Chemical Leaching Of Chalcopyrite Research Articles

A Sulfur K-Edge XANES and Raman Study on the Effect of Chloride Ion on Bacterial and Chemical Leaching of Chalcopyrite at 25 °C

In the present study, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray absorption near edge structure (XANES) spectroscopy, and Raman spectroscopy were used to investigate the effect of chloride ions on chalcopyrite bioleaching and chemical leaching at 25 °C. The leaching results show that the addition of chloride ions suppressed the dissolution of chalcopyrite in both chemical and bacterial leaching. In chemical leaching, the solution redox potential in the experiment without Cl− stayed in a range more suitable for chalcopyrite dissolution compared with experiments with Cl−. In bioleaching, the bacteria activity was suppressed by Cl− leading to low dissolution rates of Cu. Surface morphology and chemical speciation studies confirmed the formation of potassium jarosite on the surface of the chalcopyrite leach residues. In addition, S K-edge XANES indicated the formation of trace amount of elemental sulfur and covellite on the mineral surfaces.

The Leaching Behaviours of Chalcopyrite with Distinct Genetic Types

The copper extraction yield from chemical leaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), as well as on the different genetic type of the chalcopyrite used. The chemical leaching characteristics of chalcopyrite from marine volcanic type and porphyry type were studied. It was found that the intermediates of marine volcanic chalcopyrite and porphyry chalcopyrite elucidated from the MLA were elemental sulphur and non-stoichiometric minerals, such as Cu3.5Fe4S2.5, Cu5Fe4S and Cu3.5Fe1.5S5. The results suggested that the main difference between marine volcanic chalcopyrite and porphyry chalcopyrite is the rates of copper and iron ions dissolution from chalcopyrite crystal lattice.

The Influence of pH and Ferrous Ions on Chalcopyrite Dissolution in Chemical Leaching Chalcopyrite

This paper studied the influence of pH, temperature and particle size on the chemical leaching of chalcopyrite. The results show that H+is not only responsible for the hydrolysis and precipitation of ferric ion as jarosite, but also related directly to chalcopyrite dissolution. The mechanism of chalcopyrite leaching is as follows: the first stage is H+attacking valence band and electron transition during oxidation, which needs a great deal of the energy to the system. The second stage is the transport of electrons from the chalcopyrite surface to the dissolved oxygen. However, the limiting step changes into diffusion control from chemical control when the elemental sulphur film formed, which obstructs transport of electrons.

硫酸水溶液による一次硫化銅精鉱の浸出に及ぼすｐＨおよび温度の影響

The chemical leaching of chalcopyrite was carried out to investigate the effects of temperature, ferrous ions and pH values on the leaching rate. The copper extraction of chalcopyrite attained 94% after 11 days when the initial pH value was 0.7 and the extraction temperature was 60 centigrade, while it was under 5% at pH 2.0. If the temperature was over 40 centigrade containing sufficient sulfuric acid, the passivation was not taken place which indicates increasing in the reaction temperature is one of the efficient ways to prevent from passivation occurrence. When the ferrous ions with the amount of 1.8 g/l was added (as initial) , the copper extraction was 93% after 5days at pH 0.7 and 60 centigrade. The extraction rate was faster by 2.6 times than the case of the extraction without ferrous ions. This is considered that high concentration of ferric ions oxidized from ferrous ions by dissolved oxygen worked as an oxidant for concentrate leaching. However, the high concentration of ferric ions seems to be an inhibitor for chalcopyrite chemical leaching when both initial pH and the temperature are low. When the pH value was controlled constantly, the higher dissolution rate was obtained at the lower pH range at over 40 centigrade. This shows sulfuric acid concentration plays a significant role in the chemical leaching of chalcopyrite. Moreover, when the temperature is less than 30 centigrade, passivation was taken place at pH controlled below 1.0; passivation occurs easier in the higher range of initial sulfuric acid concentration. Concerning passivation, some more research is necessary. We also examined leaching behavior of several kinds of chalcopyrite concentrates. The IOCG chalcopyrite leaching behavior seems to be similar with our leaching results mentioned right above but we found that there was a difference like leaching rate .This is considered that iron minerals were contained as impure compounds in respective chalcopyrite samples.

Kinetics of the bioleaching of chalcopyrite concentrate by acidophilic thermophile acidianus brierleyi

The kinetics of leaching of high-grade chalcopyrite (CuFeS(2)) concentrate (38-53 &mgr;m) by the acidophilic thermophilic bacterium, Acidianus brierleyi, was studied at 65 degrees C and pH 1.2 in a batch stirred reactor. The adsorption of A. brierleyi cells between the sulfide surface and solution was attained within the first 20 min of exposure to the mineral, and the equilibrium adsorption data were correlated with the Langmuir isotherm. The bioleaching was markedly accelerated in the presence of A. brierleyi, and greater than 90% leaching of copper in the concentrate was achieved within 10 days. The chalcopyrite leaching with A. brierleyi was found to take place with a direct attack by adsorbed cells on the mineral surface, the chemical leaching of chalcopyrite by ferric iron being insignificant. Rate data collected under a wide variety of operating variables were analyzed to determine kinetic and stoichiometric parameters for the microbial chalcopyrite leaching.

好酸性・好熱性細菌Ａｃｉｄｉａｎｕｓ ｂｒｉｅｒｌｅｙｉによる黄銅鉱の浸出

It is widely accepted in the area of hydrometallurgy that certain microorganisms play a major role in the leaching of base and precious metals from sulfide minerals. Most studies of bioleaching have dealt with the acidophilic mesophilic Thiobacillus species, which grow optimally at around 30 °C and low pH 1 ∼ 2. However, the acidophilic thermophiles, which have temperature optima for activity at 60 ∼ 70 °C, are also candidate microbes for accomplishing metal recovery from mineral resources. Little reports have appeared concerning the bioleaching of sulfides by the thermophilic bacteria at elevated temperatures. This paper describes the bioleaching of high-grade chalcopyrite concentrate (38 ∼ 53 μm) by the acidophilic thermophilic bacterium, Acidianus brierleyi, in a batch stirred reactor. The chalcopyrite leaching was markedly accelerated in the presence of A. brierleyi, and greater than 90 % leaching of copper in the concentrate was achieved at 65 °C within 10 days. However, the chalcopyrite concentrate was scarcely dissolved when the common leaching mesophile, Thiobacillus ferrooxidans, was used at 30 °C. Thus, the thermophile A. brierleyi could solubilize chalcopyrite much faster than the mesophile T. ferrooxidans. The rate of chalcopyrite leaching with A. brierleyi was unaffected by the initial concentration of ferric iron in leach solution, even when the rate of chemical leaching was dependent on the ferric iron concentration. This indicates that the bioleaching of chalcopyrite takes place with a direct microbial attack, the chemical leaching of chalcopyrite by ferric iron being insignificant. Leaching experiments with A. brierleyi were used to examine the dependence of leaching rate on three process parameters, such as solution pH (pH 1.0 ∼ 1.5), temperature (50 ∼ 75 °C), and initial concentrate-liquid loading ratio (2 ∼ 20 kg/m3). The chalcopyrite bioleaching in the batch reactor was carried out most satisfactorily at pH 1.2, 60 ∼ 65 °C, and initial chalcopyrite amount of 20 kg/m3.

Ｔｈｉｏｂａｃｉｌｌｕｓ ｆｅｒｒｏｏｘｉｄａｎｓによる黄銅鉱のバクテリアリーチングに及ぼすｐｈｏｓｐｈａｔｉｄｙｌｅｔｈａｎｏｌａｍｉｎｅの影響

Phospholipids such as phosphatidylethanolamine and phosphatidylglycerol are detected as extracellular substances in cultures of Thiobacillus ferrooxidans and Thiobacillus thiooxidans, but their effect on bacterial leaching is not well understood. In this paper, basic experiments on bacterial leaching of chalcopyrite by Thiobacillus ferrooxidans were carried out in the presence of phosphatidylethanolamine.The copper extraction in chemical leaching of chalcopyrite with ferric sulfate increased slightly by the addition of phosphatidylethanolamine. In the medium containing ferrous sulfate as substrate, the ferrous oxidation by Thiobacillus ferrooxidans and its growth were not affected by the addition of phosphatidylethanolamine. In bacterial leaching, the addition of phosphatidylethanolamine had no effect on the copper extraction and bacteria adsorption on the mineral surfaces. These results were different from the results with phosphatidylglycerol.

Enhancement in Bacterial Leaching of Chalcopyrite by Polyoxyethylene Sorbitan Monolaurate Addition.

The effect of surfactant addition on bacterial leaching of chalcopyrite by Thiobacillus ferrooxidans was investigated with polyoxyethylene sorbitan monolaurate (Tween20) as a surfactant. Bacterial leaching experiments were carried out without nutrient mineral salts such as ammonium sulfate to avoid the complication of leaching behavior with cell growth. Without the surfactant, most cells adhered to the mineral surface and soluble iron was dominantly present in ferrous form. The surfactant depressed the cell adhesion to the mineral surface and the number of cells in the liquid phase increased with increasing addition. When adding 20 to 50g/m3 of the surfactant, the cells in the liquid phase rapidly oxidized ferrous ions to form ferric ions and chalcopyrite was chemically oxidized by the ferric ions, as a result the amount of extracted copper increased markedly. However, the excessive addition depressed the bacterial ferrous oxidation and the chemical leaching of chalcopyrite with ferric ions, and decreased copper extraction.

The leaching of chalcopyrite with cupric chloride

A comparative study of electrochemical leaching and chemical leaching of chalcopyrite was performed mainly at 343 K to elucidate the leaching mechanism of chalcopyrite with CuCl2. Also, the morphology of the leached chalcopyrite surface was studied by using a single chalcopyrite crystal. The leaching with CuCl2 produced a porous elemental sulfur layer on the chalcopyrite surface, showing a similar morphology to that produced during leaching with FeCl3. The leaching kinetics were found to be linear over an extended period, followed by an acceleration stage, as a result of an increase in the reaction surface area. The leaching rate of chalcopyrite was proportional to C(CuCl2)0.5, whereas it was inversely proportional to C(CuCl)0.5. The mixed potential of chalcopyrite exhibited a 66 mV decade−1 dependency upon C(CuCl2), and—69 mV decade−1 upon C(CuCl). Based on these observations together with other findings, an electrochemical mechanism involving the oxidation of chalcopyrite and CuCl − 2 and the reduction of CuCl+ was proposed. The Tafel plot between the mixed potential and the current density obtained by converting the rate of chemical leaching gave a straight line whose slope was in good agreement with that of the electrochemical leaching. These findings strongly support the electrochemical mechanism of chalcopyrite leaching with cupric chloride.

Anodic dissolution of n-type and p-type chalcopyrite

The anodic dissolution of n- and p-type chalcopyrite (CuFeS2) was studied in both acidic sulphate and acidic chloride media under conditions relevant to chemical leaching, i.e., at temperatures >70° C and over the potential region 0.2–0.6 V versus SCE. Double potential pulse chronoamperometry was used to probe the surface of the chalcopyrite anodes to determine the activation currents at various applied overpotentials. Analysis of the data obtained in both systems indicated the formation of a surface layer, a solid electrolyte interphase (SEI), which slows the rate of electron transfer. The electron transfer between various redox couples, including Cu2+/Cu2+, Fe2+/Fe2+ and I3−/I− on n- and p-type chalcopyrite and on Pt, was compared using cyclic voltammetry. In the potential region of interest, the Fe2+/Fe2+ couple is much less reversible on chalcopyrite than are the Cu2+/Cu2+ and I3−/I− redox couples. Chemical leaching of chalcopyrite in the presence of various oxidants was also carried out, and the results of the chemical experiments were discussed in terms of the electrochemical properties of the systems.