Dissolution Of Chalcopyrite Research Articles

Chemical Dissolution of Chalcopyrite Concentrate in Choline Chloride Ethylene Glycol Deep Eutectic Solvent

Currently, the high demand for copper is in direct contrast with the decrease in the mineral grade and, more significantly, the concerns regarding the environmental impact that arise as a result of processing such low-grade materials. Consequently, new mineral processing concepts are needed. This work explores the chemical dissolution of chalcopyrite concentrate at ambient pressure and moderate temperatures in a deep eutectic solvent. Copper and iron are dissolved without changing their oxidation state, without solvent pH change, and stabilized as a chloride complex with no evidence of passivation. Chemical equilibria of the metallic chloride complexes limit the dissolution, and the step that is rate-controlling of the kinetics is the interdiffusion of species in the solvent. The chemical mechanism may involve initial chloride adsorption at positive sites of the solid surface, pointing out the importance of surfaces states on chalcopyrite particles. A model based on a shrinking particle coupled with pseudo-second-order increase in the liquid concentration of copper describes the dissolution kinetics and demonstrates the importance of the liquid to solid ratio. Iron and copper can be recovered separately from the solvent, which highlights that this concept is an interesting alternative to both redox-hydrometallurgy and pyrometallurgy to obtain copper by the processing of chalcopyrite concentrate.

The Role of the Iodide/Iodine Couple as a Redox Mediator in the Dissolution of Chalcopyrite in Sulfate Media. An Electrochemical Study

The Role of the Iodide/Iodine Couple as a Redox Mediator in the Dissolution of Chalcopyrite in Sulfate Media. An Electrochemical Study

Combined effect and mechanism of visible light and Ag+ on chalcopyrite bioleaching

• Visible light and Ag + have synergistic catalytic effect on chalcopyrite bioleaching. • Ag + introduced Ag 2 S and Ag 0 on the surface of chalcopyrite. • Light illumination promoted the formation of Ag 2 S and Ag 0 on chalcopyrite surface. • The formation of covellite-like species hindered the dissolution of chalcopyrite. • Ag + and visible light reduced the resistance of the passivation layer. The effect and mechanism of visible light and Ag + on chalcopyrite bioleaching were investigated in the presence of Acidithiobacillus ferrooxidans . The results of bioleaching tests revealed that the copper extraction was improved significantly when visible light and Ag + were simultaneously present. By analyzing bioleaching parameters, scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy results: the accumulation of jarosite and the formation of covellite-like species led to the slow dissolution rate of chalcopyrite at the end period of bioleaching. The introduction of Ag + resulted in the formation of Ag 2 S and Ag 0 on the surface of chalcopyrite. And light illumination promoted the accumulation of Ag 2 S and Ag 0 on chalcopyrite surface, thus reducing the resistance of the passivation layer. Further, light illumination increased the rate of charge transfer and promoted the dissolution of chalcopyrite.

Bioleaching of copper from chalcopyrite ore at higher NaCl concentrations

The formation of hydrolyzed ferric iron (Fe (III)) as jarosite could limit the bioleaching of copper and significantly lower the dissolution rate of low-grade chalcopyrite ore. Thus, to improve the rate through overcoming the hindered dissolution of chalcopyrite, this study investigated the influence of chloride addition into leaching lixiviant. As a microbial source, mixed mesophiles, moderately thermophilic, and thermophilic microorganisms were adapted to about 120 mM NaCl solution. After optimization of the ore bioleaching in 64 controlled mini-columns, the scaled tests in 2-m tall columns were conducted to study the overall leaching procedure and precipitation of the jarosite. Under normal aeration conditions (0.05 Nm3/m2/h) with hybrid irrigation (120 mM NaCl in H2SO4 solution at pH = 1.5), copper recovery reached 80% after 120 days while it was approximately 50% with limited one (0.003 Nm3/m2/h). The limited aeration column had a moderate oxidation–reduction potential (ORP) with values < 450 mV. This significant improvement in dissolution is explained by the reduced precipitation of passivating layer (mainly jarosite). These conclusions were also confirmed by the estimation of pyrite and natrojarosite with a modified ASTM D-2492 (MASTM D-2492). Moreover, to identify the microbial communities in the columns, DNA extraction and 16Sr RNA gene PCR amplification and sequencing were done.

Effect of microwave pretreatment on chalcopyrite dissolution in acid solution

Microwave-roasting as an efficient method for extracting copper form chalcopyrite has attracted increasing attention. In this work, the microwave roasted chalcopyrite was pressure leached in 1.0 mol/L sulfuric acid solution at the temperature range of 110–150 °C, and the reasons why microwave-roasting improved the leaching kinetics were further studied by the electrochemical characterizations. Results show that microwave-roasting had a positive effect on better mineral leachability. Under the optimal conditions, the final copper extraction was 90.1% and the iron extraction was 87.5%. The leaching process of the microwave roasted chalcopyrite was controlled by chemical reaction, and the calculated activation energy was 41.7 kJ/mol. The electrochemical study results indicated that microwave-roasting had a significant effect on both the anodic dissolution kinetics and the cathodic reactions kinetics, and the charge transfer resistance of chalcopyrite oxidation and the resistance of the passive film were both lower than that of the un-roasted sample. X-ray diffraction (XRD), and scanning electron microscope (SEM) results suggested that microwave-roasting effectively activate chalcopyrite through modifying the surface structure. Besides the enlargement of the effective reaction surface, the differential scanning calorimetry-thermogravimetric analysis (DSC-TGA) results revealed that the increasing of active sites and/or the internal stress can increase the strain energy and instability of chalcopyrite, which plays an important role in improving chalcopyrite leaching kinetics. The main product of pressure leaching was elemental sulfur that mixed with the copper-rich sulfide, causing the passivation of chalcopyrite.

Dissolution of Chalcopyrite in Presence of Chelating Agent and Hydrogen Peroxide

Dissolution of Chalcopyrite in Presence of Chelating Agent and Hydrogen Peroxide

Rapid Atmospheric Leaching of Chalcopyrite Using a Novel Reagent of Trichloroisocyanuric Acid

With the decrease in high-grade chalcopyrite resources, the copper extraction from low-grade chalcopyrite has attracted more and more attention. However, the kinetic rates of chalcopyrite leaching with traditional oxidants are usually very slow due to the formation of the passivation layer. In this study, a novel reagent of chlorinated oxidant, trichloroisocyanuric acid (TCCA), was used to leach chalcopyrite for the first time. The experimental results showed that when the initial oxidant concentration for TCCA was 0.054 mol·L−1, the leaching temperature was kept at 55 °C, and the pH of the pulp was controlled at 1, the oxidation efficiency of Cu can reach above 90% in less than 30 min. Various analyses of chalcopyrite mineral ore and its oxidized residues, such as chemical composition analysis, X-ray diffraction analysis, scanning electron microscopy analysis and X-ray photoelectron spectroscopy, were conducted, respectively. No obvious passivation layer was found on the chalcopyrite surface, though the sulfur product can also be generated during the leaching. Reaction kinetic analysis results showed that the different influence of surface reaction and diffusion process on the dissolution of chalcopyrite is little due to the fast leaching speed. After calculation, the activation energy of the whole leaching reaction is 9.06 kJ·mol−1, much lower than that in other reports. The mechanism was also proposed that TCCA was hydrolyzed in the solution to form hypochlorous acid, which is the strong oxidant, and cyanuric acid, which prevents the formation of a passivation layer. The processing in this study is expected to be applied as a novel method for atmospheric leaching of chalcopyrite.

Extraction of copper from chalcopyrite with potassium dichromate in 1-ethyl-3-methylimidazolium hydrogen sulfate ionic liquid aqueous solution

Developing new and sustainable leaching system with limited release of pollutant and low acid and energy consumption is a challenge for copper extraction from chalcopyrite. In this work, a hydrometallurgical process for chalcopyrite dissolution in 1-ethyl-3-methyl-imidazolium hydrogen sulfate ([EMIm]HSO4) media with potassium dichromate (K2Cr2O7) was developed, and the leaching behavior of chalcopyrite with various parameters, such as kinds of ionic liquids (ILs), concentrations of [EMIm]HSO4 and K2Cr2O7, stirring speed, leaching temperature, and particle size were discussed in detail. The result show that the most effective ILs medium for chalcopyrite dissolution was varied with the specific oxidant. The leaching rate of chalcopyrite was significantly enhanced by increasing temperature, concentrations of K2Cr2O7 and [EMIm]HSO4, and decreasing particle size, while it has little to do with the increasing of stirring speed. The maximum copper extraction yield of 90.2% was reached within 90 min under the following optimized conditions: 10 g/L of solid/liquid ratio, 10 vol% of [EMIm]HSO4 concentration, 0.1 M of initial K2Cr2O7 concentration, stirring speed of 200 rpm, the temperature of 70 °C and particle size of −45 µm. The leaching process of chalcopyrite in [EMIm]HSO4-K2Cr2O7 aqueous solution follows an empirical kinetic model 1-2/3x-(1-x)2/3=kdt with the apparent activation energy of 36.26 kJ/mol, which was limited by the diffusion through a protect layer of elemental sulfur and pyrite.

Iron-Speciation Control of Chalcopyrite Dissolution from a Carbonatite Derived Concentrate with Acidic Ferric Sulphate Media

The mechanisms involved in the dissolution of chalcopyrite from a carbonatite concentrate in a ferric sulphate solution at pH 1.0, 1.5 and 1.8, and temperatures 25 °C and 50 °C were investigated. Contrary to expectations and thermodynamic predictions according to which low pH would favour high Cu dissolution, the opposite was observed. The dissolution was also highly correlated to the temperature. CuFeS2 phase dissolution produced intermediate Cu rich phases: CuS, Cu2S and Cu5FeS4, which appeared to envelop CuFeS2. Thermodynamic prediction revealed CuS to be refractory and could hinder dissolution. CuFeS2 phase solid-state dissolution process was further discussed. Free Fe3+ and its complexes (Fe(HSO4)2+, Fe(SO4)2– and FeSO4+ were responsible for Cu dissolution, which increased with increasing pH and temperature. The dissolution improved at pH 1.8 rather than 1.0 due to the increase of (Fe(HSO4)2+, Fe(SO4)2– and FeSO4+, which were also the predominating species at a higher temperature. The fast and linear first dissolution stage was attributed to the combined effect of Fe3+ and its complex (Fe(HSO4)2+, while Fe(SO4)2– was the main species for the second Cu dissolution stage characterised by a slow rate.

Regulation of lead oxide on Cyaniding Behavior of chalcopyrite

During the cyanidation of gold‑copper ores and concentrates, the chalcopyrite significantly increases cyanide consumption. The effects of PbO on the chalcopyrite dissolution mechanisms were studied by SEM and XPS analyses during cyanation. A small amount of PbO could promote the dissolution of chalcopyrite, while more PbO would inhibit dissolution. When 0.5 g/L PbO was added, the main lead compound on the surface of chalcopyrite was PbS, which could enhance the electron transfer between cyanide and chalcopyrite, thus facilitating the dissolution of chalcopyrite. The amount of PbS precipitates increased in the leaching system when the amount of PbO was more than 0.5 g/L. This reduced prominently the free sulfide ions concentration in the solution. PbS would be oxidized to form thiocyanate and lead (II) ions when the concentration of sulfur ions decreased continuously in the solution. These lead (II) ions would react with OH– to form Pb(OH)2 precipitates, which attach to the surfaces of chalcopyrite and inhibit its dissolution in cyanide solutions. The developed method can not only improve the leaching rate of gold but also reduce the consumption of reagents.

The use of pyrite to control redox potential to enhance chalcopyrite bioleaching in the presence of Leptospirillum ferriphilum

Redox potential (ORP) was proved to be a key factor in promoting chalcopyrite (CuFeS2) bioleaching. Though there are some methods for maintaining ORP reported previously, little attention has been given to control it via pyrite. In this work, chalcopyrite bioleaching was investigated in the presence of Leptospirillum ferriphilum (L. ferriphilum) with various amounts of pyrite addition. Bioleaching results showed that the addition of pyrite extremely enhanced the dissolution of chalcopyrite, especially when the mass ratio of pyrite and chalcopyrite was 3:1. In this case, ORP was well maintained at an appropriate range (350–370 mV vs. Ag/AgCl) for 25 days. The results of electrochemical tests indicated that the addition of pyrite did not change the electrochemical dissolution mechanism of chalcopyrite. Thus, the effect of pyrite was mainly a redox potential controlling process, and the reduction of chalcopyrite to secondary copper-iron species like chalcocite (Cu2S) was promoted in the optimum range. Eventually, a high copper extraction (70%) was obtained as a result of the rapid dissolution of formed chalcocite. Based on all the obtained results, a model for illustrating the ORP control of pyrite during chalcopyrite bioleaching in the presence of L. ferriphilum was proposed.

The initial stages of the dissolution of chalcopyrite in chloride solutions: Validity of mixed potential model and comparison with sulfate solutions

A relatively simple electrochemical method has been used to obtain accurate data on the rates of oxidative dissolution of chalcopyrite from well defined surface areas under ambient conditions using iron(III) or copper(II) (in chloride solutions) as the oxidants. The initial rates are approximately constant for extended (6 h) periods in chloride solutions but decrease with time in sulfate solutions.The rates of dissolution are not strongly dependent on the nature of the solution except in solutions of high chloride concentration for which the rates are higher. The rate is also slightly higher with copper(II) or with iron(III) + copper(II) as the oxidant. A limited study has shown the importance of temperature with an activation energy of 57 kJ mol−1 for dissolution in chloride solution.The chalcopyrite mixed potentials measured during dissolution vary over a limited range (less than 200 mV) depending on the conditions. Potentiostatic measurements in solutions without oxidants have shown that the rates calculated from the current densities at the mixed potentials agree quantitatively with those obtained from the chemical dissolution measurements. This correspondence confirms the validity of the mixed potential model for oxidative dissolution. Comparisons have been made with previously published data largely at elevated temperatures.

Chalcopyrite leaching in ammonium chloride solutions under ambient conditions: Insight into the dissolution mechanism by XANES, Raman spectroscopy and electrochemical studies

Ammoniacal leaching solutions have been considered as an effective lixiviant for the oxidative dissolution of chalcopyrite. However, compared with the extensive studies of acidic chalcopyrite dissolution, the dissolution mechanism of chalcopyrite in ammoniacal solutions needs further understanding. In this study, the oxidative dissolution of chalcopyrite in ammonium chloride solutions under room temperature and pH 8.5 was studied by X-ray absorption near-edge spectroscopy (XANES), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). Both batch leaching experiments and electrochemical studies showed that Cu(II) ions were more efficient than dissolved oxygen for chalcopyrite oxidation in ammonium chloride solutions. Leaching kinetics analysis showed that without the initial addition of Cu(II), chalcopyrite dissolution rate was controlled by two different stoichiometric chemical reactions: the initial and slow leaching stage controlled by dissolved oxygen; then predominated by Cu(II) rather than dissolved oxygen with a fast leaching rate when copper concentration exceeded a certain level (>0.12 g/L). Thiosulfate (S2O32−) rather than sulfate (SO42−) was confirmed as the primary soluble sulfur species produced during chalcopyrite dissolution. Decomposition of S2O32− in the presence of both O2 and Cu(II) resulted in the final stable product SO42− accompanied by the formation of other sulfur intermediate species, including S4O62− and SO32−. No evidence was found for the formation of elemental sulfur. Amorphous hematite (Fe2O3) and six-line ferrihydrite (5Fe2O3·9H2O) were the major components residing on the chalcopyrite surface, which were responsible for the slow dissolution rate at late stage. According to the present work, a model for the chalcopyrite dissolution mechanism in alkaline ammonium chloride solutions under ambient conditions is provided.

PH-dependent leaching mechanism of carbonatitic chalcopyrite in ferric sulfate solution

The dissolution of a carbonatitic chalcopyrite (CuFeS2) was studied in H2SO4−Fe2(SO4)3−FeSO4−H2O at varying pH values (0.5−2.5) and 25 °C for 12 h. Experiments were conducted with a size fraction of 53−75 µm. Low Cu recoveries, below 15%, were observed in all pH regimes. The results from the XRD, SEM−EDS, and optical microscopic (OM) analyses of the residues indicated that the dissolution proceeded through the formation of transient phases. Cu3.39Fe0.61S4 and Cu2S were the intermediate phases at pH 0.5 and 1.0, respectively, whereas Cu5FeS4 was the major mineral at pH 1.5 and 1.8. The thermodynamic modelling predicted the sequential formation of CuFeS2→ Cu5FeS4→Cu2S→CuS. The soluble intermediates were Cu5FeS4 and Cu2S, whilst, CuS and Cu3.39Fe0.61S4 were the refractory phases, supporting their cumulating behaviour throughout the dissolution. The obtained results suggest that the formation of CuS and Cu3.39Fe0.61S4 could contribute to the passive film formed during CuFeS2 leaching.

Cooperative extraction of metals from chalcopyrite by bio-oxidation and chemical oxidation

Chalcopyrite bio-dissolution plays an important role in the processing of copper sulfide ores. However, due to the slow dissolution rates of CuFeS2, bio-dissolution processes have not yet found widespread application. In order to enhance the dissolution of chalcopyrite, a novel method for enhancing the dissolution using ozone was proposed and verified. The generated products in chalcopyrite dissolution process in the presence of Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans was studied. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicate that a surface layer mainly consisting of jarosite and polysulfide (Snn−/S0) might be formed during biotic stage, which can be eliminated with the introduction of ozone. Electrochemical results show that ozone significantly increased the electrochemical reactivity of bioleached chalcopyrite, further proving that ozone enhanced the dissolution through destroying the surface layer. Hence, a bi-stage method for dissolution of chalcopyrite can be proposed.

Electrochemical investigation of microbially and galvanically leached chalcopyrite

The effect of the galvanic interaction between anodic chalcopyrite and cathodic pyrite was investigated by long-term electrochemical measurements of the galvanic coupling current and verified by chemical leaching and bioleaching. For the first time galvanic corrosion measurements (in the absence and in the presence of microorganisms) over days are reported. Combined microbial and galvanic leaching of chalcopyrite showed increased Cu recovery in the presence of pyrite. Corrosion resulted in mineral dissolution depending on multiple parameters (like metal corrosion). However, maximal chalcopyrite dissolution via bioleaching occurred in the presence of a large cathodic pyrite surface. Highest copper recovery was observed in case of high rest potential differences between galvanically coupled minerals (pyrite coupled with copper concentrate). A comparison of electrochemical data of this study with scientific literature revealed a wide range of rest potential data for a single metal sulfide. Fundamental research on galvanic interaction of mixed mineral systems need to focus on unified experimental parameters to allow a comparison.

Combined effect of silver ion and pyrite on AMD formation generated by chalcopyrite bio-dissolution

Chalcopyrite is a crucial contributor causing acid mine drainage (AMD). Silver and pyrite are commonly co-existed with chalcopyrite, and can significantly affect the copper release from chalcopyrite bio-dissolution process. However, the combined effect of them on chalcopyrite bio-dissolution has not been illustrated up to now. To fill this knowledge gap, the combined effect of silver and pyrite on chalcopyrite dissolution with Acidithiobacillus ferrooxidans was investigated in this study. The copper extraction reached the maximum value (62.3 ± 0.1%) with the presence of silver and pyrite, which was 43.8 ± 0.1% higher than the control group (without addition). This suggested more copper ions and acids were released under this circumstance. According to bio-dissolution results, SEM, XRD and XPS analyses, the promotion effect of silver and pyrite on chalcopyrite bio-dissolution was mainly attributed to the increase of ferric ions in solution and the reduction of passivation layer (Sn2−/S0) on chalcopyrite surface. The investigation into the bio-dissolution of chalcopyrite is important for controlling the generation of copper ions and acids. Silver or pyrite bearing chalcopyrite should be carefully treated to avoid the pollution of heavy metal copper and acid in the mining environment.

Control of the Redox Potential by Microcontroller Technology: Researching the Leaching of Chalcopyrite

The leaching of chalcopyrite under different redox potentials was studied with a redox potential controlling device based on microcontroller technology. The leaching test was carried out in a 500 mL flask with 4 g pure chalcopyrite and 200 mL sulfuric acid. The additional total Fe concentration was 0.1 mol/kg, and the initial pH was 0.7. Chalcopyrite leaching tests with initial redox potential of 400 mV and 600 mV (vs. Ag/AgCl, the same below) and controlled redox potential of 350 mV, 400 mV, 450 mV, 500 mV, and 600 mV were carried out at a temperature of 60 °C and a stirring speed of 300 rpm. The results showed that the dissolution of chalcopyrite could not be hindered until the granular intermediates (S0 and Sn2−) accumulated to a certain amount on the chalcopyrite surface. The main passivating species in chalcopyrite dissolution may be iron-deficient polysulfides. At 400 mV, the chalcopyrite passivation by polysulfides was overcome by the galvanic effect between pyrite and chalcopyrite, and the chalcopyrite was rapidly oxidized with Cu leaching rate reaching up to 32% in 7 h, while it was only 15% in the other experimental groups. However, at 450–500 mV, pyrite was oxidized and the galvanic effect between chalcopyrite and pyrite was destroyed, leading to a significant decrease in Cu leaching rate. When the redox potential was 600 mV, the dissolution of metal-deficient polysulfides was promoted; thus, the passivation was weakened.

Heap Bioleaching of Copper-Nickel Ores in the Arctic

This paper researches the effectiveness of heap leaching for processing the sulfide raw materials in Murmansk Oblast. It studies the kinetics of how metals are extracted into the solution, as well as the peculiarities of chalcopyrite dissolution. The paper shows that leaching destroys the grains, making them into fine particulate matter, which ultimately jeopardizes solution filtering. Use of recycled solution makes the leaching process more cost-effective.

DFT study of ferric ion interaction with passive layer on chalcopyrite surface: Elemental sulfur, defective sulfur and replacement of M2+(M=Cu and Fe) ions

The acidic dissolution of chalcopyrite in the sulfated medium is dependent on the rate of ferric (F3+) ion reduction. Due to the formation of elemental sulfur passive layer on the chalcopyrite surface, the ferric ion reduction rate decreases at the surface and prevents electron transfer from the surface to ferric ion. In this research, the interaction of ferric ion with sulfur passive layer in different modes has been studied using studio material software and density functional theory method. The results showed that the sulfur passive layer is insulated and ferric ion does not react on this surface, but the layer can be activated by changes in the structure. Defects in the passive layer structure (removal of sulfur atoms) or substitution of metal ions (iron and copper) cause surface reactivity, which by interaction with ferric ion will result in electron transfer to 3d orbital of Fe3+ ion. The overlap of 3p orbital surface sulfur atoms and the 3d orbital ferric ion conduction band provide the conditions for electron transfer. Also, the Fe3+ ion adsorption energies for different surface states, structure defects; ferrous and cupric ions substitution were obtained at −244, −229 and −228 kcal/mol, respectively. In addition, energy change (ΔE) due to the reduction of Fe3+ ion for structure defects more than the other two surfaces.