222

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The copper ore in Chilean copper porphyry deposits is often associated with molybdenum minerals. This copper–molybdenum (Cu–Mo) sulfide ore is generally mined from various locations in the mining site; thus, the mineral composition, oxidation degree, mineral particle size, and grade vary. Therefore, in the mining operation, it is common to blend the ores mined from various spots and then process them using flotation. In this study, the floatability of five types of Cu–Mo ores and the blending of these ores in seawater was investigated. The oxidation degree of these Cu–Mo ores was evaluated, and the correlation between flotation recovery and oxidation degree is presented. Furthermore, the flotation kinetics of each Cu–Mo ore were calculated based on a mineralogical analysis using mineral liberation analysis (MLA). A mineralogical prediction model was proposed to estimate the flotation behavior of blended Cu–Mo ore as a function of the flotation behavior of each Cu–Mo ore. The flotation results show that the recovery of copper and molybdenum decreased with the increasing copper oxidization degree. In addition, the recovery of blended ore can be pre-dicted via the flotation rate equation, using the maximum recovery (Rmax) and flotation rate coeffi-cient (k) determined from the flotation rate analysis of each ore before blending. It was found that Rmax and k of the respective minerals slightly decreased with increasing the degree of copper oxida-tion. Moreover, Rmax varied greatly depending on the mineral species. The total copper and molybdenum recovery were strongly affected by the degree of copper oxidation as the mineral fraction in the ore varied greatly depending upon the degree of oxidation.

DOI： 10.3390/min11080869

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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.

DOI： 10.1016/j.mineng.2020.106536

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1016/j.mineng.2020.106371

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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&#37; of molybdenite can be recovered as froth and 93&#37; 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.

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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.

Language：English   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1016/j.colsurfa.2018.06.029

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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.

DOI： 10.1016/j.mineng.2018.02.005

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Sodium hydrogen sulfide (NaHS) is commonly used as a copper depressant in the selective flotation of copper and molybdenum ores. However, the process is facing health and safety issues because NaHS readily yields toxic hydrogen sulfide gas (H2S) under acidic conditions. In this study, Na2SO3 was proposed as an alternative copper depressant. The effect of Na2SO3 on the surface wettability and floatability of chalcopyrite and molybdenite—typical copper and molybdenum minerals, respectively—was intensively studied using contact angle measurements and flotation tests. Contact angle readings show that the chalcopyrite surface became hydrophilic after the Na2SO3 treatment. Meanwhile, the molybdenite surface was relatively more hydrophobic compared with that of chalcopyrite after the treatment. Flotation tests using pure minerals of chalcopyrite and molybdenite demonstrate that the floatability of chalcopyrite decreased with increasing concentration of Na2SO3. On the other hand, the floatability of molybdenite gradually increased under similar conditions, suggesting that Na2SO3 might have the potential to be used for selective flotation of chalcopyrite and molybdenite. A possible mechanism is proposed in this study to explain the phenomenon using X-ray photoelectron spectroscopy analysis.

DOI： 10.3390/min8040172

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Seawater has been reported to depress the floatability of molybdenum in copper-molybdenum (Cu-Mo) flotation circuits under alkaline conditions (pH > 9.5). However, the seawater used in the process contains various minerals and flotation reagents, which make it difficult to investigate the depression mechanism. This paper presents a fundamental study into the effect of artificial seawater as a seawater model solution on the floatability of molybdenite and chalcopyrite, which are the main minerals in the Cu-Mo flotation process. Floatability tests in the absence of flotation reagents (i.e., frothers and collectors) reveal that artificial seawater adversely affects the floatability of molybdenite and chalcopyrite at pH > 9. This phenomenon can be attributed to the adsorption of hydrophilic Mg(OH)2 precipitates formed under alkaline conditions on the mineral surfaces, which increases the surface wettability of the mineral particles, as shown by contact angle measurements and atomic force microscopy (AFM) images. The effect of kerosene as a molybdenite collector has also been investigated to assess its potential in the selective flotation of molybdenite and chalcopyrite in artificial seawater.

DOI： 10.1016/j.mineng.2017.10.004

Language：Others   Publishing type：Research paper (other academic)  

Various oxidation treatments (i.e., plasma, and ozone) have been applied to separate molybdenite from other sulfide metals. However, plasma and ozone treatments exhibit stronger oxidation on chalcopyrite and molybdenite, reducing the separation selectivity of both minerals in flotation tests. On the other hand, hydrogen peroxide (H2O2) is frequently used as an oxidizing agent in wastewater treatment. It has also been reported to reduce the recovery of sulfide minerals. Therefore, the effect of H2O2 on separation of chalcopyrite and molybdenite was investigated in this study. Contact angle readings and surface images using atomic force microscopy (AFM) showed that chalcopyrite surface was more sensitive to surface oxidation compared to that of molybdenite in H2O2 aqueous solution. The floatability test of single mineral confirmed the contact angle results and AFM images, indicating a possibility for selective separation of chalcopyrite and molybdenite using a H2O2 aqueous solution. In addition, iron was used to improve the oxidation performance of H2O2 and its effect on the selective flotation of chalcopyrite and molybdenite is intensively studied in this work.

Language：Others   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.2320/matertrans.M-M2017807

Language：Others   Publishing type：Research paper (scientific journal)  

The selective flotation of chalcopyrite (CuFeS2) and molybdenite (MoS2) was studied using surface oxidation treatments (i.e., ozone (O3) and hydrogen peroxide (H2O2)). The results indicated that the oxidation treatments had different effects on the wettability of chalcopyrite and molybdenite. Single mineral flotation results showed that the H2O2 treatment had higher separation selectivity for molybdenite and chalcopyrite compared with that of the ozone treatment. The contact angle measurement and X-ray photoelectron spectroscopy (XPS) analysis results showed that the chalcopyrite surface became hydrophilic owing to the surface deposition of oxidized iron and copper after the H2O2 treatment. On the other hand, the contact angle of molybdenite slightly increased following the H2O2 treatment at high concentrations. Possible mechanisms of this phenomenon were proposed in this work. Moreover, the separation selectivity of each oxidation method was discussed. Flotation tests using bulk Cu-Mo concentrate showed that H2O2 could deliver a flotation result comparable to conventional Cu-Mo flotation using NaHS.

DOI： 10.1016/j.mineng.2016.10.007

Language：Others   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1016/j.mineng.2016.06.023

Language：Others   Publishing type：Research paper (other academic)  

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.

Language：Others   Publishing type：Research paper (other academic)  

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.

Language：Others   Publishing type：Research paper (scientific journal)  

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.

DOI： 10.1016/j.colsurfa.2016.04.039

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