Material balance and current efficiency in electrowinning

A process variable in addition to the current efficiency is required in order to obtain exact correlation among current, electrolyte flow, and concentration changes in electrowinning. To this end, a volume efficiency has been defined and incorporated into a formulation for estimating the separate contributions to observed current efficiencies.In Part I, expressions are presented which enable the response of the electrowinning system to changes in influent to be accurately predicted. The formulation developed is practical, and its use is illustrated by actual examples. Part II presents a somewhat idealized treatment, in that very precise and accurate chemical analyses would be required in order to obtain a reliable estimation of the relative rates of competing electrode reactions.     

金隆铜电解精炼生产实践

介绍金隆铜业有限公司近几年铜电解精炼的生产状况,分析高杂质电解条件下阴极铜出现质量波动的原因和采取的解决措施、电积脱杂方面的改造和效果、萃取法脱除锑铋在电解液净化方面的应用、降低阴极铜含银的措施方法等。     

Physico-chemical properties of copper electrorefining and electrowinning electrolytes

Densities, viscosities, electrical conductivities and specific heats of solutions containing copper, nickel, arsenic, iron and sulphuric acid in the concentration ranges of copper electrorefining and electrowinning electrolytes have been measured. Equations are presented for calculating these properties as a function of electrolyte composition and temperature. DEREK C. PRICE, formerly Research Associate, Department of Mining and Metallurgical Engineering, McGill University, Montreal, Canada     

The fluidized bed electrowinning of silver

Fluidized bed electrowinning appears to be an alternative to the Zadra cell usually employed to deposit silver electrolytically from cyanide solutions. By using a bench scale cell it was found that when using either pure silver or silver coated copper particles such electrowinning could be carried out without operating problems and with reasonable current efficiency and cell voltage. Various anodes, for use in the cell, were examined and three found to be satisfactory. By electrolyte analysis and by EDAX analysis of the silver deposit, the silver was shown to be free of impurities down to the detection level of the analyses.     

Study of electrical conductivity for electrolytes of electrowinning and electrorefining processes

Although a number of studies have been reported on the electrical conductivities of sulphate electrolytes for electrowinning and electrorefining processes, very few have focused on the optimization of these different effective factors. In this study, a design of experiment (DOE) technique, the Taguchi method, has been used to optimize four main effective factors (temperature of electrolyte, sulphuric acid concentration, metal ion concentration, impurity concentration) on electrical conductivity of sulphate solutions. The percentage contributions of these effective factors and their ranking have been revealed. Sulphuric acid concentration is the main effective factor on electrical conductivity of electrolyte while the temperature of electrolyte is in the second important factor. The article is published in the original.     

A Mineralogical overview of the behavior of nickel during copper electrorefining

Nickel-bearing copper anodes and anode slimes were studied using a variety of mineralogical and chemical techniques. In anodes containing <;0.3 pct Ni, the nickel occurs only in solid solution in the copper matrix. This nickel dissolves simultaneously with the copper during electrorefining, but a small amount reprecipitates as copper-nickel sulfate or a complex Ni-bearing Cu-Ag-As-Se-S oxidate phase in the anode slimes. In anodes containing >0.3 pct Ni, NiO crystals also form. The presence of the Cu-Ni-Sb oxide, kupferglimmer, in the anode depends on its antimony content. Kupferglimmer is prevalent in nickel-rich anodes with high Sb contents (>200 ppm) but is not found in similar anodes with Sb contents <200 ppm. Various Cu-Ni and Ca-Cu-Ni silicate inclusions are present. Depending on the iron content of the anode, Fe-bearing NiO, NiFe₂O₄, and other Ni-bearing iron oxide phases also may be present. All of the oxidate nickel phases remain largely undissolved during electrorefining and concentrate in the anode slimes.     

制备活性镍扣的工艺研究及问题探讨

介绍了采用氯化介质不溶阳极电解工艺制备镍扣的工艺流程及技术条件。论述了镍扣研制试验中气孔产生的原因及预防措施，对添加剂ＳＮ 的作用、主要影响因素及控制作了较详细的阐述。     

镍电解工艺条件对杂质铅、锌、硒阴极析出行为的影响

采用循环伏安法研究镍电解液中杂质铅、锌、硫、硒在镍电解精炼中的电化学行为。结果表明,铅、锌在阴极还原为金属单质,硫、硒则与镍离子生成Ni_xS_y及Ni_xSe_y。采用阴极极化法研究了电解工艺条件即温度、pH、氯离子浓度对杂质铅、锌、硫、硒的还原电势的影响。在工业生产中可根据杂质控制的需要来调整电解条件,从而减少部分杂质元素在阴极析出的总量。     

Processes during the electrorefining and electrowinning of lead

The anodic and cathodic processes in the fluorosilicate electrolytes during galvanostatic deposition under (DC) and polarity reversal current (PRC) regimes were investigated. It was established that, during the process of lead electrorefining from concentrated electrolyte without applying PRC, at c.d. i = 300 A/m² (3 A/dm²), after 60–80 h of the 95 h operation cycle, a limiting anodic polarization barrier value (Δ?_Acr = 200 mV) is attained. In this case bismuth and antimony start to dissolve actively from the anodes and are deposited onto the cathode, while under PRC conditions Δ?_Acr is not reached even after 95 h. The cathodic deposits are rounded crystal grains and display pronounced epitaxial growth. Spectral analysis shows that Sb is the main impurity of cathodic lead instead of Bi.During the electrowinning of the lead, without using H₃PO₄ as an inhibitor of β-PbO₂ parasitic deposition onto the inert graphite anodes, it was established that a critical value of the anodic potential ?_Acr = 1430–1500 mV/SCE) exists, under which β-PbO₂ is not deposited. If H₃PO₄ is present, β-PbO₂ is not deposited onto the graphite anodes at any values of the anodic potential.     

Fluid bed electrolysis of nickel

A laboratory scale cylindrical fluidized cathode cell is evaluated as a means for electrowinning nickel. Key parameters affecting nickel deposition are characterized: cathode current feeder design, flow distribution systems, anode configuration, temperature, current density, pH, nickel concentration, electrolyte conductivity, and electrolyte impurities. A study is made of anode/cathode separator membranes. Titanium, steel shot, graphite, sand, nickel shot, and nickel oxide are evaluated as bed materials.     

Addition of Cobalt to Lead Anodes Used for Oxygen Evolution—A Literature Review

A review of the literature dealing with the effect of cobalt on lead-based anodes for oxygen evolution during electrolysis of sulfuric acid solutions verifies that the presence of cobalt at the anode–electrolyte interface, either as constituent of the anode material or as ions in the electrolyte, catalyzes the evolution of oxygen and reduces the corrosion of the anodes and the contamination by lead of metal cathodes produced during electrowinning. However, due to harmful effects of cobalt ions on the cathodic reaction in some processes, these benefits are limited to the electrowinning of copper. Efforts to develop a way of introducing cobalt at the anode–electrolyte interface without interfering with the cathodic reactions are reviewed in this paper. The use of lead–cobalt alloy anodes has had limited success due to issues arising from the low solubility of cobalt in lead, segregation during casting of the alloys, and nonuniform distribution of cobalt which affects the integrity of the anodes. This has been overcome in part lately by inclusion of cobalt into only the surface layer of a lead or lead alloy substrate, by thermal treatment of a cobalt salt to form a catalytic cobalt oxide surface species, or by electrodeposition of composite lead–cobalt oxide anodes. The last approach in particular has been actively investigated by several groups, but to our knowledge it is yet to find application in the industry. The review also critically examines the likely reaction mechanisms involved.     

Influence of malonic acid and triethyl-benzylammonium chloride on Zn electrowinning in zinc electrolyte

The influence of malonic acid and other additives has been investigated during the electrowinning of zinc from acid sulphate solutions containing manganese ions. It was found that adding malonic acid “MA” increased the current efficiency and decreased the anodic and cathodic potentials and the cell voltage in the standard electrolyte. Adding malonic acid to the industrial electrolyte containing antimony impurity also led to an increase in the current efficiency. Triethyl-benzylammonium chloride “TEBACl” was the best additive to improve current efficiency with the presence of 5 mg/L Ni²⁺ impurity and it also counteracted the deleterious effect of Sb³⁺ better than the other additives such as polyethylene glycol, sodium lauryl sulphate, perfluoro-heptanoic acid and malonic acid—these were not as good as glue and chloride ion together. Adding 2 mg/L of “TEBACl” to sulphuric acid solution with the presence of nickel ions increased the cathodic potential of hydrogen evolution on the zinc deposit, much more than that of 100 mg/L “MA”.     

Electrowinning copper from solvent extraction acid strip solution using Pb-Sb anodes

Copper electrowinning from solvent extraction acid strip solutions was studied as a part of a more comprehensive laboratory investigation on development of a process for treating native copper ores by ammoniacal leaching-solvent extraction-electrowinning methods. Because initial electrowinning tests resulted in poor quality copper cathodes, a study was undertaken to determine the conditions necessary for producing high-quality electrowon copper before proceeding with other phases of the process development. The electrowinning tests showed that removing entrained organic from the electrolyte, maintaining a protective voltage on the anodes when electrowinning was not in progress, and adding a small amount of cobalt to the electrolyte resulted in production of copper cathodes with a low lead content when using antimonial lead anodes. After satisfying these conditions, large variations in other operating conditions were possible without materially affecting the lead content of the electrowon copper. Copper cathodes with lead contents of less than 2 ppm were consistently produced. These results were obtained with laboratory-scale equipment and quantitative extrapolation to industrial-scale operations may not be valid. However, the qualitative effects of the various processing conditions should be applicable to industrial electrowinning.     

Electrorefining zinc dross in ammoniacal ammonium chloride system

A zinc dross was cast into anodes and electrorefined in an ammoniacal ammonium chloride electrolyte (NH₃–NH₄Cl) to produce high purity zinc. The influence of several factors, such as zinc concentration, current density and temperature, on cathodic current efficiency and power consumption were investigated. The results indicated that increasing Zn concentration increased the current efficiency, but, very high Zn concentrations affected the progress of the electrolysis of zinc dross. The power consumption can be decreased effectively by increasing the temperature of electrolyte. High current density adversely affected the quality of the cathodes and increased the power consumption. The morphology of cathodic zinc can be improved by increasing Zn concentration at an appropriate current density and its purity was very acceptable. All the experimental results obtained showed a technical feasibility of the NH₃–NH₄Cl system as an electrolyte system for electrorefining of zinc dross.     

The effects of Mg2+, Mn2+, Zn2+, and Al3+ on the nickel deposit during electrowinning from sulfate bath

The presence of impurities like Mg²⁺, Mn²⁺, Zn²⁺, and Al³⁺ during electrowinning of nickel shows several effects. The effects include current efficiency, deposit quality, purity, crystallographic orientation, surface morphology, and polarization behavior. Addition of the impurities did not change the current efficiency significantly but did change the quality and purity of the electrodeposited nickel. Based on the quality of the deposits obtained, the tolerance limits of these impurities in nickel bath were obtained. Although no deviation of nickel structure from fee was observed, the peak height values for different orientations changed with all of the impurities and the values varied with impurity concentration. The surface morphologies of electrodeposited nickel in the presence of impurities also showed changes. The potentiodynamic scan curves for nickel deposition showed deviations in the presence of all the impurities studied. Based on the results, an attempt was made to correlate the various effects.     

锌电积用铅基阳极的研究现状及发展

从合金配伍和制造方法上阐述了锌电积用铅基合金阳极材料的研究现状,通过比较对未来锌电积用惰性阳极材料的发展趋势进行了展望,并提出降低阳极生产制造成本,关键在于降低阳极含银量,在于开发多元合金压延阳极板。     

铜电解电耗因素影响分析及研究

通过铜电解工艺理论分析、电解液物理特性试验、工业试验平台测试,研究了铜电解精炼过程电解液电导率对电耗的影响,确定了电解液温度、硫酸浓度、镍离子浓度与电耗的定量关系,根据现有电解液净化工艺流程,提出最佳镍离子浓度值。     

影响铟电解精炼电流效率因素的研究

论述了电流强度、电解通电时间、电解液成分、电解液循环速度、极距、槽电压等因素对铟电解精炼电流效率的影响,并提出了高电流效率下的电解工艺条件及其相应的控制方法,铟产品质量可达99.9993%,电流效率控制在88%左右。     

铜电积技术的发展现状及应用前景

介绍了现有商业铜电解技术最新进展及发展方向.过去的40年间,湿法炼铜工业经历了重大变革.目前,随着科技进步,高质量铅合金阳极、改良的不锈钢基板、先进的电解质控制和电解车间自动化技术的出现,电积铜技术越来越成熟.不久的将来,电积铜技术(包括尺寸稳定的阳极,替代的阳极反应,新颖的电解槽设计和创新的电解循环系统)将会有更低的生产成本,更高质量的产品,这将使电积铜产业有更大的发展.     

Transport and cathode deposition of reducible impurities during electrorefining with nonpolarizable electrodes

A general equation for cathode impurity concentration is developed for steady-state electrorefining with an impurity that is more readily reduced than the primary metal. The results depend on the equilibrium cathode/electrolyte distribution coefficient and the transport properties of the electrolyte. Applicability is restricted to situations where electrode kinetics are not rate limiting, such as most fused salt systems. Experimental results for copper impurity in a Sn/fused SnCl₂/Sn system are compared with calculated cathode impurities as a function of cell voltage.