Variation in energy metabolism structure of microbial community during bioleaching chalcopyrites with different iron-sulfur ratios

The energy metabolism structure of microbial community plays an important role in the process of biohydrometallurgy.In this article,an artificial microbial community composed of three strains(Acidithiobacillus ferrooxidans,Leptospirillum ferriphilum and Acidithiobacillus thiooxidans)was used to leach three kinds of chalcopyrites with different iron-sulfur ratios.After 36 d of leaching,the chalcopyrite with iron-sulfur ratio of about 1:1 achieved the highest copper extraction(69.62%).In the early stage,iron oxidizing bacteria predominated,and the expression of rus and rio was 8 times higher than that in the late stage.In the late stage,sulfur oxidizing bacteria predominated,and the expression of tetH and HdrAB was 4 times higher than that in the early stage.Furthermore,the three bioleaching systems above were added with elemental sulfur(3 g/L);the chalcopyrite with iron-sulfur ratio of about 2:1 achieved the highest copper extraction(80.63%).The results suggest that the energy metabolism structure of the microbial community could be changed by changing the iron-sulfur ratio during the leaching process for improving the leaching efficiency of chalcopyrite.

Effect of pyrite content on chalcopyrite flotation under different regrinding conditions

This study aimed to investigate the effect of varying pyrite(Py)content on copper(Cu)in the presence of different regrinding conditions,which were altered using different types of grinding media:iron,ceramic balls,and their mixture,followed by flotation in the cleaner stage.The flotation performance of rough Cu concentrate can be improved by changing the regrinding conditions based on the Py content.Scanning electron microscopy,X-ray spectrometry,ethylenediaminetetraacetic acid disodium salt extraction,and X-ray photoelectron spectroscopy studies illustrated that when the Py content was high,the use of iron media in regrinding promoted the generation of hydrophilic Fe OOH on the surface of Py and improved the Cu grade.The ceramic medium with a low Py content prevented excessive Fe OOH from covering the surface of chalcopyrite(Cpy).Electrochemical studies further showed that the galvanic corrosion current of Cpy-Py increased with the addition of Py and became stronger with the participation of iron media.

A novel molybdenite depressant for efficient selective flotation separation of chalcopyrite and molybdenite

A novel small molecule depressant(M-DEP)was used to separate chalcopyrite and molybdenite via flotation.The results showed that M-DEP had an excellent selective depression on molybdenite,while had little effect on the flotation of chalcopyrite.The adsorption capacity of M-DEP on the surface of molybdenite was greater than that on chalcopyrite surface.The adsorption of M-DEP reduced the floatability of molybdenite and had less effect on the floatability of chalcopyrite,which was due to its different adsorption modes on the surface of the two minerals.Furthermore,the interaction between chalcopyrite and M-DEP was mainly chemical interaction,and almost all of the adsorbed M-DEP molecules were removed and replaced by sodium butyl xanthate(SBX).By contrast,hydrophobic interaction was the main way in which M-DEP was adsorbed on the molybdenite surface with little chemical interaction,which was less interfered by SBX addition.Therefore,M-DEP had a super selective depression on molybdenite.The study provided a novel depressant and approach for the deep separation of chalcopyrite and molybdenite via flotation.

Ferric ion-triggered surface oxidation of galena for efficient chalcopyrite-galena separation

The efficient separation of chalcopyrite(CuFeS2)and galena(PbS)is essential for optimal resource utilization.However,find-ing a selective depressant that is environmentally friendly and cost effective remains a challenge.Through various techniques,such as mi-croflotation tests,Fourier transform infrared spectroscopy,scanning electron microscopy(SEM)observation,X-ray photoelectron spec-troscopy(XPS),and Raman spectroscopy measurements,this study explored the use of ferric ions(Fe^(3+))as a selective depressant for ga-lena.The results of flotation tests revealed the impressive selective inhibition capabilities of Fe^(3+)when used alone.Surface analysis showed that Fe^(3+)significantly reduced the adsorption of isopropyl ethyl thionocarbamate(IPETC)on the galena surface while having a minimal impact on chalcopyrite.Further analysis using SEM,XPS,and Raman spectra revealed that Fe^(3+)can oxidize lead sulfide to form compact lead sulfate nanoparticles on the galena surface,effectively depressing IPETC adsorption and increasing surface hydrophilicity.These findings provide a promising solution for the efficient and environmentally responsible separation of chalcopyrite and galena.

Hydrometallurgical processing of chalcopyrite:A review of leaching techniques

Copper,an essential metal for the energy transition,is primarily obtained from chalcopyrite through hydrometallurgical and pyrometallurgical methods.The risks and harmful impacts of these processes pose significant concerns for environmental and human safety,highlighting the need for more efficient and eco-friendly hydrometallurgical methods.This review article emphasizes current pro-cesses such as oxidative leaching,bioleaching,and pressure leaching that have demonstrated efficiency in overcoming the complicated chalcopyrite network.Oxidative leaching operates under benign conditions within the leaching media;nevertheless,the introduction of oxidizing agents provides benefits and advantages.Bioleaching,a non-aggressive method,has shown a gradual increase in copper extrac-tion efficiency and has been explored using both primary and secondary sources.Pressure leaching,known for its effectiveness and se-lectivity in copper extraction,is becoming commercially more viable with increased research investments.This research also provides im-portant data for advancing future research in the field.

Flotation separation of chalcopyrite from galena by sodium humate and ammonium persulfate

The flotabilities of chalcopyrite and galena with sodium humate（HA） and ammonium persulfate（APS） as the depressant were studied by flotation test, adsorption measurement and infrared spectroscopic analysis. Single mineral flotation test shows that the slurry oxidation environment and the proper oxidation of galena surface are prerequisites for the depression of galena by sodium humate. The closed-circuit flotation test of copper/lead bulk concentrate shows that the grade and recovery of Cu reach 30.47% and 89.16% respectively and those of Pb reach 2.06% and1.58% respectively in copper concentrate, and the grade and recovery of Pb reach 50.34% and 98.42% and those of Cu reach 1.45% and 10.84% respectively in lead concentrate with HA and APS. The selective depression effect of HA and APS is more obvious than that of potassium dichromate. The results of FTIR analysis and adsorption measurements indicate that the adsorption of sodium humate on the fresh surface of galena is negligible, while after oxidation, sodium humate can be chemically adsorbed on the surface of galena. According to the theory of solubility product, the sodium humate can display the oxidation product PbSO_4, after then, adsorb on the surface of lead chemically to produce inhibitory effect. Thus, it can be seen that the combination of HA and APS is an efficient non-toxic reagent to achieve cleaning separation copper/lead bulk concentrate by flotation. The combination of HA and APS is an efficient non-toxic reagent to achieve cleaning for copper/lead bulk concentrate by flotation.

Selective depression effect in flotation separation of copper-molybdenum sulfides using 2,3-disulfanylbutanedioic acid

2,3-disulfanylbutanedioic acid（DMSA） was found to be a selective depressant in the flotation separation of coppermolybdenum sulfides.The flotation results suggest that a low dosage of DMSA has a strong depression effect on chalcopyrite in the p H range between 4 and 12.At p H 6,the recoveries of molybdenum are up to 85%,75%,and 80% while those of chalcopyrite are 15%,5%,and 20% respectively when flotation tests are carried out with single minerals,mixed minerals and molybdenum-bearing copper concentrates.Adsorption isotherms measurement indicates that DMSA adsorbs more strongly on chalcopyrite than on molybdenite.The frontier orbital calculation reveals that the two S atoms of DMSA molecule are active centers for the adsorption of the DMSA molecule on chalcopyrite surface.Fermi level calculation shows that chalcopyrite can obtain electrons from the DMSA molecule while molybdenite cannot.

Relationship and effect of redox potential,jarosites and extracellular polymeric substances in bioleaching chalcopyrite by acidithiobacillus ferrooxidans

The changes of pH,redox potential,concentrations of soluble iron ions and Cu^2＋ with the time of bioleaching chalcopyrite concentrates by acidithiobacillus ferrooxidans were investigated under the different conditions of initial total-iron amount as well as mole ratio of Fe（III） to Fe（II） in the solutions containing synthetic extracellular polymeric substances （EPS）.When the solution potential is lower than 650 mV （vs SHE）,the inhibition of jarosites to bioleaching chalcopyrite is not vital as EPS produced by bacteria can retard the contamination through flocculating jarosites even if concentration of Fe（III） ions is up to 20 g/L but increases with increasing the concentration of Fe（III） ions;jarosites formed by bio-oxidized Fe3＋ ions are more easy to adhere to outside surface of EPS space on chalcopyrite;the EPS layer with jarosites acts as a weak diffusion barrier to further rapidly create a high redox potential of more than 650 mV by bio-oxidizing Fe^2＋ ions inside and outside EPS space into Fe^3＋ ions,resulting in a rapid deterioration of ion diffusion performance of the EPS layer to inhibit bioleaching chalcopyrite severely and irreversibly.

Interaction mechanism of Cu^(2+),Fe^(3+) ions and extracellular polymeric substances during bioleaching chalcopyrite by Acidithiobacillus ferrooxidans ATCC2370

The extracellular polymeric substances（EPS） of Acidithiobacillus ferrooxidans ATCC 23270,and iron and copper enclosed in EPS were extracted by ultrasonication and centrifugation methods to determine the interaction mechanism of Cu2＋,Fe3＋ and EPS during bioleaching chalcopyrite.Generally,Cu2＋ ions can stimulate bacteria to produce more EPS than Fe3＋ ions.The mass ratio of Fe3＋/Cu2＋ enclosed in EPS decreased gradually from about 4：1 to about 2：1 when the concentration of Cu2＋ ions increased from 0.01 to 0.04 mol/L.The amount of iron and copper bound together by EPS in ferrous-free 9K medium containing 1% chalcopyrite was about 2 times of that in 9K medium containing 0.04 mol/L Cu2＋ ions.It was inferred that the EPS with jarosites on the surface of chalcopyrite gradually acted as a weak diffusion barrier for Cu2＋,Fe3＋ ions transference during bioleaching chalcopyrite.

Adsorption and activation of copper ions on chalcopyrite surfaces:A new viewpoint of self-activation

The adsorption behaviors of copper ions on chalcopyrite surfaces were investigated based on zeta potential measurements, X-ray photoelectron spectroscopy, copper ion adsorption experiments, first-principles calculations, and Hallimond tube cell flotation experiments. The results show that copper ions activate the chalcopyrite as a result of the interactions between copper ions and sulfur on the chalcopyrite surface. This adsorption increases the flotation rate under certain conditions, and this is beneficial for the flotation of chalcopyrite. The copper ions in the flotation pulp are mainly derived from surface oxidation dissolution and the release of fluid inclusions, and these effects enable chalcopyrite to be activated.

Effect of EPS on adhesion of Acidithiobacillus ferrooxidans on chalcopyrite and pyrite mineral surfaces

Extracellular polymeric substances （EPS） were extracted from Acidithiobacillus ferrooxidans through sonication method associated with centrifugation, which was evaluated tentatively with 2-keto-3-deoxyoctonic acid （KDO） as the indicator of EPS by spectrophotometry. Then the effect of EPS of A. ferrooxidans on the adhesion on chalcopyrite and pyrite surfaces was studied through a series of comparative experiments. The untreated cells and EPS-free cells of A. ferrooxidans were mixed with EPS suspension, Fe^2＋ or Fe^3＋, respectively. The planktonic cells were monitored in 2 h during bioleaching. The results indicate that the presence of EPS on the cell is an important factor for the adhesion to chalcopyrite and pyrite. A decrease of attachment of A. ferrooxidans to minerals was produced by the deficiency of EPS, which can recover mostly when the EPS was re-added into the EPS-free cells. The restoring extent is more obvious in pyrite than in chalcopyrite. The extent of cell adhesion to chalcopyrite increased when EPS and Fe^3＋ added, and decreased when Fe^2＋ added, which imply the electrostatic interaction plays a main role in initial adhesion between bacteria and minerals and it is a driving force for bacteria to produce EPS probably as a result of regaining their attachment ability to copper sulphides.

Control method of chalcopyrite passivation in bioleaching

Passivation is a common phenomenon on the surface of chalcopyrite in the process of bioleaching. The ordinary leaching and strengthening leaching by adding glass beads were carried out. The results show that the passivation of chalcopyrite was greatly weakened in strengthening leaching due to the change of leaching conditions. The copper leaching efficiency was increased from 50% to 89.8% through adding beads. The SEM and X-ray diffraction （XRD） analyses illustrate that there are few jarosite precipitates and weak passivation on the surface of chalcopyrite in strengthening leaching. In contrast, there are thick and compact jarosite precipitate and obvious passivation in ordinary leaching, which hinders further dissolution of chalcopyrite.

Selective depression of galena and chalcopyrite by O,O-bis(2,3-dihydroxypropyl) dithiophosphate

A novel synthesized reagent, O,O-bis（2,3-dihydroxypropyl） dithiophosphate （DHDTP）, was investigated as depressant on the depression of chalcopyrite and galena, when ammonium dibutyl dithiophosphate （DDTP） was used as the collector in flotation tests. Zeta potential and adsorption measurement were performed to study the interaction between depressant and minerals. The flotation tests of two minerals show that DHDTP has slight depression on chalcopyrite in the whole pH range and strong depression on galena in the pH range of 6-10. When DHDTP dosage is increased, the recovery of galena decreases rapidly, while that of the chalcopyrite decreases slightly. The satisfied separation results of artificially mixed samples are that the copper grade and recovery rates of concentrate are 24.08% and 81%, respectively, when the pH is 6 with 278 mg/L DHDTP. Zeta potential and adsorption measurements show that DHDTP has more strongly adsorotion capacity to galena than chalcoovrite.

Depression effect of pseudo glycolythiourea acid in flotation separation of copper-molybdenum

Pseudo glycolythiourea acid（PGA） was synthesized and used as depressant for flotation separation of Cu and Mo.The results indicate that a low amount of PGA has strong depression effect on chalcopyrite.Mo grade of 26.17% and recovery of 89.83% were achieved with rougher and scavenger one time and cleaners twice,while the recovery of Mo was deceased by 2% when Na2S was used as depressant.Measurement on adsorption of PGA on the mineral surface indicates that PGA and xanthate were adsorbed on mineral surface by competition,and PGA was adsorbed on chalcopyrite surface much stronger than on molybdenite surface.FTIR results indicate a chemical absorption process for PGA on chalcopyrite surface and a physical adsorption process on molybdenite surface.The frontier orbital calculation shows that the S atom is an active center,and the depression of PGA can be explained with the Fermi level of energy based on the electrochemical mechanism.

Bioleaching of Pb-Zn-Sn chalcopyrite concentrate in tank bioreactor and microbial community succession analysis

The variation of microbial community structure was investigated for the tank bioleaching process of Pb-Zn-Sn chalcopyrite concentrate in the presence of mixed moderately thermophilic bacteria. The parameters, such as pH value, solution potential and concentrations of metal ions, were determined by the method of polymerase chain reaction-restriction fragment length polymorphism （PCR-RFLP） to analyze the succession of microbial community. The results showed that a final copper extraction rate of 85.6% could be obtained after tank bioleaching for 30 d. The Acidithiobacillus caldus was the dominant population with abundance of about 73.80%in the initial stage, then Sulfobacillus thermosulfidooxidans dominated from the 18th day to the end of bioleaching, while the abundance of Leptospirillum ferriphilum changed slightly. A higher solution potential within a certain range and appropriate concentration of ferric ions were essential for this tank bioleaching of chalcopyrite.

Comparison of electrochemical dissolution of chalcopyrite and bornite in acid culture medium

The electrochemical dissolution process of chalcopyrite and bornite in acid bacteria culture medium was investigated by electrochemical measurements and X-ray photoelectron spectroscopy（XPS） analysis. Bornite was much easier to be oxidized rather than to be reduced, and chalcopyrite was difficult to be both oxidized and reduced. The relatively higher copper extraction of bornite dissolution can be attributed to its higher oxidation rate. Covellite（CuS） was detected as the intermediate species during the dissolution processes of both bornite and chalcopyrite. Bornite dissolution was preferred to be a direct oxidation pathway, in which bornite was directly oxidized to covellite（CuS） and cupric ions, and the formed covellite（CuS） may inhibit the further dissolution. Chalcopyrite dissolution was preferred to be a continuous reduction-oxidation pathway, in which chalcopyrite was initially reduced to bornite, then oxidized to covellite（CuS）, and the initial reduction reaction was the rate-limiting step.

Effect of initial pH on chalcopyrite oxidation dissolution in the presence of extreme thermophile Acidianus manzaensis

The influence of initial pH on the chalcopyrite oxidation dissolution at 65 ℃ was investigated by bioleaching and cyclic voltammetiy experiments,and the oxidation products were investigated by XRD and Raman spectroscopy.Bioleaching results show that chalcopyrite dissolution rate increases with the decrease of the initial pH in chemical leaching,while the influence of initial pH on bioleaching is on the contrary.The presence of Acidianus manzaensis does not promote chalcopyrite dissolution under initial pH1.0,which mainly results from serious inhibition of high acidity to the growth of Acidianus manzaensis.Electrochemical experiments results show that anodic oxidation currents of electrolyte with or without Acidianus manzaensis both increase with the increase of initial pH,and covellite and sulfur are detected on the electrode surface.The results confirm that chalcopyrite dissolution in chemical leaching is under the combined action of oxidation and non-oxidation of proton,with conversion of chalcopyrite to covellite and elemental sulfur.

Effect of potential on characteristics of surface film on natural chalcopyrite

Electrochemical behavior of natural chalcopyrite in electrolyte solution containing 5×10？4 mol/L ethyl xanthate, and the effect of potential on the composition and characteristics of surface film were studied by cyclic voltammetry （CV）, scanning electron microscopy （SEM） and electrochemical impedance spectroscopy （EIS）. The adsorption of xanthate （X？） occurred on the mineral surface at open-circuit potential （OCP）. In the potential range from -0.11 to 0.2 V, the electrochemical reaction related to the formation of the hydrophobic film of dixanthogen （X2） occurred on natural chalcopyrite surface. This surface film had high coverage and large thickness at the potential of 0 V, but it had low coverage and small thickness at the potentials of 0.1 V and 0.2 V. Electrochemical activation started to occur when the potential was higher than 0.2 V, and the film of X2 transformed to plenty of Cu（Ⅱ） and Fe（Ⅲ） oxygen-containing species which had the porous and loose characteristics.

Surface species of chalcopyrite during bioleaching by moderately thermophilic bacteria

X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） analyses were carried out to investigate the surface species and interfacial reactions during bioleaching of chalcopyrite by different strains of moderately thermophilic bacteria （45 °C）. Results show that monosulfide （CuS）, disulfide （S22？）, polysulfide （Sn2？）, elemental sulfur （S0） and sulfate （SO42？） are the main intermediate species on the surface of chalcopyrite during bioleaching byA. caldus,S. thermosulfidooxidans andL. ferriphilum. The low kinetics of dissolution of chalcopyrite inA. caldus can be mainly attributed to the incomplete dissolution of chalcopyrite and the passivation layer of polysulfide. Polysulfide and jarosite should be mainly responsible for the passivation of chalcopyrite in bioleaching byL. ferriphilumorS. thermosulfidooxidans. However, elemental sulfur should not be the main composition of passivation layer of chalcopyrite during bioleaching.

Theory analysis and vestigial information of surface relaxation of natural chalcopyrite mineral crystal

X-ray diffraction was used to measure the unit cell parameters of chalcopyrite crystal.The results showed that the chalcopyrite crystal is perfect,and the arrangement of its atoms is regular.A qualitative analysis of molecular mechanics showed that surface relaxation causes the chalcopyrite surface to be sulfur enriched.Atomic force microscope（AFM） was used to obtain both a microscopic three-dimensional topological map of chalcopyrite surface and a two-dimensional topological map of its electron cloud.The AFM results revealed that the horizontal and longitudinal arrangements of atoms on the chalcopyrite surface change dramatically compared with those in the interior of the crystal.Longitudinal shifts occur among the copper,iron and sulfur atoms relative to their original positions,namely,surface relaxation occurs,causing sulfur atoms to appear on the outermost surface.Horizontally,AFM spectrum showed that the interatomic distance is irregular and that a reconstruction occurs on the surface.One result of this reconstruction is that two or more atoms can be positioned sufficiently close so as to form atomic aggregates.The lattice properties of these models were calculated based on DFT theory and compared with the experimental results and those of previous theoretical works.On analyzing the results,the atomic arrangement on the（001） surface of chalcopyrite is observed to become irregular,S atoms move outward along the Z-axis,and the lengths of Cu—S and Fe—S bonds are enlarged after geometry optimization because of the surface relaxation and reconstruction.The sulfur-rich surface and irregular atomic aggregates caused by the surface relaxation and reconstruction greatly influence the bulk flotation properties of chalcopyrite.