Anodic dissolution of copper sulphides in sulphuric acid solution: II. The anodic decomposition of CuS

The anodic decomposition of CuS in sulphuric acid solutions was investigated by means of cyclic voltammetry. The pH of the electrolyte and the scan rate were varied. Our results are interpreted using the experience of semiconductor electrochemistry and of passivation of pure metals. At potentials E < E_np (E_np = potential of pitting nucleation), the current/voltage curves were interpreted by the formation of metastable nonstoichiometric copper oxide or hydroxide. After the dissolution of these layers at the potential E_np, total decomposition of CuS starts. These results were confirmed by rest potential measurements and by scanning electron microscopy.     

Anodic dissolution of copper sulphides in sulphuric acid solution: I. The anodic decomposition of Cu2−xS

The anodic dissolution of Cu_2?xS in sulphuric acid solution was investigated by means of cyclic voltammetry. The results obtained may be interpreted by a combination of several concurrent reactions: solid state reaction and diffusion through an anodic-formed CuSO product layer. diffusion in the pores of the product product layer and - in concentrated CuSO₄ solutions - resistance polarization in the pores of the CuSO₄ precipitation. The formation of thin metastable oxide films may also control the current density.     

Studies on the anodic dissolution of copper matte

Anodic polarisation studies on copper matte revealed that a copper matte electrode polariess abruptly in H,SO, solution but not in HCl solution. Anodic dissolution of copper matte was studied at various anodic potentials in 2 N solutions of HCl and H,SO,. It was found that at lower anodic potential (around 0.4 volt vs. saturated calomel electrode) copper dissolves preferentially (at 90% current efficiency) over iron (8–10% C.E.), in both the acid solutions. It was further observed that this preferential dissolution of copper takes place over a longer period (about 6 h) in HCl than in H₂SO₄ solution (about 3 h). Preferential dissolution of copper from copper matte was found to be independent of HCl concentration (0.5 N to 4 N). From the X-ray diffraction analysis of the original copper matte and electrolysed copper matte, it was established that digenite and bornite phases of copper matte dissolved causing preferential dissolution of copper.     

New observations on the anodic oxidation of copper in hot acidified copper sulfate solutions

The anodic oxidation of copper in acidified copper sulfate solution has been investigated by potentiostatic and voltammetric techniques. The morphology and composition of the films were determined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The passive layer is mainly composed of CuSO₄. The presence of a Cu₂O phase becomes detectable after multiple sweeps and thorough rinsing of the electrode with water at the end of the experiment. The effects of electrolyte composition and temperature on the phenomenon of passivation are also discussed. The initial steps of the copper dissolution were found to obey Tafel kinetics, and the maximum dissolution current, as well as the limiting transpassive current, was controlled by the rate of diffusion of cupric ions. The phenomenon of current oscillations occurs at potentials near the peak current upon scan reversal, suggesting that oscillations only occur with the formation of a sufficiently thick film. Oscillatory behavior disappears when conditions favor salt film stability. Formerly with the Departement de Mines et Métallurgie, Université Laval. MAGDY GIRGIS, formerly with the Department of Chemistry, Carleton University.     

Cuprous hydrometallurgy Part IV. Rates and equilibria in the reaction of copper sulphides with copper(II) sulphate in aqueous acetonitrile

Copper(II) sulphate in solutions of aqueous acetonitrile leaches copper from copper sulphides to form stable copper(I) sulphate solutions. Covellite and chalcopyrite are oxidised and leached more rapidly in the early stages of leaching with acidic CuSO₄/CH₃CN/H₂O than with acidic iron(III) sulphate in water. A redox equilibrium between copper(I) sulphate, copper(II) sulphate and partially leached solid copper sulphide, Cu_xS, is established. The equilibrium concentration of Cu₂SO₄ and the value of x in Cu_xS, in solutions saturated with CuSO₄, are interdependent if the acetonitrile concentration is constant. This behaviour is considered in terms of the structural and electrochemical changes which occur, in the solids Cu₂S and CuS, as leaching proceeds. According to the activities of acetonitrile, of copper(I) sulphate and of copper(II) sulphate, i.e. according to the redox potential of the solution, CuS either can be oxidised by copper(II) sulphate to a less copper-rich copper sulphide and even to sulphur, or reduced by copper(I) sulphate to a more copper-rich sulphide, up to Cu₂S, in acidic solutions containing CuSO₄, Cu₂SO₄, CH₃CN and water. This observation leads to an easy method of generating Cu₂S from CuS or from sulphur.     

The effect of preferential flow on extraction and surface morphology of copper sulphides during heap leaching

Despite the commercial achievement of heap leaching of some copper, gold, zinc, and nickel minerals, there is limited comprehension of the flow pattern within the heap. Several field investigations have suggested that bypassing of ore by leaching solution is a common phenomenon, and the leaching process was significantly influenced by it. The extraction and surface morphology of low-grade copper sulphides under the condition of preferential flow was investigated in this paper. The experiment result, conducted within a novel bioleaching apparatus, shown that majority of acid was consumed by alkaline gangue and matrix, so the concentration of Cu²⁺ and total Fe increased slightly at the initial leaching stage. The ore extraction decreased with the increasing of its location depth, for instance, the ore extractions of the top and bottom region were 29% and 2% respectively. Preferential flow happened within the fine region due to the low irrigation employed by this experiment, and the extraction of fine ores was larger than that of coarse ores. The SEM images showed that the surface of top ores within the column was degraded seriously, but the middle and bottom ores were attacked slightly. Plenty of cracks were observed on the bottom ore surface due to the precipitation layer of sulfur and jarosite.     

铜矿山地质勘测技术应用分析

当前,铜矿资源开发的地质环境日益繁杂,缺少相应的技术支持,对铜矿资源的有效开发影响巨大。基于此,本文就铜矿山地质勘测技术的应用进行深入地探讨。     

Electrochemical interfacial phenomena under microgravity: Part 2. Numerical analysis of the rate of ionic mass transfer accompanying anodic copper dissolution

The anodic dissolution phenomena of copper, under microgravity in a drop shaft, was compared to that in terrestrial experiments. A 0.1 M CuSO₄-1 M H₂SO₄ solution layer was confined to a shallow (200-μm-thick) and horizontally installed electrolytic cell. Relatively higher constant current densities were applied for visualization within 8 seconds of electrolysis duration. Fluid flows were induced in the decelerated zone of the drop shaft and in the terrestrial experiment. The interference-fringe pattern, which accompanied the copper dissolution, was measured in situ with a common path-type microscopic interferometer. Numerical analysis was used to compare the development of the interference-fringe pattern in both environments. Two boundary conditions at the anode surface were employed: a constant current density with any degree of supersaturation and a solubility limit at the surface. The calculated surface concentration was used to discuss the transient variation of measured anode overpotential. A larger degree of supersaturation, before the anodic overpotential started to increase, which was probably caused by CuSO₄ precipitates followed by a kind of passivation film formation, was calculated under a microgravity environment. The drop-shaft facility provides a good opportunity to study the electrochemical interfacial phenomena which are necessary to precisely design the micromachining or microfabrication processing.     

Sintering of copper powder subjected to cryomechanical treatment

Translated from Poroshkovaya Metallurgiya, No. 2(326), pp. 18–23, February, 1990.     

阳极溶出伏安法同时测定锌电解液中镉铜钴

采用阳极溶出伏安法,建立了在pH 5.0的HAc-NaAc缓冲溶液中,NH4Cl溶液为支持电解质和辅助络合剂,使离子溶出峰电位差增大、峰形尖锐并消除锌离子的影响,抗坏血酸为除氧剂消除氧波干扰的检测体系,可不经预分离直接测定锌电解液中镉(Ⅱ)、铜(Ⅱ) 、钴(Ⅱ)三种金属离子。实验结果表明：在该体系中镉(Ⅱ)、铜(Ⅱ)、钴(Ⅱ)的溶出峰电位分别在-0.82、-0.22、+0.02 V;校准曲线的线性范围分别在6×10^-7~2.5×10^-5, 3×10^-7~3×10^-5,1.5×10^-6~3.0×10^-4 mol/L;方法的检出限分别是3×10^-8,2×10^-7和1×10^-8 mol/L。电解液中可能存在的常见离子对测定无影响。方法用于实际样品的测定,其结果与ICP-AES方法的测定结果一致。     

Thermodynamic analysis on the role of hydrogen in anodic stress corrosion cracking

A synergistic effect of hydrogen and stress on a corrosion rate was analyzed with thermodynamics. The results showed that an interaction of stress and hydrogen could increase the corrosion rate remarkably. Stress corrosion cracking (SCC) of austenitic stainless steel (ASS) was investigated in boiling chloride solution to confirm the analysis. Hydrogen could be introduced into the specimen and concentrated at the crack tip during SCC in boiling LiCl solution (143°C). The concentrating factor is about 3 which is consistent with calculated results according to stress induced diffusion.     

Examination of the United Nations self-heating test for sulphides

Some materials when exposed to various conditions can exhibit a rise in temperature without requiring an external heat source. Generally referred to as pyrophoric or self-heating substances, they challenge the safety of materials handling, storage and transportation. Reliably assessing the self-heating potential of materials is thus essential. Over the years several test protocols have been developed. A widely accepted method is that recommended by the United Nations (UN) to certify the safety of shipping pyrophoric goods. Our test work on sulphide materials has shown that the UN test can give false negatives if the sample oxidation history is not considered. Depending on the degree of oxidation (‘weathering’), the same sulphide material can exhibit self-heating ranging from safe to hazardous. To make the UN test, and other single-stage self-heating procedures, more reliable in assessing self-heating potential of sulphide materials, it is recommended that a weathering step be incorporated in the test protocol. Our test work on two sulphide samples, an ore and a concentrate, demonstrates the impact of incorporating a weathering stage in the test protocol.     

An analysis of stress corrosion crack growth by anodic dissolution

An analysis of the distribution of electrode potential within a stress corrosion crack which is growing by an anodic dissolution process has been used to define the electrode potential at the tip of the crack. This potential is used to predict the kinetics of crack growth. The influence of the applied stress intensity and the electrochemical properties of the crack tip and surface on the growth rate have been considered for low alloy steels in concentrated hydroxide solution and aluminum alloys in acidic chloride solution. Crack growth rates obtained in high concentration solutions are extrapolated to lower concentration solutions which may be expected in service environments. Predicted crack growth rates are in good agreement with published data.     

样品表面化学抛光处理法应用于薄板钢中氧的分析

研究了不同的样品表面处理方法对测定薄板钢样中氧的影响。经试验,确认采用由磷酸、醋酸和硝酸组成的化学抛光液可将薄板表面的涂层和氧化层处理干净。运用正交试验法对化学抛光处理薄板的温度、时间和试样重量3个因素进行了优化,并对影响分析结果准确度的因素进行了探讨,最终确定了因素的最佳水平,即浸泡时间:2min,温度:70℃,样重:0.4～0.5g。实验证明,化学抛光比机械抛光简单易行,经化学抛光液处理的试样对氮的测定结果无影响,可进行氧氮联测,测定薄板中氧和氮的结果相对标准偏差小于4.4%,能满足实际生产中的检测要求。     

等效24脉波整流机组在铜电解中的应用与分析

本文针对整流机组在铜电解中的应用,详细论述了等效24脉波整流机组的工作原理,提出采用等效24脉波整流机组作为电解电源,与其它铜电解整流机组方案相比,具有更高的可靠性和稳定性。     

张力辊表面处理工艺的应用分析

为提高张力辊辊面性能,分别采用在辊面电镀硬铬、HVOF喷涂WC-12Co、HVAF喷涂WC-12Co三种工艺对张力辊辊面进行强化处理,并对随辊试样进行分析。发现镀铬层内部存在一定的微裂纹,硬度达到900HV_0.3;HVOF制备的涂层孔隙率为2.3%,涂层硬度1 100HV_0.3;HVAF制备的涂层孔隙率为0.6%,涂层硬度1 400HV_0.3;三种工艺制备的最终辊面粗糙度Ra均能满足上机使用要求,镀铬辊使用6个月后,辊面粗糙度下降严重,而WC涂层辊面的粗糙度保持相对稳定。     

碳纳米管修饰碳黑微电极阳极溶出伏安法测定痕量铜

制备了多壁碳纳米管修饰碳黑微电极并研究了铜在该电极上的阳极溶出伏安行为;在极谱分析仪上采用二阶导数线性扫描伏安法进行分析,提出了一种测定痕量铜的新方法。实验发现,在0.1 mol/L HAc-NaAc缓冲液(pH 4.2)中,铜离子于-400 mV(vs.SCE)处被吸附还原,富集在该修饰电极表面。从-400 mV以100 mV/s的速率正向扫描至400 mV,铜在约-22 mV处出现一灵敏的阳极溶出峰。峰电流与铜的浓度在8.0×10-10~1.0×10-7mol/L范围内呈良好的线性关系,检出限(S/N     

CENTUM CS1000在贵冶炼铜倾动炉的应用

在开放型CENTUM CS1000的基础上，设计了针对贵冶炼铜倾动炉的控制系统．一年多的运行结果表明。此设计是完全成功的．