Effect of suspension potential on the oxidation rate of copper concentrate in a sulfuric acid solution

A chalcopyrite concentrate containing 17 pct pyrite was oxidized in 1 mol/dm³ sulfuric acid solution at 90 °C (363.2 K). The suspension potential (Ptvs SCE, in the presence of Fe³⁺/Fe²⁺) was maintained constant in the range 0.30 to 0.65 V by controlled additions of KMnO₄ solution. The oxidation appeared to be under surface reaction control. The rate constant was nearly independent of total Fe concentration (0.01 to 0.5 mol/dm³), but increased rapidly with a rise in suspension potential until it reached a maximum at 0.40 to 0.43 V, after which there was marked decrease at around 0.45 V. Chalcopyrite in the concentrate was oxidized to form elemental sulfur over the whole of the suspension potential range, whereas the oxidation of pyrite took place only above 0.45 V and yielded sulfate ion. At 0.40 V the apparent activation energy was 47 kJ/mol. An analogy between the potential dependence of the rate and the Tafel correlation for an electrode process is discussed.     

Reaction mechanism for the acid ferric sulfate leaching of chalcopyrite

The acid ferric sulfate leaching of chalcopyrite, CuFeS₂ + 4Fe⁺³ = Cu⁺² + 5Fe⁺² + 2S⁰ was studied using monosize particles in a well stirred reactor at ambient pressure and dilute solid phase concentration in order to obtain fundamental details of the reaction kinetics. The principal rate limiting step for this electrochemical reaction appears to be a transport process through the elemental sulfur reaction product. This conclusion has been reached in other investigations and is supported by data from this investigation in which the reaction rate was found to have an inverse second order dependence on the initial particle diameter. Furthermore, the reaction kinetics were found to be independent of Fe⁺³, Fe⁺², Cu⁺² and H₂SO₄ in the range of additions studied. The unique aspect of this particular research effort is that data analysis, using the Wagner theory of oxidation, suggests that the rate limiting process may be the transport of electrons through the elemental sulfur layer. Predicted reaction rates calculated from first principles using the physicochemical properties of the system (conductivity of elemental sulfur and the free energy change for the reaction) agree satisfactorily with experimentally determined rates. Further evidence which supports this analysis includes an experimental activation energy of 20 kcal/mol (83.7 kJ/mol) which is approximately the same as the apparent activation energy for the transfer of electrons through elemental sulfur, 23 kcal/ mol (96.3 kJ/mol) calculated from both conductivity and electron mobility measurements reported in the literature. formerly Metallurgy Graduate Student, University of Utah.     

A multifactor simulation of the process of leaching oxidized molybdenum products in sulfuric acid solutions

The extraction of molybdenum into a solution upon roasting the middling is investigated using the mathematical planning method for the experiment. Partial and generalized formulas of the degree of Mo extraction by the Protod’yakonov equation are obtained. This equation is corrected, allowing for a limitation of the degree of reaction (no higher than 100%), by being introduced into the exponent. The value of the activation energy is calculated. It is shown that the limiting stage is diffusion.     

铁闪锌矿在硫酸浸出过程中的电化学行为

为研究铁闪锌矿氧化浸出机理,以人工合成铁闪锌矿的悬浮矿浆为研究对象,采用三电极体系对其在硫酸浸出过程中的电化学行为进行了研究.结果表明在铁闪锌矿浸出过程中有H₂S中间产物生成;通氧、元素硫分散剂以及氯离子引入浸出体系均能明显促进铁闪锌矿的电化学氧化;随硫酸浓度升高,铁闪锌矿的电化学氧化不断加强而闪锌矿的电化学氧化受抑.与闪锌矿相比,铁闪锌矿更易发生电化学氧化.在铁闪锌矿硫酸浸出过程中,其电化学氧化作用不容忽视.     

Galvanic interaction between chalcopyrite and manganese dioxide in sulfuric acid medium

Dissolution of chalcopyrite and managanese dioxide minerals in the presence of each other in sulfuric acid medium was studied using compact disc electrodes of the minerals under various H₂SO₄ concentrations (0.05 to 0.5 M). [H⁺] had a positive effect on the reaction rate. Strong galvanic interaction was observed to take place between chalcopyrite and manganese dioxide, the galvanic interaction predominating over the individual dissolution (self-corrosion) rates. Evans diagrams constructed from polarization curves of the two minerals were helpful in interpreting the leaching data. The electrochemical nature of the dissolution reaction was analyzed through application of the Butler-Volmer equation and was confirmed from polarization measurements conducted with the respective mineral electrodes.     

Enhancement of chalcopyrite leaching by ferrous ions in acidic ferric sulfate solutions

The effects of ferrous ions on chalcopyrite oxidation with ferric ions in 0.1 mol dm⁻³ sulfuric acid solutions were investigated by leaching experiments at 303 K in nitrogen. With high cupric ion concentrations, the chalcopyrite oxidation was enhanced by high concentrations of ferrous ions and copper extraction was mainly controlled by the concentration ratio of ferrous to ferric ions or the redox potential of solutions. Ferrous ions, however, suppressed the chalcopyrite oxidation when cupric ion concentrations were low. A reaction model, which involves chalcopyrite reduction to intermediate Cu₂S by ferrous ions and oxidation of the Cu₂S by ferric ions, was proposed to interpret the results.     

Kinetics of silver leaching from manganese-silver associated ores in sulfuric acid solution in the presence of hydrogen peroxide

Kinetics of silver leaching from a manganese-silver associated ore in sulfuric acid solution in the presence of H₂O₂ has been investigated in this article. It is found that sulfuric acid and hydrogen peroxide have significant effects on the leaching rate of silver. The reaction orders of H₂SO₄ and H₂O₂ were determined as 0.80 and 0.68, respectively. It is found that the effects of temperature on the leaching rate are not marked, the apparent activation energy is attained to be 8.05 kJ/mol within the temperature range of 30 °C to 60 °C in the presence of H₂O₂. Silver leaching is found to be diffusion-controlled and follows the kinetic model: 1−2x/3−(1−x)^2/3=Kt. It is also found that particle size presents a clear effect on silver leaching rate, and the rate constant (k) is proportional to d ₋₂ ⁰ .     

P204从高铝粉煤灰硫酸浸液中萃取除铁

主要针对高铝粉煤灰酸浸液中铁铝萃取分离性能进行研究,通过模拟高铝粉煤灰酸浸液(C(Al3+)=37.1 g/L,C(Fe3+)=5.1 g/L),采用P204+260#溶剂油萃取体系,对组成液中铁铝进行萃取分离,系统研究了P204体积分数、温度、反应时间、溶液初始pH值、相比V(O):V(A)等因素对萃取和反萃的影响,...     

Leaching of chalcopyrite with ferric ion. Part II: Effect of redox potential

This paper reports the effect of redox potential (or Fe³⁺/Fe²⁺ ratio) on chalcopyrite leaching. The relationship between redox potential and other variables (iron concentration and temperature) is also evaluated. Leaching tests were performed in stirred Erlenmeyer flasks with 0.5 g of pure chalcopyrite and 100 mL of a Fe³⁺/Fe²⁺ sulphate solution. The redox potential ranged between 300 and 600 mV Ag/AgCl for the solution at a pH 1.8, 180 rpm, with temperatures at 35 °C or 68 °C. The results show that although ferric ion is responsible for the oxidation of chalcopyrite, ferrous ion has an important role in that it controls precipitation and nucleation of jarosites, which ultimately causes passivation of this sulphide. Chalcopyrite dissolves through the formation of an intermediary product (covellite, CuS) that is later oxidized by ferric ion, releasing Cu²⁺ ions.     

微波辅助硫酸浸出红土镍矿的研究

以红土镍矿为原料,研究了微波辅助硫酸浸出镍钴的工艺条件。考察了硫酸浓度、微波功率、微波温度、辐射时间、液固体积质量比对镍钴浸出率的影响。结果表明,在硫酸浓度3.0mol/L、微波功率700 W、微波温度90℃、辐射时间2.5 h、液固体积质量比4:1的最佳工艺条件下,镍浸出率达91%,钴浸出率65%以上。     

Leaching of chalcopyrite with ferric ion. Part III: Effect of redox potential on the silver-catalyzed process

This study examines the effect of redox potential on silver-catalyzed chalcopyrite leaching. Leaching tests were carried out in stirred Erlenmeyer flasks with 0.5 g chalcopyrite mineral, 1 g Ag/kg Cu and 100 mL of a sulphate solution of Fe³⁺/Fe²⁺ (with redox potential ranging between 300 and 600 mV Ag/AgCl) at pH 1.8, 180 rpm and 35°C or 68 °C. Unlike uncatalyzed leaching, an increase of the redox potential increased copper dissolution in the presence of silver ions, as the regeneration of Ag⁺ requires a high concentration of oxidizing agent, Fe³⁺. Additionally, the high reactivity of the mineral surface when silver was present could have been responsible for inhibiting the nucleation of hydrolysis products of Fe³⁺ on it. Excessive addition of silver transformed the chalcopyrite surface into copper-rich sulphides such as covellite, CuS, and geerite, Cu₈S₅, preventing the formation of CuFeS₂/Ag₂S galvanic couple and the recycling of silver ions.     

Effect of the trivalent iron content in a pyrrhotine concentrate on the reaction mechanism of its sulfuric acid leaching

The laws of atmospheric sulfuric acid leaching of pyrrhotine concentrate are analyzed as a function of the redox potential of a reaction system, which is determined by the Fe(III) content in a solution.     

氯化物浸出黄铜矿的试验研究

研究了硝酸催化氧化、氯化物浸出黄铜矿的机理,考察了氧化和浸出反应的影响因素。研究结果表明:硝酸催化氧化的优化条件是酸度0.50mol/L、温度95℃、硝酸量0.5%～1.0%。采用浸出、氧化分离式新工艺,4.5h铜的浸出率达97%,氧化除铁率97%,可实现黄铜矿浸出的综合优化。     

Simultaneous leaching of a deep-sea manganese nodule and chalcopyrite in hydrochloric acid

Hydrochloric acid leaching of chalcopyrite and a manganese nodule, in combination, was studied using powder samples. Chalcopyrite, which does not dissolve well in HCl, was effectively leached in the presence of a manganese nodule at 3 to 4 M HCl. The rates of dissolution of metal values from the nodule were also enhanced in the presence of chalcopyrite. Dissolution was found to occur through three routes: (1) the galvanic interaction between CuFeS₂ and MnO₂, (2) the action of the Fe³⁺/Fe²⁺ redox couple, and (3) the action of Cl₂ gas generated from the MnO₂-HCl reaction on CuFeS₂. The last route appeared to make the major contribution to the dissolution. The combined leaching of a nodule and chalcopyrite appears to be promising from both technical and economic points of view.     

氯化物浸出黄铜矿的试验研究

研究了硝酸催化氧化、氯化物浸出黄铜矿的机理，考察了氧化和浸出反应的影响因素。研究结果表明：硝酸催化氧化的优化条件是酸度。0．50mol／L、温度95℃、硝酸量0．5％～1．0％。采用浸出、氧化分离式新工艺，4．5h铜的浸出率达97％，氧化除铁率97％，可实现黄铜矿浸出的综合优化。     

A simple kinetic model for sulfuric acid leaching of copper from chrysocolla

Experimental results obtained in room temperature laboratory leaching studies of lowgrade chrysocolla are interpreted by a kinetic equation of the form 1?(1?R)^1/3=(1/αKr _c) ln (αkKC ₀t+1) derived on the basis of a special form of the shrinking-core model and assuming chemical-reaction control. The experimental program encompasses a large range of particle sizes and reaction times and significantly extends previous experimental data on similar ore systems. The kinetic model, shown to be consistent with the experimental data, assumes the ore-particle structure to be characterized by pores and channelized regions which extend from the outer surface through a reacted zone into the unreacted core. Scanning electron microscope observations of unreacted particle surfaces as well as reacted particle surface structures lend support to this concept of leaching. The reaction rate is observed to vary inversely with initial mean particle radius, and diffusion in any form appears to be negligible by comparison with surface reaction phenomena.     

Sorption behavior of cobalt in sulfuric acid solutions

Interaction of cobalt(II) ions with functional groups of sorbents based on amines, which additionally contain carboxyl (ANKB-35) and hydroxyl (SB-1, AN-31) fragments, is investigated. It is shown that the form of existence of the sorbent exerts an insignificant effect on cobalt absorption with ampholyte ANKB-35. Alternatively, anion exchangers AN-31 and SB-1 sorb cobalt in noticeable amounts only in the deprotonated form (OH^?). The analysis of obtained results on the cobalt sorption in equilibrium conditions as well as the IR spectroscopy provides clarification of specific features of the process. It is found that cobalt is adsorbed owing to the complex formation with nitrogen of amino groups of sorbents with the additional formation of bonds with carboxyl (ANKB-35) and hydroxyl (AN-31, SB-1) groups. In addition, the process is complicated by precipitation in the phase of sorbents according to the scheme Co²⁺ → Co(OH)₂ → Co(OH)₃. This effect is especially characteristic of the SB-1 anion exchanger, which contains a considerable amount of hydroxyl groups. The obtained data provide a justified choice of the ion exchanger and conditions of its use to concentrate Co²⁺ from solutions of sulfuric acid leaching of various cobalt-containing raw materials.     

Leaching chalcopyrite with sodium chlorate in hydrochloric acid solution

Abstract

Sodium chlorate was used as an oxidant for the chalcopyrite leaching in a hydrochloric acid solution. The hydrochloric acid concentration has an important effect on the dissolution of chalcopyrite. The results indicate that stirring speed has a negligible effect on copper dissolution, suggesting that the reaction is not controlled by liquid phase diffusion. Chalcopyrite leaching is also affected by temperature. X-ray diffraction studies show that sulphide is oxidised to sulphate at temperatures less than or equal to 65°C, and at 85°C, it is oxidised to elemental sulphur during the leaching process. Studies of the effect of temperature on dissolution indicate that the leaching process is highly dependent on temperature for the range of 25–65°C. This result is consistent with the values for the activation energy at 25–45°C (60·0 kJ mol^?1) and 45–65°C (57·7 kJ mol^?1). Within these temperature ranges, the leaching process is controlled by a chemical reaction. However, at temperatures of 65–85°C, the activation energy in (0–180 min) is 28·17 kJ mol^?1, which suggests that the reaction is diffusion and chemically controlled during this stage. During the last stage (180–300 min) of the process at 65–85°C, the activation energy is only 0·55 kJ mol^?1. At this point, it appears that diffusion predominates. Scanning electron microscopy and energy dispersive X-ray spectroscopy results are consistent with the abovementioned kinetic data.

On a utilisé du chlorate de sodium comme oxydant pour le lessivage de la chalcopyrite dans une solution d’acide chlorhydrique. La concentration de l’acide chlorhydrique a un effet important sur la dissolution de la chalcopyrite. Les résultats indiquent que la vitesse d’agitation a un effet négligeable sur la dissolution du cuivre, suggérant que la réaction ne serait pas contrôlée par la diffusion en phase liquide. Le lessivage de la chalcopyrite est également affecté par la température. Des études de diffraction des rayons X ont montré que le sulfure était oxydé en sulfate à des températures égales à ou à moins de 65°C, et à 85°C, il était oxydé en soufre élémentaire lors du procédé de lessivage. Les études de l’effet de la température sur la dissolution indiquent que le procédé de lessivage est hautement dépendant de la température dans la gamme de 25 à 65°C. Ce résultat est compatible avec les valeurs de l’énergie d’activation à 25–45°C (60·0 kJ mol^?1) et à 45–65°C (57·7 kJ mol^?1). Dans ces gammes de température, le procédé de lessivage est contrôlé par une réaction chimique. Cependant, à des températures de 65 à 85°C l’énergie d’activation au début (0–180 min) est de 28·17 kJ mol^?1, ce qui suggère que la réaction est contrôlée par diffusion et chimiquement lors de cette étape. Lors de la dernière étape (180–300 min) du procédé à 65–85°C, l’énergie d’activation est seulement de 0·55 kJ mol^?1. À ce point, il semble que la diffusion domine. Les résultats de microscopie électronique à balayage et de spectroscopie à dispersion d’énergie sont compatibles avec les données cinétiques mentionnées ci-haut.     

Activated sulfating roasting of the chalcopyrite concentrate for sulfuric-acid leaching

The sulfating roasting of the chalcopyrite concentrate with various pyrite contents is investigated in activated conditions in order to obtain the preferentially sulfate cinder most suitable for leaching and for the effective recovery of copper and accompanying iron. The activating effect that the trivalent iron sulfate which forms as a result of the low-temperature oxidation of pyrite, as well as the steam-air medium, has on the kinetics and completeness of the sulfatization of the concentrate are shown.     

Passive and transpassive anodic behavior of chalcopyrite in acid solutions

The electrochemical oxidation of CuFeS₂ in various acid solutions was studied using electrodes made from massive samples. The primary techniques employed were potentiodynamic polarization and constant potential experiments supplemented by capacitance measurements. It was the purpose of this study to investigate the behavior of: (1) several sources of CuFeS₂ in H₂SO₄ electrolytes, and (2) a single source of CuFeS₂ in various dilute acids. Electrochemical characterization of CuFeS₂ from various locations was performed in 1 M H₂SO₄ which showed significant differences in their behavior. All samples exhibited passive-like response during anodic polarization. The current density in this passive region was reproducible and showed differences of up to two orders of magnitude between samples from different sources which has been attributed mainly to the presence of impurities in some of the samples. During anodic polarization CuFeS₂ was found to be sensitive to pH at higher potential, but insensitive at low potential in sulfate solution. In addition, current decay measurements at constant potential in the low potential-passive region were found to follow the Sato-Cohen (logarithmic) model for solid film formation. Based on current and mass balance measurements, two intermediate sulfide phases appeared to form in the sequence CuFeS₂→S₁→S₂. At higher potentials, in the transpassive region, the observed increase in current is compatible with the decomposition of water to form chemisorbed oxygen which releases copper and forms sulfate ions.