In this work,the growth of copper sulfide crystal onto azurite surfaces during sulfurization and its response to flotation are investigated.Filed emission scanning electron microscopy-energy dispersive X-ray spectrosc...In this work,the growth of copper sulfide crystal onto azurite surfaces during sulfurization and its response to flotation are investigated.Filed emission scanning electron microscopy-energy dispersive X-ray spectroscopy(FESEM) and X-ray diffraction(XRD) studies confirmed that the sulfurization of azurite is not limited to the mineral surface,but rather penetrates into the bulk to form covellite crystal(synCuS),creating favorable conditions for the stable adsorption of xanthate and greatly promoting the azurite flotation.Additionally,as demonstrated by X-ray photoelectron spectroscopy(XPS) and time of flight secondary ion mass spectrometry(TOF-SIMS) analyses,a redox reaction occurred during this process,and Cu(Ⅱ) onto the mineral surface was reduced to Cu(Ⅰ).Correspondingly,reduced S^(2-) was oxidized to(S_(2))^(2-),(S_n)^(-2),and even to deeper oxidation state S~0,(S_(x)O_(y))^(n-) and SO_(4)^(2-).Excess sodium sulfide strengthens copper sulfide to form onto the azurite surface,and provides enough raw material for crystal copper sulfide to grow,resulting in the formation of "flake-like" covellite with a better crystallinity.However,the floatability of azurite decreased dramatically under this condition,because the generated massive colloidal copper sulfide in flotation pulp deteriorates the flotation environment,resulting in a decreased effective adsorption of collector onto azurite surfaces.展开更多
Many researchers found that the Fe2+together with less amount of Cu2+can accelerate the leaching of chalcopyrite.In this work,the leaching of chalcopyrite with Cu2+was investigated.The leaching residuals were examined...Many researchers found that the Fe2+together with less amount of Cu2+can accelerate the leaching of chalcopyrite.In this work,the leaching of chalcopyrite with Cu2+was investigated.The leaching residuals were examined by Raman spectroscopy.Based on the leaching experiments,the chemical equilibrium in solution was calculated using Visual MINTEQ.The results showed that the Fe in chalcopyrite lattice was replaced by Cu2+;therefore,the chalcopyrite transformed into covellite.Furthermore,the formation of chalcocite occurred when Fe2+and Fe3+were added to the solution containing Cu2+.The copper extraction increased with a decrease of the initial redox potential(or the ratio of Fe3+/Fe2+).展开更多
In this work,the bioleaching process of pyrite,chalcocite and covellite which were the main phase compositions for Zijin copper mineral was comprehensively studied.The influence parameters,such as leaching temperature...In this work,the bioleaching process of pyrite,chalcocite and covellite which were the main phase compositions for Zijin copper mineral was comprehensively studied.The influence parameters,such as leaching temperature,Fe^(3+)concentration,pH of solution and bacteria concentration were investigated.The leaching kinetics of the pyrite,chalcocite and covellite under the studied conditions was successfully modeled by an empirical diffusion-like equation,respectively.The apparent activity energy of pyrite leaching,chalcocite leaching(stage Ⅱ)and covellite leaching was calculated to be 69.29,65.02 and 84.97 kJ/mol,respectively.展开更多
A large volume of bacterially produced precipitates are generated during the bio-treatment of heavy metal wastewater.The composition of the bacterially produced precipitates and its effects on sulfate reducing bacteri...A large volume of bacterially produced precipitates are generated during the bio-treatment of heavy metal wastewater.The composition of the bacterially produced precipitates and its effects on sulfate reducing bacteria (SRB) in copper-containing waste stream were evaluated in this study.The elemental composition of the microbial precipitate was studied using electrodispersive X-ray spectroscopy (EDX),and it was found that the ratio of S:Cu was 1.12.Combining with the results of copper distribution in the SRB metabolism culture,which was analyzed by the sequential extraction procedure,copper in the precipitates was determined as covellite (CuS).The bacterially produced precipitates caused a decrease of the sulfate reduction rate,and the more precipitates were generated,the lower the sulfate reduction rate was.The particle sizes of bacterially generated covellite were ranging from 0.03 to 2 m by particles size distribution (PSD) analysis,which was smaller than that of the SRB cells.Transmission electron microscopy (TEM) analysis showed that the microbial covellite was deposited on the surface of the cell.The effects of the microbial precipitate on SRB metabolism were found to be weakened by increasing the precipitation time and adding microbial polymeric substances in later experiments.These results provided direct evidence that the SRB activity was inhibited by the bacterially produced covellite,which enveloped the bacterium and thus affected the metabolism of SRB on mass transfer.展开更多
The bioleaching of bornite with mixed moderately thermophilic culture at 50 °C was investigated. The intermediary species formed during the leaching of bornite were characterized by XRD and XPS. In addition, the ...The bioleaching of bornite with mixed moderately thermophilic culture at 50 °C was investigated. The intermediary species formed during the leaching of bornite were characterized by XRD and XPS. In addition, the evolution of Cu-state during leaching of bornite was further studied by applying φh–p H diagram and cyclic voltammetry. The results showed that the bornite was more likely to be leached at high redox potential. Furthermore, the intermediary sulfides, such as isocubanite, covellite, chalcopyrite, disulfide, and polysulfide, were formed in the course of bornite dissolution. The Cu 2 p photoelectron spectrum revealed that the valence of copper in bornite and intermediary sulfide formed in the dissolution of bornite is ＋1. The bornite and chalcopyrite can be converted into each other, and both can be further converted to covellite and/or chalcocite.展开更多
The surface characteristics,collector adsorption,and flotation response of covellite in the presence of NaClO and FeCl_(3) were investigated using micro-flotation tests,X-ray photoelectron spectroscopy(XPS),time-of-fl...The surface characteristics,collector adsorption,and flotation response of covellite in the presence of NaClO and FeCl_(3) were investigated using micro-flotation tests,X-ray photoelectron spectroscopy(XPS),time-of-flight secondary ion mass spectrometry(TOF-SIMS),and contact angle measurements.The micro-flotation test results indicated that covellite was effectively inhibited by the presence of NaClO and FeCl_(3).However,the dosages of these depressants were large,and the conditioning time was long.The results of the XPS and TOF-SIMS analyses indicated that NaClO could oxidize the covellite surface and reduce the active sites of Cu.Oxidation products,including CuO and Cu(OH)_(2),were generated on the covellite surface.After the addition of FeCl_(3),the precipitation of iron hydroxide on the covellite surface increased the content of hydrophilic species on the mineral surface.Thus,the adsorption of ammonium dibutyl dithiophosphate on covellite surface was prevented,which reduced the floatability of the covellite.展开更多
Electrochemical characteristics of covellite (CuS) are of importance from flotation and metallurgical point of view, as well as due to its potential application in solid state solar cells and in photocatalytic reactio...Electrochemical characteristics of covellite (CuS) are of importance from flotation and metallurgical point of view, as well as due to its potential application in solid state solar cells and in photocatalytic reactions. Also, the compound CuS appears as an intermediary product or a final product in electrochemical oxidation reactions of chalcocite (Cu2S) which exhibits supercapacitor characteristics. Natural copper mineral covellite has been investigated in inorganic sulfate acid electrolytes, as well as in strong alkaline electrolyte. Physical properties of covellite were characterized by X-ray diffraction (XRD) and the active surface was examined by optical and electron microscopy (EM) before and after oxidation in galvanostatic regime. Different electrochemical methods (galvanostatic, potentiostatic, cyclic voltammetry and electrochemical impedance spectroscopy - EIS) have been used. The capacitance of around 21 Fcm-2 (geometric area), serial resistance of about 90 Ωcm2 and leakage resistance of about 1200 Ωcm2 have been measured in 1 M H2SO4. The addition of cupric ions in sulfate electrolyte leads to the significant increasing of the capacitance, but having the increase of self-discharge as a negative side phenomenon. The capacitance of around 6.7 Fcm-2 (geometric area), serial resistance of about 80 Ωcm2 and leakage resistance of about 380 Ωcm2 have been measured in 6 M KOH.展开更多
基金supported by the National Natural Science Foundation of China (No. 52074138)Basic research project of Yunnan Province (No. 202001AS070030)Open Foundation of State Key Laboratory of Mineral Processing (BGRIMM-KJSKL2020-03)。
文摘In this work,the growth of copper sulfide crystal onto azurite surfaces during sulfurization and its response to flotation are investigated.Filed emission scanning electron microscopy-energy dispersive X-ray spectroscopy(FESEM) and X-ray diffraction(XRD) studies confirmed that the sulfurization of azurite is not limited to the mineral surface,but rather penetrates into the bulk to form covellite crystal(synCuS),creating favorable conditions for the stable adsorption of xanthate and greatly promoting the azurite flotation.Additionally,as demonstrated by X-ray photoelectron spectroscopy(XPS) and time of flight secondary ion mass spectrometry(TOF-SIMS) analyses,a redox reaction occurred during this process,and Cu(Ⅱ) onto the mineral surface was reduced to Cu(Ⅰ).Correspondingly,reduced S^(2-) was oxidized to(S_(2))^(2-),(S_n)^(-2),and even to deeper oxidation state S~0,(S_(x)O_(y))^(n-) and SO_(4)^(2-).Excess sodium sulfide strengthens copper sulfide to form onto the azurite surface,and provides enough raw material for crystal copper sulfide to grow,resulting in the formation of "flake-like" covellite with a better crystallinity.However,the floatability of azurite decreased dramatically under this condition,because the generated massive colloidal copper sulfide in flotation pulp deteriorates the flotation environment,resulting in a decreased effective adsorption of collector onto azurite surfaces.
基金Project(2016RS2016)supported by the Hunan Provincial Science and Technology Leader(Innovation Team of Interface Chemistry of Efficient and Clean Utilization of Complex Mineral Resources),ChinaProject supported by the Co-Innovation Centre for Clean and Efficient Utilization of Strategic Metal Mineral Resources,ChinaProject(2015CX005)supported by the Innovation Driven Plan of Central South University,China
文摘Many researchers found that the Fe2+together with less amount of Cu2+can accelerate the leaching of chalcopyrite.In this work,the leaching of chalcopyrite with Cu2+was investigated.The leaching residuals were examined by Raman spectroscopy.Based on the leaching experiments,the chemical equilibrium in solution was calculated using Visual MINTEQ.The results showed that the Fe in chalcopyrite lattice was replaced by Cu2+;therefore,the chalcopyrite transformed into covellite.Furthermore,the formation of chalcocite occurred when Fe2+and Fe3+were added to the solution containing Cu2+.The copper extraction increased with a decrease of the initial redox potential(or the ratio of Fe3+/Fe2+).
基金Project(51574036)supported by the National Natural Science Foundation of China。
文摘In this work,the bioleaching process of pyrite,chalcocite and covellite which were the main phase compositions for Zijin copper mineral was comprehensively studied.The influence parameters,such as leaching temperature,Fe^(3+)concentration,pH of solution and bacteria concentration were investigated.The leaching kinetics of the pyrite,chalcocite and covellite under the studied conditions was successfully modeled by an empirical diffusion-like equation,respectively.The apparent activity energy of pyrite leaching,chalcocite leaching(stage Ⅱ)and covellite leaching was calculated to be 69.29,65.02 and 84.97 kJ/mol,respectively.
基金supported by the National Natural Science Foundation of China(20877075)National Key Technologies R&D Program(2006BAC02A05)National Basic Research Program of China(2007CB613501)
文摘A large volume of bacterially produced precipitates are generated during the bio-treatment of heavy metal wastewater.The composition of the bacterially produced precipitates and its effects on sulfate reducing bacteria (SRB) in copper-containing waste stream were evaluated in this study.The elemental composition of the microbial precipitate was studied using electrodispersive X-ray spectroscopy (EDX),and it was found that the ratio of S:Cu was 1.12.Combining with the results of copper distribution in the SRB metabolism culture,which was analyzed by the sequential extraction procedure,copper in the precipitates was determined as covellite (CuS).The bacterially produced precipitates caused a decrease of the sulfate reduction rate,and the more precipitates were generated,the lower the sulfate reduction rate was.The particle sizes of bacterially generated covellite were ranging from 0.03 to 2 m by particles size distribution (PSD) analysis,which was smaller than that of the SRB cells.Transmission electron microscopy (TEM) analysis showed that the microbial covellite was deposited on the surface of the cell.The effects of the microbial precipitate on SRB metabolism were found to be weakened by increasing the precipitation time and adding microbial polymeric substances in later experiments.These results provided direct evidence that the SRB activity was inhibited by the bacterially produced covellite,which enveloped the bacterium and thus affected the metabolism of SRB on mass transfer.
基金Project(2016RS2016) supported by the Hunan Provincial Science and Technology Leader(Innovation Team of Interface Chemistry of Efficient and Clean Utilization of Complex Mineral Resources),ChinaProject supported by the Co-innovation Centre for Clean and Efficient Utilization of Strategic Metal Mineral Resources,ChinaProject(2015CX005) supported by the Innovation Driven Plan of Central South University,China
文摘The bioleaching of bornite with mixed moderately thermophilic culture at 50 °C was investigated. The intermediary species formed during the leaching of bornite were characterized by XRD and XPS. In addition, the evolution of Cu-state during leaching of bornite was further studied by applying φh–p H diagram and cyclic voltammetry. The results showed that the bornite was more likely to be leached at high redox potential. Furthermore, the intermediary sulfides, such as isocubanite, covellite, chalcopyrite, disulfide, and polysulfide, were formed in the course of bornite dissolution. The Cu 2 p photoelectron spectrum revealed that the valence of copper in bornite and intermediary sulfide formed in the dissolution of bornite is ＋1. The bornite and chalcopyrite can be converted into each other, and both can be further converted to covellite and/or chalcocite.
基金the National Natural Science Foundation of China(No.51804080).
文摘The surface characteristics,collector adsorption,and flotation response of covellite in the presence of NaClO and FeCl_(3) were investigated using micro-flotation tests,X-ray photoelectron spectroscopy(XPS),time-of-flight secondary ion mass spectrometry(TOF-SIMS),and contact angle measurements.The micro-flotation test results indicated that covellite was effectively inhibited by the presence of NaClO and FeCl_(3).However,the dosages of these depressants were large,and the conditioning time was long.The results of the XPS and TOF-SIMS analyses indicated that NaClO could oxidize the covellite surface and reduce the active sites of Cu.Oxidation products,including CuO and Cu(OH)_(2),were generated on the covellite surface.After the addition of FeCl_(3),the precipitation of iron hydroxide on the covellite surface increased the content of hydrophilic species on the mineral surface.Thus,the adsorption of ammonium dibutyl dithiophosphate on covellite surface was prevented,which reduced the floatability of the covellite.
基金The authors gratefully acknowledge financial support from the Ministry of Education and Science,Government of the Republic of Serbia through the Project No.172 060:“New approach to designing materials for energy conversion and storage”.
文摘Electrochemical characteristics of covellite (CuS) are of importance from flotation and metallurgical point of view, as well as due to its potential application in solid state solar cells and in photocatalytic reactions. Also, the compound CuS appears as an intermediary product or a final product in electrochemical oxidation reactions of chalcocite (Cu2S) which exhibits supercapacitor characteristics. Natural copper mineral covellite has been investigated in inorganic sulfate acid electrolytes, as well as in strong alkaline electrolyte. Physical properties of covellite were characterized by X-ray diffraction (XRD) and the active surface was examined by optical and electron microscopy (EM) before and after oxidation in galvanostatic regime. Different electrochemical methods (galvanostatic, potentiostatic, cyclic voltammetry and electrochemical impedance spectroscopy - EIS) have been used. The capacitance of around 21 Fcm-2 (geometric area), serial resistance of about 90 Ωcm2 and leakage resistance of about 1200 Ωcm2 have been measured in 1 M H2SO4. The addition of cupric ions in sulfate electrolyte leads to the significant increasing of the capacitance, but having the increase of self-discharge as a negative side phenomenon. The capacitance of around 6.7 Fcm-2 (geometric area), serial resistance of about 80 Ωcm2 and leakage resistance of about 380 Ωcm2 have been measured in 6 M KOH.
