Interaction of pentlandite,chalcopyrite, and pyrrhotine with elementary sulfur: III. Sulfidizing of nickel-containing pyrrhotine

The sulfidizing of the main sulfide minerals of copper-nickel ores, namely, pentlandite, chalcopyrite, and pyrrhotine, by elementary sulfur is studied. The phase compositions of the sulfidizing products are examined by scanning electron microscopy and electron-probe microanalysis, and a mechanism is proposed for the sulfidizing of nickel-containing pyrrhotine under near-equilibrium conditions.     

Interaction of pentlandite,chalcopyrite, and pyrrhotine with elementary sulfur: I. Sulfidizing of pentlandite

The first part of the study into the sulfidizing of the major minerals of copper-nickel ores, namely, pentlandite, chalcopyrite, and pyrrhotine, by elementary sulfur is presented. The phase composition of the sulfidizing products is determined by scanning electron microscopy and electron-probe microanalysis and is then used to propose a mechanism for the sulfidizing of pentlandite under near-equilibrium conditions.     

Galvanic conversion of chalcopyrite

Galvanic interaction between particulate chalcopyrite (CuFeS₂) and copper results in the rapid conversion of chalcopyrite to chalcocite. The effects of temperature, surface area, concentration of sulfuric acid and agitation were systematically evaluated. The kinetics were found to be controlled by a steady-state current flow controlled by the effective anodic and cathodic surface areas involved in the galvanic couple. The experimental activation energy was 11.5 and stoichiometric data and reaction products have been characterized. The overall kinetic system has been evaluated based upon an electrochemical model.     

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.     

Morphology of chalcopyrite leaching in acidic ferric sulfate media

Two-dimensional computer simulations based on percolation theory were used to explain the morphology associated with atmospheric chalcopyrite leaching in acidic ferric sulfate solution. The aim of this study was to understand the differences in observed morphology between chalcopyrite residues leached with and without pyrite in the leach environment. The study of chalcopyrite morphology is of interest because there are no records of similar investigations available. Simulations showed high copper extractions from chalcopyrite when surface atoms were mobile leading to agglomeration of like atoms and the formation of highly porous mineral structures. High degrees of surface mobility are associated with active anodic behavior. The simulated morphology was consistent with previously observed residue morphology from chalcopyrite leach experiments in the presence of pyrite. Thus it was found that the enhanced recoveries and peculiar morphology observed during pyrite catalyzed leaching are attributable to active anodic behavior. Conversely, the simulations also showed that the recovery of copper was low when surface atoms were effectively locked in place resulting in mineral passivation. The simulation morphology obtained in this case was also consistent with experimental results of chalcopyrite leached without the presence of pyrite which have shown non-porous film like product layers.     

Thermodynamic investigations on chalcopyrite

The vapor pressures of sulfur in equilibrium with various compositions within the Cu?Fe?S system were measured by a molecular absorption technique. Measurements were made as functions of temperature for the single phase compositions CuFeS_1.62, CuFeS_1.70, CuFeS_1.80 and CuFeS_1.90, for the two-phase fields bornite+chalcopyrite and pyrrhotite+chalcopyrite, and for the three-phase field chalcopyrite+bornite+pyrite. Statistical mechanical equations are derived and used to evaluate the data. Chalcopyrite highly deficient in sulfur behaves similarly to an ideal mixture of Cu₂S and FeS with a random distribution of the constituent cations. Calculated values are given for the Gibbs energy of formation of chalcopyrite at 973 K for compositions CuFeS_1.62 to CuFeS₂, and the entropies and Gibbs energies of formation for CuFeS₂(s) from 800 to 1000 K. Standard entropies, enthalpies, and energies are derived: S⁰ _{CUFeS 2} (298)=32 e.u., ΔH⁰ _{CuFeS 2},f(298)=?42,116 cal, ΔG⁰ _{CuFeS 2} f (298)=?42,800 cal.     

山东招远玲珑金矿田黄铜矿特征研究

玲珑金矿田矿石中黄铜矿为主要载金矿物之一，电子探针分析结果和电子显微镜下X射线面分布特征均证明黄铜矿为主成矿阶段的产物，研究黄铜矿的标型特征对指导找矿具有重要的意义。     

The leaching of chalcopyrite with ferric sulfate

The leaching kinetics of natural chalcopyrite crystals with ferric sulfate was studied. The morphology of the leached chalcopyrite and the electrochemical properties of chalcopyrite electrodes also were investigated. The leaching of chalcopyrite showed parabolic-like kinetics initially and then showed linear kinetics. In the initial stage, a dense sulfur layer formed on the chalcopyrite surface. The growth of the layer caused it to peel from the surface, leaving a rough surface. In the linear stage, no thick sulfur layer was observed. In this investigation, chalcopyrite leaching in the linear stage was principally studied. The apparent activation energy for chalcopyrite leaching was found to range from 76.8 to 87.7 kJ mol⁻¹, and this suggests that the leaching of chalcopyrite is chemically controlled. The leaching rate of chalcopyrite increases with an increase in Fe(SO₄)_1.5 concentration up to 0.1 mol dm⁻³, but a further increase of the Fe(SO₄)_1.5 concentration has little effect on the leaching rate. The dependency of the mixed potential upon Fe(SO₄)_1.5 concentration was found to be 79 mV decade⁻¹ from 0.01 mol dm⁻³ to 1 mol dm⁻³ Fe(SO₄)_1.5. Both the leaching rate and the mixed potential decreased with an increased FeSO₄ concentration. The anodic current of Fe(II) oxidation on the chalcopyrite surface in a sulfate medium was larger than that in a chloride medium.     

Leaching of chalcopyrite with ferric ion. Part I: General aspects

This paper presents a review of the literature on chalcopyrite leaching with ferric sulphate in acid medium. The effects of several parameters (ferric salt anion, oxidant concentration, pH and temperature) are examined and possible explanations are offered for the passivation of this sulphide during dissolution. The main theories related with chalcopyrite passivation point to the formation of a diffusion layer surrounding the chalcopyrite during dissolution, consisting of: bimetallic sulphide, copper polysulphide with a deficit of iron with respect to chalcopyrite, and elemental sulphur. Recent studies suggest that ferric ion plays two important and opposite roles in this process: as a mineral oxidizing agent and as the agent responsible for chalcopyrite passivation.     

Chlorination of chalcopyrite concentrates

The chlorination behaviors of two chalcopyrite concentrates and their pure constituents in Cl₂+N₂ were investigated by thermogravimetric analysis (TGA) in nonisothermal conditions up to 1000 °C. The effect of temperature on the reaction of chlorine with both concentrates was studied between 170 °C and 300 °C under isothermal conditions. The effects of gas flow rate, chlorine content of the gas mixture, and reaction time on the reaction rate were also investigated. The reaction products were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results showed that the kinetics of chlorination of chalcopyrite concentrates generating chlorides of Cu, Pb, Zn, Fe, and S was rapid at about 300 °C. The iron and sulfur chlorides were volatilized, leading to a residue containing valuable metal chlorides.     

外控电位法浮选分离黄铜矿和辉钼矿

利用自制外控电位浮选槽研究了矿物粒度、矿浆pH值、外控电位大小等因素对黄铜矿和辉钼矿浮选行为的影响, 从而找到二者分离的条件并进行了铜钼混合精矿的外控电位浮选分离, 采用循环伏安测试和腐蚀电偶测试验证了上述试验结论. 研究结果表明, -150+31 μm的黄铜矿受外控电位影响大, 容易被抑制, 而辉钼矿则不容易被抑制. -31 μm的黄铜矿和辉钼矿可浮性均较差, 受外控电位影响较小. 外控电位浮选在碱性条件下进行有利于实现抑铜浮钼. 在pH值11的条件下, 抑铜浮钼的最佳分离外控电位为-1100~-700 mV(vs Ag/AgCl). 在pH值为11、外控电位-800 mV(vs Ag/AgCl)的条件下对多宝山铜钼混合精矿进行浮选分离, 经过一次浮选分离可得到钼回收率80.57%、铜回收率10.19%的钼粗精矿, 辉钼矿和黄铜矿的浮游差达到70.38%, 这使外控还原电位下浮选分离黄铜矿和辉钼矿成为可能. 另外, 腐蚀电偶测试结果表明: 黄铜矿和辉钼矿间的电偶腐蚀对于抑铜浮钼浮选有促进作用.      

The leaching of chalcopyrite with ferric chloride

A comparative study of electrochemical leaching and chemical leaching of chalcopyrite was done to elucidate the leaching mechanism of chalcopyrite with FeCl₃. The leaching rate of chalcopyrite exhibits a half order dependency on the FeCl₃ concentration, whereas it is independent of the FeCl₂ concentration. The mixed potential of chalcopyrite exhibits a 72 mV · decade⁻¹ dependency upon FeCl₃ concentration; no influence on the mixed potential was observed by the addition of FeCl₂. In FeCl₃ solutions acidified with HC1, the predominant chemical species of Fe(III) was found to be FeCl ₂ ^u+ from equilibrium calculations. The concentration of this species is approximately proportional to the amount of FeCl₃ added to the solutions. Based on these observations, an electrochemical mechanism is proposed which involves the oxidation of chalcopyrite and the reduction of FeCl ₂ ⁺ , the predominant species of Fe(III). By converting the leaching rate to electric current density,i, 140 mV · decade⁻¹ dependency of mixed potential,E, against logi is obtained. This dependency of the chemical leaching of chalcopyrite with FeCl₃ as well as its activation energy agree with those for electrochemical leaching. These findings strongly support the electrochemical mechanism of FeCl₃ leaching of chalcopyrite. Formerly Graduate Student, Kyoto University     

不同因素对黄铜矿、黄铁矿浮选分离动力学影响的研究

以动力学参数K（浮选速率系数）为依据,来评判黄铜矿、黄铁矿快速浮选分离的可能性.首 先,在不同矿浆浓度、浮选粒度及浮选机转速等条件下考察黄铜矿和黄铁矿纯矿物K值的变化,在一 定程度上阐释了黄铜矿、黄铁矿快速浮选分离的动力学机理及其可能性;同时,为使黄铜矿、黄铁矿快 速浮选分离技术在工业上具有适用性,进一步研究黄铜矿与黄铁矿组成的2种粒级的混合矿在适当 浮选条件下的动力学特性.结果表明,适当的浮选条件,可扩大黄铜矿与黄铁矿之间的浮选速率差异,从而实现黄铜矿的快速优先浮选.      

Leaching studies of chalcopyrite and sphalerite with hypochlorous acid

Laboratory studies have been conducted on the leaching of chalcopyrite and sphalerite with hypochlorous acid. The effects of stirring speed, temperature, pH, and hypochlorous acid concentration on the leaching rates have been determined. In addition, the leaching mechanisms have been resolved by analyzing the concentrations of the reaction products. It has been found that more than 90 pct extraction of both chalcopyrite and sphalerite can be achieved in one hour using less than 0.3 molar hypochlorous acid at room temperature. The primary leach products of chalcopyrite and sphalerite were sulfur and sulfate in the mole ratios of 1 to 1 and 2 to 1, respectively. A mixed kinetic model was applied to explain the leaching rates of chalcopyrite while a diffusion model was applied to explain the leaching rates of sphalerite. The mixed kinetic model involved steady-state diffusion of hypochlorous acid through the sulfur layer by a chemical reaction at the reaction interface. Good agreement between these models and the leaching rates of both minerals was obtained.     

Reactivity comparison of Australian chalcopyrite concentrates in acidified ferric solution

The leaching of chalcopyrite from several Australian chalcopyrite concentrates by the reaction CuFeS₂ + 4 Fe(III) + Cu(II) + 5 Fe(II) + 2 S⁰ obeyed parabolic kinetics in acidified nitrate solution between 25 and 40°C. The chalcopyrite reactivity was dependent on the mineral composition of the concentrate: the presence of pyrite accelerated the reaction markedly, but sphalerite and bismuthinite slowed it slightly. Galvanic interaction between minerals cannot account for this change: instead, the associated minerals must influence the rate determining diffusion of the lattice elements within the chalcopyrite crystal.     

Ferric chloride leaching of sulphidized chalcopyrite

Reactions between chalcopyrite and elemental sulphur at between 320°C and 400°C produce various combinations of covellite, nukundamite (Cu_5,5 FeS_6,5, and pyrite depending on the sulphur content of the products. If all the contained copper is transferred to covellite, and iron to pyrite, at least 95% of the copper can be leached by ferric chloride with negligible iron dissolution at up to 70°C. At above 70°C, iron is extracted from pyrite. When nukundamite is present, the iron and copper contents of this compound are leached simultaneously, and the consequent loss of selectivity is further enhanced at above 70°C by attack of pyrite. The increased rates of copper extraction obtained following sulphidation result from both the breakdown of chalcopyrite and a greater porosity.     

Sulfidation of chalcopyrite with elemental sulfur

The sulfidation of chalcopyrite concentrate with elemental sulfur was studied in the temperature range of 325 °C to 500 °C. The effects of temperature, time, and composition of the reactants on the sulfidation were determined. The X-ray diffraction (XRD) and light microscopic analyses showed that the sulfidation of chalcopyrite forms CuS and FeS₂ at temperatures below 400 °C. However, at temperatures above 400 °C, Cu₅FeS₆ and FeS₂ were formed. The sulfidation of chalcopyrite proceeds mainly through the gaseous phase, and temperature has a significant influence on the sulfidation rate in the range of 325 °C to 400 °C. The extraction of copper from the reacted material was determined by leaching in an H₂SO₄-NaCl-O₂ system. Over 90 pct of copper could be extracted by leaching at 100 °C for 60 minutes in the mentioned system.     

Galvanic interaction between chalcopyrite and pyrite during bacterial leaching of low-grade waste

The bacterial leaching of a low-grade chalcopyrite waste rock in a lixiviant containing thermophilic, Sulfolobus-like microorganisms at 60°C and a lixiviant containing Thiobacillus ferrooxidans at 28°C has been compared with the leaching in sterile lixiviant in terms of copper solubilized in elapsed time and the conversion of $\text{Fe}{}^{\mathrm{3+}}\text{Fe}{}^{\mathrm{2+}}$. Bacterial action has been shown to drastically increase the ratio $\text{Fe}{}^{\mathrm{3+}}\text{Fe}{}^{\mathrm{2+}}$ with elapsed time of leaching. Direct observations of the associated pyrite and chalcopyrite surface corrosion, utilizing scanning electron microscopy, showed that during the leaching of these sulfides as separate, non-contacting phases, the pyrite corroded more rapidly than the chalcopyrite in both sterile and inoculated media. This effect was more pronounced at elevated temperature and in the presence of bacteria. When the pyrite and chalcopyrite were in contact, the resulting galvanic interaction caused the chalcopyrite to corrode more rapidly than the pyrite, which was effectively passivated. The leaching of chalcopyrite is thereby enhanced in contact with pyrite. This effect is accelerated in the presence of bacteria. The corrosion of chalcopyrite was also markedly enhanced as a result of the oxidation of elemental sulfur (formed during the reaction) to sulfuric acid. This reaction was also accelerated by bacterial catalysis. The important implications of the enhanced chalcopyrite corrosion by galvanic interaction in the leaching of low-grade chalcopyrite waste and other galvanic-contact regimes involving metal sulfides are identified and discussed.     

Review of the hydrometallurgy of chalcopyrite concentrates

Abstract

A critical appraisal has been made of methods that have been proposed for the hydro metallurgical treatment of chalcopyrite concentrates. Those methods in which the primary breakdown of chalcopyrite is effected by leachants are discussed. Methods in which leaching is preceded by pyrometal-lurgical decomposition of the mineral include selective sulphation and nonoxidizing treatments in which the ratios of copper, iron and sulphur are changed. No process has yet been found that can replace conventional pyrometallurgical processing, although several have reached the pilot plant stage. The incentives for devising an economic hydrometallurgical process for extracting copper from sulphide ores are the avoidance of air pollution and the possibility of recovering iron, elemental sulphur and other nonferrous metals.

Résumé

Une appréciation critique a été faite des méthodes proposees pour le traitement hydrométallurgique des concentrés de chalcopyrite. Les méthodes par lesquelles la deécomposition originale de la chalcopyrite est affectée par les lixiviants, sont décrites. Les méthodes selon lesquelles la lixiviation est précédée par la décomposition pyrométa1lurgique du minerai comprennent la sulphatation sélective et les traitements non-oxydants dans lesquels les concentrations relatives de cuivre, fer et souffre sont changées. Aucun procédé pouvant remplacer les procédés pyrométallurgiques conventionnels n'a encore été trouvé, bien que plusieurs soient parvenus au stade de l'exploitation sur pilote. L'intérêt d'un procédé hydrométallurgique économique, pour l'extraction du cuivre, à partir des minerais de souffre, serait la non-pollution de l'air et la possibilité de récupération du fer, du souffre élémentaire et des autres métaux non-ferreux.     

The electroleaching of bornite and chalcopyrite

The electroleaching reactions of bornite and chalcopyrite have been investigated by a study of the anode-potential/time relationships and examination of the products by electron microprobe analysis and X-ray diffraction, with particular reference to current and energy efficiencies. The effects of solution composition, temperature and current density on the reactions have been studied.For bornite the results indicate that for maximum current and energy efficiencies the optimum conditions include: (1) high temperature (certainly > 60°C ); (2) low current density, and (3) the presence of chloride ions in the electrolyte.For chalcopyrite these conditions also appear to be optimal, and, in addition, the reduction of acid concentration for chloride solutions is advantageous.Comparison with previous work on the simple copper sulphides shows that for the treatment of any copper-iron sulphide or copper sulphide ore similar electroleaching conditions should prevail.