The lime-Cu^(2+)-xanthate process is commonly used for the flotation separation of sphalerite from pyrite.In this process,lime is added to the pulp to inhibit the floatability of pyrite.However,the excessive use of li...The lime-Cu^(2+)-xanthate process is commonly used for the flotation separation of sphalerite from pyrite.In this process,lime is added to the pulp to inhibit the floatability of pyrite.However,the excessive use of lime can result in pipeline blockage and inadequate recovery of associated precious metals.Therefore,it is necessary to develop new flotation process that minimizes or eliminates the use of lime.In this paper,a novel Fe^(3+)-Cu^(2+)-butyl xanthate process was developed as an alternative to lime for separating of sphalerite from pyrite.The flotation results indicated that with the artificially-mixed minerals,the flotation recovery of pyrite was lower than 16%and that of sphalerite was higher than 47%at pH 5.0−10.0.The zeta potential measurements revealed that ferric ion preferred to adsorb on pyrite,and copper ion displaced with zinc ion from the lattice at the interface of sphalerite.The wettability analyses indicated that the hydrophobicity of sphalerite surface increased apparently after being treated with Fe^(3+)-Cu^(2+)-BX,while the hydrophobicity of pyrite surface remained nearly unchanged.With XPS analysis,Cu-S bond and hydrophilic ferric hydroxide were detected separately on the surface of sphalerite and pyrite after conditioning with Fe^(3+)-Cu^(2+)-BX,which facilitated the flotation separation of sphalerite from pyrite with butyl xanthate collector.展开更多
In order to selectively separate chalcopyrite from pyrite,the effect of organic depressant lignosulfonate calcium(LSC) on the flotation separation of chalcopyrite from pyrite was investigated by flotation tests. The d...In order to selectively separate chalcopyrite from pyrite,the effect of organic depressant lignosulfonate calcium(LSC) on the flotation separation of chalcopyrite from pyrite was investigated by flotation tests. The depression mechanism was studied by Fourier-transform-infrared(FTIR) analysis. The flotation tests of single mineral show that LSC can depress the flotation of pyrite in a certain pH range,but it has little effect on chalcopyrite flotation. Flotation separation of a mixture of chalcopyrite and pyrite can be completed to obtain a copper concentrate grade up to 24.73% with a recovery of 80.36%. IR analysis shows that LSC and butyl xanthate compete in absorption on pyrite surface,and there exists an LSC characteristic peak on pyrite surface. There is little adsorption of LSC on chalcopyrite.展开更多
The interaction mechanism of collector DLZ in the flotation process of chalcopyrite and pyrite was investigated through flotation experiments,zeta potential measurements and infrared spectrum analysis.Flotation test r...The interaction mechanism of collector DLZ in the flotation process of chalcopyrite and pyrite was investigated through flotation experiments,zeta potential measurements and infrared spectrum analysis.Flotation test results indicate that DLZ is the selective collector of chalcopyrite.Especially,the recovery of chalcopyrite is higher than 90% in neutral and weak alkaline systems,while the recovery of pyrite is less than 10%.When using CaO as pH regulator,at pH=7-11,the floatability of pyrite is depressed and the recovery is less than 5%.Zeta potential analysis shows that the zeta potential of chalcopyrite decreases more obviously than that of pyrite after interaction with DLZ,confirming that collector DLZ shows selectivity to chalcopyrite and pyrite.And FTIR results reveal that the flotation selectivity of collector DLZ is due to chemical absorption onto chalcopyrite surface and only physical absorption onto pyrite surface.展开更多
In this paper,Sulfobacillus thermosulfidooxidans ST was selected for use in bioleaching of pyrite and chalcopyrite.The adsorption experiments revealed that more cells were adsorbed on the surface of pyrite than on the...In this paper,Sulfobacillus thermosulfidooxidans ST was selected for use in bioleaching of pyrite and chalcopyrite.The adsorption experiments revealed that more cells were adsorbed on the surface of pyrite than on the surface of chalcopyrite.The role of extracellular DNA(eDNA)in the bioleaching process was investigated by depletion of eDNA using DNase I.The number of cells attached on the chalcopyrite and pyrite surfaces decreased on a large scale,and the lag phase of cell growth increased,causing the leaching percentages of pyrite and chalcopyrite to decrease by approximately 11.6%and 20.5%,respectively.The formation and distribution of eDNA secreted during bioleaching was assessed by a fluorescent dye-based method and visualized by confocal laser scanning microscopy(CLSM).The content of eDNA increased with bioleaching time.Furthermore,ST showed a stronger capacity to produce eDNA on the surface of pyrite than on the surface of chalcopyrite.These results showed that the removal of eDNA has a more significant effect on the bioleaching of chalcopyrite than on pyrite.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
The flotation tests and XPS analyses on galena,sphalerite and pyrite have been carried out in a collecting-depressing-reactivating system(hereafter referred as the CDR system).In this system,sulfide minerals were firs...The flotation tests and XPS analyses on galena,sphalerite and pyrite have been carried out in a collecting-depressing-reactivating system(hereafter referred as the CDR system).In this system,sulfide minerals were first collected and activated by the collector,and then depressed strongly by Ca(OH)2 in the strong alkaline solution,and finally reactivated by H2SO4.The flotation tests of pure minerals show that in this system the flotation behaviors of sphalerite and pyrite present irreversible characteristics along with the change of pulp potential.Furthermore,through the CDR system,considerable differences in the flotabilities between galena and sphalerite/pyrite are also observed.The XPS analysis results for galena,sphalerite and pyrite in a CDR system show that in the strong alkaline solution,some of the collectors,that have been already adsorbed on the mineral surface in the collecting process,are desorbed by Ca(OH)2.The XPS analysis results also show that in H2SO4 reactivating process,the surface hydroxides of galena are desorbed again by H2SO4 and replaced by diethyl dithiocarbamate,but those of sphalerite and pyrite are not desorbed.This flotation system may be applied to the bulk-differential flotation process of sulfur-bearing low-grade lead-zinc ores.展开更多
Simulated heap bioleaching of low-grade high pyrite-bearing chalcocite ore was conducted at 40 °C with aeration of CO_2 and N_2.Ore samples were collected at day 43,64,85,106 and subjected to microbial community ...Simulated heap bioleaching of low-grade high pyrite-bearing chalcocite ore was conducted at 40 °C with aeration of CO_2 and N_2.Ore samples were collected at day 43,64,85,106 and subjected to microbial community analysis by 16S rRNA gene clone library.Phylogenetic analyses of 16S rDNA fragments revealed that the retrieved sequences are mainly related to genus Acidithiobacillus,Leptospirillum and Sulfobacillus.Aeration of CO_2 and N_2 significantly impacted the microbial community composition.When CO_2 was aerated,the proportion of genus Acidithiobacillus considerably increased,whereas the proportion of genus Leptospirillum and genus Sulfobacillus declined.However,with the aeration of N_2,the proportion of genus Acidithiobacillus and Leptospirillum increased,but genus Sulfobacillus decreased.When there was no aeration,the microbial community was similar to the inocula with the proportion of genus Leptospirillum mounted.These results indicated that the limitation of oxygen could change the bioleaching microbial community and the aeration of CO_2 and N_2 was favourable for the growth of sulfur-oxidizer(At.caldus) and iron-oxidizer(L.ferriphilum) respectively,which could be used for the regulation of microorganisms' role in mineral bioleaching.展开更多
The electrode process of pyrite in diethyldithiocarbamate (DDTC) solution pH 11.4 was investigated by using cyclic voltammetry, potentiost atic and chronopotentiometry. Tetraethylthioram disulphide(TETD) was electrode...The electrode process of pyrite in diethyldithiocarbamate (DDTC) solution pH 11.4 was investigated by using cyclic voltammetry, potentiost atic and chronopotentiometry. Tetraethylthioram disulphide(TETD) was electrodepo sited on pyrite electrode surface as the electrode potential is higher than 0.2 V. The relationship of the current density caused by diffusion and reaction time can be ascertained as i =1/(9.08×10 -5 +4.77×10 -3 t 0.5 ) , and the diffusion coefficient of DDTC on pyrite surface is about 3.72×10 - 6 cm 2/s. At pH 11.4, the thickness of TETD adsorbed on pyr ite surface is about 1.63 molecule layer. The electrochemical dynamics equation of the reduction of TETD on pyrite surface is given as η =0.116-0.064log[1- ( t/τ ) 0.5 ]. The kinetic parameters were determined as follows: the ex change current density ( i 0) is 3.08 μA/cm 2; the transmission coeffi cient( α ) is 0.462.展开更多
The role of CaCl2 during the high temperature chloridizing-reduction roasting process was investigated, aiming at acquiring high strength blast furnace burden with high iron grade and low nonferrous metals content. Th...The role of CaCl2 during the high temperature chloridizing-reduction roasting process was investigated, aiming at acquiring high strength blast furnace burden with high iron grade and low nonferrous metals content. The effects of CaCl2 dosage on pelletizing, preheating and reduction were investigated. The results show that CaCl2 can improve the wet drop strength but reduces the thermostability of pyrite cinder green balls. When the dosage of CaCl2 exceeds 1%, the compressive strength of preheated pellets decreases while the growth of iron oxide particles is improved. Furthermore, the compressive strength of pre-reduced pellets increases but the metallization degree of pre-reduced pellets decreases with CaCl2 additive. The removal tests indicate that Zn can be removed completely without CaCl2 additive, Cu is removed only under the condition with CaCl2 additive and part of Pb must be removed by CaCl2 additive.展开更多
Well-crystallized hexagonal hematite （α-Fe2O3） platelets were synthesized by hydrothermal process, using a highly concentrated ferric hydroxide as precursor. The precursor was prepared by adding ammonia to the ferr...Well-crystallized hexagonal hematite （α-Fe2O3） platelets were synthesized by hydrothermal process, using a highly concentrated ferric hydroxide as precursor. The precursor was prepared by adding ammonia to the ferric sulfate solution which was obtained by leaching pyrite cinders with sulfuric acid. Structure and morphology of the synthesized products were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope and selected area electron diffraction. The results reveal that the reaction temperature has significant effects on the structure, size and shape of the synthesized hematite particles. Typical hexagonal hematite platelets, about 0.4-0.6 μm in diameter and 0.1 μm in thickness, were prepared at 230 ℃ for 0.5 h. Al^3＋, contained in the sulfuric acid leaching solution as an impurity, plays an extremely important role in the formation of hexagonal hematite. In addition, a possible mechanism about the formation of hexagonal hematite platelets was proposed.展开更多
Various incorporation of Au in pyrite and its effects on the geometrical structure,electronic structure and flotability of pyrite were theoretically investigated and fully discussed by performing density functional th...Various incorporation of Au in pyrite and its effects on the geometrical structure,electronic structure and flotability of pyrite were theoretically investigated and fully discussed by performing density functional theory(DFT).The calculated incorporation energy shows that gold would most likely exist in pyrite via incorporating into interstitial lattice sites in the absence of As impurity.As a result of incorporated Au,the covalence levels of the S—Fe and S—S bonds are changed,and the tonicity of Au—S bonds and antibonding of Au—Fe bonds are found to form in the pyrite,which would change the natural flotability of pyrite.The Au impurity energy levels are introduced into the energy band and result in the transformation of pyrite semiconductivity type.The calculated band-gap value suggests that the incorporated Au significantly decreases pyrite semiconductivity level,which enhances the formation and the adsorption stability of dixanthogen during pyrite flotation.The DOS results reveal that the stability and depression difficulty level of pyrites increases in the following order:Fe_(32)S_(63)As<Fe_(32)S_(64)<Fe_(32)S_(63)As Au<Fe_(32)S_(64)Au.展开更多
The performance of hydroxamic polyacrylamide(HPAM) in mineral flotation was tested on the samples of calcite, diaspore and pyrite. It is found that HPAM expresses intensive depression on pyrite and can be used as effe...The performance of hydroxamic polyacrylamide(HPAM) in mineral flotation was tested on the samples of calcite, diaspore and pyrite. It is found that HPAM expresses intensive depression on pyrite and can be used as effective depressants for pyrite. The depression mechanism of HPAM to pyrite was investigated by the determination of contact angle, zeta potential, adsorptive capacity for collectors and infrared spectrum. A lower contact angle, more negative zeta potential, less xanthate adsorptive capacity, and the formation of chemical bonding were determined, which reveals that the strong chemical interactions exist between HPAM and pyrite surface. The group electronegativity of HPAM was calculated to explain the differences of interaction between reagent and minerals.展开更多
Acid mine drainage(AMD)has become a widespread environmental issue and its toxicity can cause permanent damage to the ecosystem.However,there are few studies focusing on the formation of AMD under moderately thermophi...Acid mine drainage(AMD)has become a widespread environmental issue and its toxicity can cause permanent damage to the ecosystem.However,there are few studies focusing on the formation of AMD under moderately thermophilic conditions,hence we employed X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and 16S rRNA sequencing to study the dissolution of pyrite and bornite by a moderate thermophilic consortium,and explored the role of free and attached microorganisms in the formation of AMD.The consortium mainly comprised Acidithiobacillus caldus,Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans.The results indicated that total iron in pyrite solution system reached 33.45 g/L on the 12th day,and the copper dissolution rate of bornite dissolution reached 91.8%on the 24th day.SEM results indicated that the surfaces of pyrite and bornite were significantly corroded by microorganisms.XRD and XPS results showed that ore residues contained jarosite,and the dissolving residue of bornite contained elemental sulfur.The dominant bacterial genus in pyrite dissolution was A.caldus,and L.ferriphilum in bornite dissolution.To sum up,microbes significantly accelerated the mineral dissolution process and promoted the formation of AMD.展开更多
Electrokinetic and contact angle measurements were used to discuss the interfacial interaction on bio-leaching of pyrite mineral. Surface energy parameters of pyrite mineral and thiobacillus ferrooxidans were obtained...Electrokinetic and contact angle measurements were used to discuss the interfacial interaction on bio-leaching of pyrite mineral. Surface energy parameters of pyrite mineral and thiobacillus ferrooxidans were obtained by calculating according to formula of Young＇s equation and contact angle measurements. The results show that surface energy of thiobacillus ferrooxidans is much higher than that of pyrite mineral, and the reaction of pyrite mineral with thiobacillus ferrooxidans causes the reduction of the pyrite surface energy. The interfacial interaction energies between pyrite mineral and thiobaciUus ferrooxidans were also obtained based on polar interfacial interaction theory and electrokinetic and contact angle measurements. The thermodynamics approach only considering Lifshitz-van der Waals and Lewis acid-base interaction fails to explain the adhesion behavior of the bacteria, but the extended Derjaguin-Landan-Verwey-Overbeek theory concerning Lifshitz-van der Waals and Lewis acid-base and the electrostatic can exactly predict interfacial interaction.展开更多
Leaching soluble phosphorus from rock phosphate containing pyrites by Acidithiobacillus ferrooxidans (A.f.) is feasible, and the reaction mechanism is as follows. Pyrites are oxidized by A.f. to produce H_2SO_4 and Fe...Leaching soluble phosphorus from rock phosphate containing pyrites by Acidithiobacillus ferrooxidans (A.f.) is feasible, and the reaction mechanism is as follows. Pyrites are oxidized by A.f. to produce H_2SO_4 and FeSO_4; the rock phosphate is decomposed by H_2SO_4, forming soluble phosphorus compounds; and Fe2+ from FeSO_4 is oxidized to Fe^3+, providing energy for the growth of A. f.. In this process, as H_2SO_4 is produced in the reaction, an acidic condition in the culture medium is formed, which benefits the growth of A. f. and aids both continuous oxidation of pyrites and leaching of soluble phosphorus from rock phosphate. The fraction of phosphorous leached can reach the largest in the presence of 1.0 g/L Fe^3+, 200 mg/L Mg^2+ and 400 mg/L NH_4^+. The optimal technological parameters on the fraction of phosphorous leached are as follows: the volume fraction of inocula of A. f., the mass ratio of pyrites to rock phosphate and the pH value are in ranges of 5%-25%, 3:1-5:1 and 1.8-2.2, respectively.展开更多
Sulfide oxidation by microbial activities play an important role in the release of heavy metals. An important source of contamination and formation of AMD is the heavy metals convey to soil, rivulet and groundwater. P...Sulfide oxidation by microbial activities play an important role in the release of heavy metals. An important source of contamination and formation of AMD is the heavy metals convey to soil, rivulet and groundwater. Pyrite is a commonly sulfide minerals in mine wastes, so it is vitally to prove up the microbial oxidation process.展开更多
Micaceous iron oxide （MIO） with a hexagonal flaky shape was prepared by hydrothermal method. The ferric hydroxide used as precursor was obtained by an acidic leaching solution of pyrite cinders reacting with ammonia...Micaceous iron oxide （MIO） with a hexagonal flaky shape was prepared by hydrothermal method. The ferric hydroxide used as precursor was obtained by an acidic leaching solution of pyrite cinders reacting with ammonia solution. The optimal experimental conditions for preparing micaceous iron oxide were investigated by orthogonal experiments. Micaceous iron oxide can be successfully prepared when optimal parameters of total iron concentration of 2.0 mol/L, pH value of 8, n（Fe2＋）/n（Fe3＋） of 0.1, mass of seed crystal of 1 g, reaction temperature of 260 ℃ and reaction time of 30 min are applied. X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and selected area electron diffractometry （SAEM） were adopted to characterize the hydrothermal products prepared under optimal conditions. The results indicate that highly crystallized α-Fe2O3 hexagonal flakes, about 1.0-1.5 μm in diameter and 0.1 μm in thickness, are prepared. Furthermore, the quality of micaceous iron oxide prepared can meet the required characteristics of micaceous iron oxide pigments for paints （ISO 10601--2007）.展开更多
Microorganisms,one of the key factors affecting the bioleaching process,change the components of extracellular polymeric substance(EPS)and community structure to survive in leaching environments.In this work,Fourier t...Microorganisms,one of the key factors affecting the bioleaching process,change the components of extracellular polymeric substance(EPS)and community structure to survive in leaching environments.In this work,Fourier transform infrared(FTIR),X-ray powder diffraction(XRD)and 16S rDNA high-throughput sequence analyses were used to reveal the microbial changes in planktonic and sessile phases during bioleaching.The results showed the occupation of sessile cells decreased from 66.2%to(10±3)%.After bioleaching,the planktonic and sessile cells have similar EPS,but they are different from the original cells.Pyrite dissolution mainly occurs at the early and late stages with the decreasing of particle diameter,by 50%and 40%,respectively.The 16S rDNA gene based sequence analysis results in total of 1117420 Reads across the six samples,presented among 7 phyla,9 classes,17 orders,23 families and 31 genera.Genera Leptospirillum and Sulfobacillus are the main bacteria at the early and middle stages,and Leptospirillum is the main genus at the end of bioleaching.Aquabacterium and Acidovorax are special genera in sessile cells and Weissella is special in planktonic ones.展开更多
Leptospirillum ferriphilum YSK was added to a native consortium of bioleaching bacteria including Acidithiobacillus caldus,A.thiooxidans,A.ferrooxidans,Sulfobacillus thermosulfidooxidans,Acidiphilium spp.,and Ferropla...Leptospirillum ferriphilum YSK was added to a native consortium of bioleaching bacteria including Acidithiobacillus caldus,A.thiooxidans,A.ferrooxidans,Sulfobacillus thermosulfidooxidans,Acidiphilium spp.,and Ferroplasma thermophilum cultured in modified 9K medium containing 0.5%(W/V)pyrite.The bioleaching efficiency markedly increased.Changes in community structure and gene expression were monitored with real-time PCR and functional gene arrays.Dynamic changes that varied in different populations in the consortium occurred after the addition of L.ferriphilum YSK,with growth of A.caldus S1,A.thiooxidans A01,Acidiphillum spp.DX1-1 promoted the growth of Ferroplasma L1,inhibited that of S.thermosulfidooxidans ST,and exerted little effect on that of A.ferrooxidans CMS.Genes encoding ADP heptose,phosphoheptose isomerase,glycosyltransferase,biotin carboxylase,and protoheme ferrolyase from L.ferriphilum,acetyl-CoA carboxylase from Acidiphillum spp.,and doxD from A.caldus were up-regulated in 0-20 h.Genes encoding lipid A disaccharide synthase LpxB,glycosyl transferase,and ADP heptose synthase from A.ferrooxidans were up-regulated in 0-8 h and then down-regulated in 8-20 h.Genes encoding ferredoxin oxidoreductase from Ferroplasma sp.were up-regulated in 0-4 h,down-regulated in 4-16 h,and again up-regulated in 16-20 h.CbbS from A.ferrooxidans was down-regulated in 0-20 h.展开更多
基金Project(52204363)supported by the National Natural Science Foundation of ChinaProject(2024JJ8042)supported by the Hunan Natural Science Foundation,ChinaProject(22C0220)supported by the Education Department of Hunan Province,China。
文摘The lime-Cu^(2+)-xanthate process is commonly used for the flotation separation of sphalerite from pyrite.In this process,lime is added to the pulp to inhibit the floatability of pyrite.However,the excessive use of lime can result in pipeline blockage and inadequate recovery of associated precious metals.Therefore,it is necessary to develop new flotation process that minimizes or eliminates the use of lime.In this paper,a novel Fe^(3+)-Cu^(2+)-butyl xanthate process was developed as an alternative to lime for separating of sphalerite from pyrite.The flotation results indicated that with the artificially-mixed minerals,the flotation recovery of pyrite was lower than 16%and that of sphalerite was higher than 47%at pH 5.0−10.0.The zeta potential measurements revealed that ferric ion preferred to adsorb on pyrite,and copper ion displaced with zinc ion from the lattice at the interface of sphalerite.The wettability analyses indicated that the hydrophobicity of sphalerite surface increased apparently after being treated with Fe^(3+)-Cu^(2+)-BX,while the hydrophobicity of pyrite surface remained nearly unchanged.With XPS analysis,Cu-S bond and hydrophilic ferric hydroxide were detected separately on the surface of sphalerite and pyrite after conditioning with Fe^(3+)-Cu^(2+)-BX,which facilitated the flotation separation of sphalerite from pyrite with butyl xanthate collector.
基金Project(2006AA06Z120) supported by High-Technology Research and Development Program of ChinaProject(1343-74334000028) supported by the Graduate Student Education Innovation Project of Central South University, China
文摘In order to selectively separate chalcopyrite from pyrite,the effect of organic depressant lignosulfonate calcium(LSC) on the flotation separation of chalcopyrite from pyrite was investigated by flotation tests. The depression mechanism was studied by Fourier-transform-infrared(FTIR) analysis. The flotation tests of single mineral show that LSC can depress the flotation of pyrite in a certain pH range,but it has little effect on chalcopyrite flotation. Flotation separation of a mixture of chalcopyrite and pyrite can be completed to obtain a copper concentrate grade up to 24.73% with a recovery of 80.36%. IR analysis shows that LSC and butyl xanthate compete in absorption on pyrite surface,and there exists an LSC characteristic peak on pyrite surface. There is little adsorption of LSC on chalcopyrite.
基金Project(50674102) supported by the National Natural Science Foundation of China
文摘The interaction mechanism of collector DLZ in the flotation process of chalcopyrite and pyrite was investigated through flotation experiments,zeta potential measurements and infrared spectrum analysis.Flotation test results indicate that DLZ is the selective collector of chalcopyrite.Especially,the recovery of chalcopyrite is higher than 90% in neutral and weak alkaline systems,while the recovery of pyrite is less than 10%.When using CaO as pH regulator,at pH=7-11,the floatability of pyrite is depressed and the recovery is less than 5%.Zeta potential analysis shows that the zeta potential of chalcopyrite decreases more obviously than that of pyrite after interaction with DLZ,confirming that collector DLZ shows selectivity to chalcopyrite and pyrite.And FTIR results reveal that the flotation selectivity of collector DLZ is due to chemical absorption onto chalcopyrite surface and only physical absorption onto pyrite surface.
基金Projects(31470230,51320105006,51604308)supported by the National Natural Science Foundation of ChinaProject(2017RS3003)supported by the Youth Talent Foundation of Hunan Province of China+1 种基金Project(2018JJ2486)supported by the Natural Science Foundation of Hunan Province of ChinaProject(2018WK2012)supported by the Key Research and Development Projects in Hunan Province,China。
文摘In this paper,Sulfobacillus thermosulfidooxidans ST was selected for use in bioleaching of pyrite and chalcopyrite.The adsorption experiments revealed that more cells were adsorbed on the surface of pyrite than on the surface of chalcopyrite.The role of extracellular DNA(eDNA)in the bioleaching process was investigated by depletion of eDNA using DNase I.The number of cells attached on the chalcopyrite and pyrite surfaces decreased on a large scale,and the lag phase of cell growth increased,causing the leaching percentages of pyrite and chalcopyrite to decrease by approximately 11.6%and 20.5%,respectively.The formation and distribution of eDNA secreted during bioleaching was assessed by a fluorescent dye-based method and visualized by confocal laser scanning microscopy(CLSM).The content of eDNA increased with bioleaching time.Furthermore,ST showed a stronger capacity to produce eDNA on the surface of pyrite than on the surface of chalcopyrite.These results showed that the removal of eDNA has a more significant effect on the bioleaching of chalcopyrite than on pyrite.
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Project(2008BAE60B00) supported by the National Science & Technology Pillar Program during the Eleventh Five-year Plan Period,China
文摘The flotation tests and XPS analyses on galena,sphalerite and pyrite have been carried out in a collecting-depressing-reactivating system(hereafter referred as the CDR system).In this system,sulfide minerals were first collected and activated by the collector,and then depressed strongly by Ca(OH)2 in the strong alkaline solution,and finally reactivated by H2SO4.The flotation tests of pure minerals show that in this system the flotation behaviors of sphalerite and pyrite present irreversible characteristics along with the change of pulp potential.Furthermore,through the CDR system,considerable differences in the flotabilities between galena and sphalerite/pyrite are also observed.The XPS analysis results for galena,sphalerite and pyrite in a CDR system show that in the strong alkaline solution,some of the collectors,that have been already adsorbed on the mineral surface in the collecting process,are desorbed by Ca(OH)2.The XPS analysis results also show that in H2SO4 reactivating process,the surface hydroxides of galena are desorbed again by H2SO4 and replaced by diethyl dithiocarbamate,but those of sphalerite and pyrite are not desorbed.This flotation system may be applied to the bulk-differential flotation process of sulfur-bearing low-grade lead-zinc ores.
基金Project(51404033)supported by the National Natural Science Foundation of ChinaProject(2010CB630905)supported by the National Basic Research Program of China
文摘Simulated heap bioleaching of low-grade high pyrite-bearing chalcocite ore was conducted at 40 °C with aeration of CO_2 and N_2.Ore samples were collected at day 43,64,85,106 and subjected to microbial community analysis by 16S rRNA gene clone library.Phylogenetic analyses of 16S rDNA fragments revealed that the retrieved sequences are mainly related to genus Acidithiobacillus,Leptospirillum and Sulfobacillus.Aeration of CO_2 and N_2 significantly impacted the microbial community composition.When CO_2 was aerated,the proportion of genus Acidithiobacillus considerably increased,whereas the proportion of genus Leptospirillum and genus Sulfobacillus declined.However,with the aeration of N_2,the proportion of genus Acidithiobacillus and Leptospirillum increased,but genus Sulfobacillus decreased.When there was no aeration,the microbial community was similar to the inocula with the proportion of genus Leptospirillum mounted.These results indicated that the limitation of oxygen could change the bioleaching microbial community and the aeration of CO_2 and N_2 was favourable for the growth of sulfur-oxidizer(At.caldus) and iron-oxidizer(L.ferriphilum) respectively,which could be used for the regulation of microorganisms' role in mineral bioleaching.
文摘The electrode process of pyrite in diethyldithiocarbamate (DDTC) solution pH 11.4 was investigated by using cyclic voltammetry, potentiost atic and chronopotentiometry. Tetraethylthioram disulphide(TETD) was electrodepo sited on pyrite electrode surface as the electrode potential is higher than 0.2 V. The relationship of the current density caused by diffusion and reaction time can be ascertained as i =1/(9.08×10 -5 +4.77×10 -3 t 0.5 ) , and the diffusion coefficient of DDTC on pyrite surface is about 3.72×10 - 6 cm 2/s. At pH 11.4, the thickness of TETD adsorbed on pyr ite surface is about 1.63 molecule layer. The electrochemical dynamics equation of the reduction of TETD on pyrite surface is given as η =0.116-0.064log[1- ( t/τ ) 0.5 ]. The kinetic parameters were determined as follows: the ex change current density ( i 0) is 3.08 μA/cm 2; the transmission coeffi cient( α ) is 0.462.
基金Project(51504155)supported by the National Natural Science Foundation of ChinaProject(BK20140337)supported by the Basic Research Program of Jiangsu Province+2 种基金ChinaProject(SDY2013A13)supported by the Young Teacher Natural Science Fund of Soochow UniversityChina
文摘The role of CaCl2 during the high temperature chloridizing-reduction roasting process was investigated, aiming at acquiring high strength blast furnace burden with high iron grade and low nonferrous metals content. The effects of CaCl2 dosage on pelletizing, preheating and reduction were investigated. The results show that CaCl2 can improve the wet drop strength but reduces the thermostability of pyrite cinder green balls. When the dosage of CaCl2 exceeds 1%, the compressive strength of preheated pellets decreases while the growth of iron oxide particles is improved. Furthermore, the compressive strength of pre-reduced pellets increases but the metallization degree of pre-reduced pellets decreases with CaCl2 additive. The removal tests indicate that Zn can be removed completely without CaCl2 additive, Cu is removed only under the condition with CaCl2 additive and part of Pb must be removed by CaCl2 additive.
基金Project(2008A090300016) supported by the Key Science and Technology Item of Guangdong Province,ChinaProject(ZKJ2010022) supported by the Precious Apparatus Opening Center Foundation of Central South University,China
文摘Well-crystallized hexagonal hematite （α-Fe2O3） platelets were synthesized by hydrothermal process, using a highly concentrated ferric hydroxide as precursor. The precursor was prepared by adding ammonia to the ferric sulfate solution which was obtained by leaching pyrite cinders with sulfuric acid. Structure and morphology of the synthesized products were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope and selected area electron diffraction. The results reveal that the reaction temperature has significant effects on the structure, size and shape of the synthesized hematite particles. Typical hexagonal hematite platelets, about 0.4-0.6 μm in diameter and 0.1 μm in thickness, were prepared at 230 ℃ for 0.5 h. Al^3＋, contained in the sulfuric acid leaching solution as an impurity, plays an extremely important role in the formation of hexagonal hematite. In addition, a possible mechanism about the formation of hexagonal hematite platelets was proposed.
基金Projects(51504109,51504107)supported by the National Natural Science Foundation of China
文摘Various incorporation of Au in pyrite and its effects on the geometrical structure,electronic structure and flotability of pyrite were theoretically investigated and fully discussed by performing density functional theory(DFT).The calculated incorporation energy shows that gold would most likely exist in pyrite via incorporating into interstitial lattice sites in the absence of As impurity.As a result of incorporated Au,the covalence levels of the S—Fe and S—S bonds are changed,and the tonicity of Au—S bonds and antibonding of Au—Fe bonds are found to form in the pyrite,which would change the natural flotability of pyrite.The Au impurity energy levels are introduced into the energy band and result in the transformation of pyrite semiconductivity type.The calculated band-gap value suggests that the incorporated Au significantly decreases pyrite semiconductivity level,which enhances the formation and the adsorption stability of dixanthogen during pyrite flotation.The DOS results reveal that the stability and depression difficulty level of pyrites increases in the following order:Fe_(32)S_(63)As<Fe_(32)S_(64)<Fe_(32)S_(63)As Au<Fe_(32)S_(64)Au.
文摘The performance of hydroxamic polyacrylamide(HPAM) in mineral flotation was tested on the samples of calcite, diaspore and pyrite. It is found that HPAM expresses intensive depression on pyrite and can be used as effective depressants for pyrite. The depression mechanism of HPAM to pyrite was investigated by the determination of contact angle, zeta potential, adsorptive capacity for collectors and infrared spectrum. A lower contact angle, more negative zeta potential, less xanthate adsorptive capacity, and the formation of chemical bonding were determined, which reveals that the strong chemical interactions exist between HPAM and pyrite surface. The group electronegativity of HPAM was calculated to explain the differences of interaction between reagent and minerals.
基金Projects(51934009,52074353)supported by the National Natural Science Foundation of ChinaProject(2019YFC1803600)supported by the National Key Research and Development Program of ChinaProject(2021JJ30855)supported by the Natural Science Foundation of Hunan Province,China。
文摘Acid mine drainage(AMD)has become a widespread environmental issue and its toxicity can cause permanent damage to the ecosystem.However,there are few studies focusing on the formation of AMD under moderately thermophilic conditions,hence we employed X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and 16S rRNA sequencing to study the dissolution of pyrite and bornite by a moderate thermophilic consortium,and explored the role of free and attached microorganisms in the formation of AMD.The consortium mainly comprised Acidithiobacillus caldus,Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans.The results indicated that total iron in pyrite solution system reached 33.45 g/L on the 12th day,and the copper dissolution rate of bornite dissolution reached 91.8%on the 24th day.SEM results indicated that the surfaces of pyrite and bornite were significantly corroded by microorganisms.XRD and XPS results showed that ore residues contained jarosite,and the dissolving residue of bornite contained elemental sulfur.The dominant bacterial genus in pyrite dissolution was A.caldus,and L.ferriphilum in bornite dissolution.To sum up,microbes significantly accelerated the mineral dissolution process and promoted the formation of AMD.
基金Project(2004CB619204) supported by the National Basic Research Program of ChinaProject(2002) supported by the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions, China
文摘Electrokinetic and contact angle measurements were used to discuss the interfacial interaction on bio-leaching of pyrite mineral. Surface energy parameters of pyrite mineral and thiobacillus ferrooxidans were obtained by calculating according to formula of Young＇s equation and contact angle measurements. The results show that surface energy of thiobacillus ferrooxidans is much higher than that of pyrite mineral, and the reaction of pyrite mineral with thiobacillus ferrooxidans causes the reduction of the pyrite surface energy. The interfacial interaction energies between pyrite mineral and thiobaciUus ferrooxidans were also obtained based on polar interfacial interaction theory and electrokinetic and contact angle measurements. The thermodynamics approach only considering Lifshitz-van der Waals and Lewis acid-base interaction fails to explain the adhesion behavior of the bacteria, but the extended Derjaguin-Landan-Verwey-Overbeek theory concerning Lifshitz-van der Waals and Lewis acid-base and the electrostatic can exactly predict interfacial interaction.
基金Project(2004CB619200) supported by the State Basic Research Development Program of ChinaProject(Z200515002) supported by the Key Project Foundation of the Education Department of Hubei Province, China
文摘Leaching soluble phosphorus from rock phosphate containing pyrites by Acidithiobacillus ferrooxidans (A.f.) is feasible, and the reaction mechanism is as follows. Pyrites are oxidized by A.f. to produce H_2SO_4 and FeSO_4; the rock phosphate is decomposed by H_2SO_4, forming soluble phosphorus compounds; and Fe2+ from FeSO_4 is oxidized to Fe^3+, providing energy for the growth of A. f.. In this process, as H_2SO_4 is produced in the reaction, an acidic condition in the culture medium is formed, which benefits the growth of A. f. and aids both continuous oxidation of pyrites and leaching of soluble phosphorus from rock phosphate. The fraction of phosphorous leached can reach the largest in the presence of 1.0 g/L Fe^3+, 200 mg/L Mg^2+ and 400 mg/L NH_4^+. The optimal technological parameters on the fraction of phosphorous leached are as follows: the volume fraction of inocula of A. f., the mass ratio of pyrites to rock phosphate and the pH value are in ranges of 5%-25%, 3:1-5:1 and 1.8-2.2, respectively.
文摘Sulfide oxidation by microbial activities play an important role in the release of heavy metals. An important source of contamination and formation of AMD is the heavy metals convey to soil, rivulet and groundwater. Pyrite is a commonly sulfide minerals in mine wastes, so it is vitally to prove up the microbial oxidation process.
基金Project(2008A090300016) supported by Major Science & Technology Special Program of Guangdong Province,China
文摘Micaceous iron oxide （MIO） with a hexagonal flaky shape was prepared by hydrothermal method. The ferric hydroxide used as precursor was obtained by an acidic leaching solution of pyrite cinders reacting with ammonia solution. The optimal experimental conditions for preparing micaceous iron oxide were investigated by orthogonal experiments. Micaceous iron oxide can be successfully prepared when optimal parameters of total iron concentration of 2.0 mol/L, pH value of 8, n（Fe2＋）/n（Fe3＋） of 0.1, mass of seed crystal of 1 g, reaction temperature of 260 ℃ and reaction time of 30 min are applied. X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and selected area electron diffractometry （SAEM） were adopted to characterize the hydrothermal products prepared under optimal conditions. The results indicate that highly crystallized α-Fe2O3 hexagonal flakes, about 1.0-1.5 μm in diameter and 0.1 μm in thickness, are prepared. Furthermore, the quality of micaceous iron oxide prepared can meet the required characteristics of micaceous iron oxide pigments for paints （ISO 10601--2007）.
基金Project(U1608254)supported by the Special Fund for the National Natural Science Foundation of ChinaProjects(ZJKY2017(B)KFJJ01,ZJKY2017(B)KFJJ02)supported by the Zijin Mining Group Co.,Ltd.,China。
文摘Microorganisms,one of the key factors affecting the bioleaching process,change the components of extracellular polymeric substance(EPS)and community structure to survive in leaching environments.In this work,Fourier transform infrared(FTIR),X-ray powder diffraction(XRD)and 16S rDNA high-throughput sequence analyses were used to reveal the microbial changes in planktonic and sessile phases during bioleaching.The results showed the occupation of sessile cells decreased from 66.2%to(10±3)%.After bioleaching,the planktonic and sessile cells have similar EPS,but they are different from the original cells.Pyrite dissolution mainly occurs at the early and late stages with the decreasing of particle diameter,by 50%and 40%,respectively.The 16S rDNA gene based sequence analysis results in total of 1117420 Reads across the six samples,presented among 7 phyla,9 classes,17 orders,23 families and 31 genera.Genera Leptospirillum and Sulfobacillus are the main bacteria at the early and middle stages,and Leptospirillum is the main genus at the end of bioleaching.Aquabacterium and Acidovorax are special genera in sessile cells and Weissella is special in planktonic ones.
基金Projects(51604308,41771300,41301274)supported by the National Natural Science Foundation of ChinaProject(2017QNCXTD_GTD)supported by the Youth Innovation Team Project of Institute of Subtropical Agriculture,Chinese Academy of Sciences+1 种基金Project(2017YFD0202000)supported by the National Key Research and Development Program of ChinaProject(2020GDASYL-20200402001)supported by the special Project of Science and Technology Development,China。
文摘Leptospirillum ferriphilum YSK was added to a native consortium of bioleaching bacteria including Acidithiobacillus caldus,A.thiooxidans,A.ferrooxidans,Sulfobacillus thermosulfidooxidans,Acidiphilium spp.,and Ferroplasma thermophilum cultured in modified 9K medium containing 0.5%(W/V)pyrite.The bioleaching efficiency markedly increased.Changes in community structure and gene expression were monitored with real-time PCR and functional gene arrays.Dynamic changes that varied in different populations in the consortium occurred after the addition of L.ferriphilum YSK,with growth of A.caldus S1,A.thiooxidans A01,Acidiphillum spp.DX1-1 promoted the growth of Ferroplasma L1,inhibited that of S.thermosulfidooxidans ST,and exerted little effect on that of A.ferrooxidans CMS.Genes encoding ADP heptose,phosphoheptose isomerase,glycosyltransferase,biotin carboxylase,and protoheme ferrolyase from L.ferriphilum,acetyl-CoA carboxylase from Acidiphillum spp.,and doxD from A.caldus were up-regulated in 0-20 h.Genes encoding lipid A disaccharide synthase LpxB,glycosyl transferase,and ADP heptose synthase from A.ferrooxidans were up-regulated in 0-8 h and then down-regulated in 8-20 h.Genes encoding ferredoxin oxidoreductase from Ferroplasma sp.were up-regulated in 0-4 h,down-regulated in 4-16 h,and again up-regulated in 16-20 h.CbbS from A.ferrooxidans was down-regulated in 0-20 h.
