The behavior of thiourea and flotation reagents in zinc electrowinning circuits

The effect of thiourea and flotation reagents on the electrowinning of zinc from industrial electrolytes was studied, and all the compounds were found to reduce the zinc deposition current efficiency and to change the properties of the zinc deposits. The effectiveness of activated carbon, two-stage cementation, and hot acid leaching on the destruction/removal of the organic compounds also was addressed. Activated carbon pretreatment of thiourea-containing electrolytes restored the current efficiency for 1-hour zinc deposits to values comparable to those obtained for thiourea-free electrolytes. The activated carbon pretreatment, however, altered the deposit morphology and orientation, but produced a cyclic voltammogram similar to that of the thiourea-free solution. Two-stage cementation did not counteract the harmful effects of thiourea. Hot acid leaching destroyed the thiourea but generated large concentrations of ferrous ion that reduced the current efficiency. The ferrous concentrations, however, were readily controlled by KMnO₄ or MnO₂ oxidation. None of the treatment options (activated carbon, two-stage cementation, or hot acid leaching) was effective in controlling the flotation reagents, and their moderately harmful effect on zinc electrowinning persisted. Even low concentrations of these reagents polarized zinc deposition, and this resulted in a “glue-type” zinc deposit.     

电解法制备树枝状锌粉工艺研究

对电解法制备树枝状锌粉工艺进行了研究,并采用激光粒度分析仪,扫描电镜对锌粉粒度分布及形貌进行分析,讨论了影响锌粉粒度大小、电流效率及其形貌的各个因素.结果表明:电解法制备的锌粉形貌为树枝状或鱼骨状;电解液中添加的硫酸铵对锌粉粒度影响不大;低Zn2浓度和高电流密度有利于获得粒度较小的锌粉.适当的刮锌粉间隔时间及添加剂对锌...     

Spouted bed electrowinning of zinc: Part I. Laboratory-scale electrowinning experiments

Two types of laboratory cells have been constructed to electrowin zinc from sulfate electrolytes: one cell was cylindrical while the other had a rectangular (flat) geometry. Cells were operated on industrial or synthetic electrolytes to electrodeposit zinc onto a spouted bed of zinc particles in the range of 0.75 to 1.45 mm. Current efficiencies and cell voltages have been measured during the course of batch experiments, enabling the calculation of the energy consumption per kilogram of zinc deposited. Electrolyte samples have been analyzed. Current densities (current per unit of cell cross-sectional area) were in the range of 1380 to 6200 A/m². Most catholytes were initially neutral and contained on the order of 150 g/L of zinc. Final acid contents were in the range of 39 to 114 g/L of sulfuric acid. The performance of the cells (particularly with respect to current efficiency) was superior to prior work on fluidized bed electrowinning from similar electrolytes. The flat cell was superior to the cylindrical cell and showed energy consumptions of less than 3 kWh/kg zinc at current densities up to 3500 A/m² when used to take the zinc content from 150 to 100 g/L zinc. Current efficiencies in this application ranged from 91 to 92 pct.     

The effects of certain impurities and their interactions on zinc electrowinning

The effects of germanium, antimony, arsenic, cobalt, glue, and free acid concentration were studied on both commercial and synthetic electrolytes. The effects of a single factor and the combined effects of multiple factors were elucidated. The temperature, zinc concentration, and current density were varied for some of the tests. It was found that the acid content was the most critical factor when impurity levels were at normal plant solution concentrations. The ranges where the effect of the impurity became apparent were: greater than 20 ppb (parts per billion) for antimony; 40 ppb for germanium; 120 ppb for arsenic; and 7 to 8 mg/1 for cobalt for a solution containing 65 g/1 zinc and 100 g/1 free sulfuric acid. At higher levels of acid, the acceptable level of impurity declined markedly. Glue additions were found to counteract the effects of antimony and germanium, but did little to counteract the effects of cobalt and arsenic. The level of acid was found to be especially critical when cobalt and arsenic were in the electrolyte. Cobalt and arsenic exhibited synergism, and lower current efficiencies were obtained for arsenic-cobalt combinations than expected. A factorially designed experiment was conducted to quantify the effects observed by one-factor-at-a-time testing. The structures and morphologies of the deposits were examined using X-ray diffraction and scanning electron microscopy.     

Fundamental studies on chlorine behavior as related to zinc electrowinning from aqueous chloride electrolytes

Measurements were made on the transport and equilibrium properties of dissolved chlorine in aqueous HC1, HCl-ZnCl₂, HCl-MgCl₂, and water. These measurements included solubility, absorption rates during bubbling, stripping rates during nitrogen bubbling, and cathodic reduction rates. The solubility of chlorine was found to be affected by speciation into aqueous Cl₂, HC1O, and C1₃ −. With increasing HCl concentration, the solubility of chlorine decreased to a minimum at 0.2 mol dm⁻³, followed by a slow and linear increase. Metal chloride salts depressed the chlorine solubility approximately in proportion to concentration. Mass transfer of aqueous chlorine was found to support a current of about 100 A m⁻² from a chlorine-saturated ZnCl₂-HCl solution under typical zinc electrowinning conditions. Comparisons with published zinc electrowinning papers indicate that air sparging would eliminate dissolved chlorine sufficiently to remove the need for diaphragm cell separation of dissolved chlorine, insofar as current inefficiencies due to cathodic chlorine reduction are concerned.     

锌电积节能措施的研究现状

传统的湿法炼锌过程中,存在着电积能耗大的问题．文章系统综合了当前锌电积的节电措施,并对新型惰性阳极材料及锌电积新工艺的研究现状进行了详细阐述．     

Evaluation of organic additives for use in zinc electrowinning

Organic additives are used extensively in zinc electrowinning to assist in controlling the process. A cyclic voltammetry technique has been developed to provide a rapid, quantitative evaluation of the effectiveness of selected organic additives in minimizing the deleterious effects that impurities, such as antimony, have on zinc deposition. Results have indicated that animal glues are more effective than the other organic additives tested, which included several gums, enzymes, and amino acids, in relation to the current efficiency of zinc production. Of the various animal glues compared in this research, the most effective appeared to have average molecular weights in the 25,000 to 30,000 range. The effects of certain process variables on the test results have also been evaluated; these included the acid concentration of the zinc sulfate solution and the cathode preparation.     

我国氧化锌矿浮选药剂研究进展

从捕收剂、抑制剂、活化剂、絮凝剂/分散剂等方面出发,总结了我国现阶段氧化锌矿浮选药剂的研究进展,强调了浮选药剂在氧化锌矿浮选过程中的重要作用,展望了氧化锌矿浮选药剂的发展趋势。     

白钨矿浮选药剂研究现状及展望

提高捕收剂的选择性和强化抑制剂的高效性始终是白钨矿浮选研究中的重点.从白钨矿的捕收剂和调整剂的种类、作用机理及研究使用现状等方面进行了分析,提出高选择性捕收剂和针对性强的抑制性是白钨矿浮选急需解决的问题.运用高新技术,结合理论研究,开发高效、经济、环保的浮选药剂已成为白钨浮选药剂的发展趋势.     

Evaluation of organic additives for use in zinc electrowinning

Organic additives are used extensively in zinc electrowinning to assist in controlling the process. A cyclic voltammetry technique has been developed to provide a rapid, quantitative evaluation of the effectiveness of selected organic additives in minimizing the deleterious effects that impurities, such as antimony, have on zinc deposition. Results have indicated that animal glues are more effective than the other organic additives tested, which included several gums, enzymes, and amino acids, in relation to the current efficiency of zinc production. Of the various animal glues compared in this research, the most effective appeared to have average molecular weights in the 25,000 to 30,000 range. The effects of certain process variables on the test results have also been evaluated; these included the acid concentration of the zinc sulfate solution and the cathode preparation.     

Fluidized bed electrowinning of zinc from chloride electrolytes

The fluidized bed electrowinning of zinc from chloride electrolytes has been studied in a laboratory cell. The cell was operated at superficial current densities in the range 1200–7500 A/m² with catholytes containing up to 62 kg/m³ Zn and up to 28 kg/m³ HCl. Anolytes examined contained 58 kg/m³ NaCl and up to 100 kg/m³ HCl and, in some instances, had the same composition as the catholyte. Both “pure” catholytes and ones with deliberate additions of impurities (Ni, Co and Sb) were used. Pure solutions yielded current efficiencies and power consumptions comparable to or better than those of cells with conventional electrodes. Antimony (particularly in combination with Ni and Co) had a detrimental effect on cell performance; this detrimental effect was largely alleviated by simultaneous additions of glue.     

The simultaneous electrowinning of manganese dioxide and zinc from purified neutral zinc sulphate at high current efficiencies

A process that enables electrolytic-grade manganese dioxide and zinc to be electrowon simultaneously at high anodic and cathodic current efficiencies from purified neutral leach liquor from a zinc plant is described. Experimental results that show the effects on the anodic and cathodic current efficiencies of temperature, anodic and cathodic current densities, initial sulphuric acid concentration, initial zinc-ion concentration, initial manganous-ion concentration, and addition of a polyelectrolyte smoothing agent are presented and discussed.     

Conductive polymer coating for anodes used in zinc electrowinning

Abstract

In this study polypyrrole was coated on the lead silver alloy (0·5 wt-%) using electrochemical synthesis. The performance of the coating on the lead alloy corrosion behaviour in a severe corrosive electrolyte has been evaluated. Also, the morphology of polypyrrole coating was studied utilising scanning electron microscopy (SEM). The results show that the protective layer of polypyrrole decreases the corrosion rate of the anodes by about 30% for the optimum coating condition.

Dans cette étude, on a recouvert l’alliage de plomb et argent (0·5% en poids) avec du polypyrrole en utilisant la synthèse électrochimique. On a évalué le rendement du revêtement sur le comportement à la corrosion de l’alliage de plomb dans l’électrolyte sévèrement corrosif. On a également étudié la morphologie du revêtement de polypyrrole en utilisant le microscopie électronique à balayage (SEM). Les résultats montrent que la couche protectrice de polypyrrole diminue la vitesse de corrosion des anodes par environ 30% en condition optimale du revêtement.     

锌电积节能措施的研究现状

传统的湿法炼锌过程中，存在着电积能耗大的问题。本文系统综合了当前锌电积的节电措施，并对新型情性阳极材料及锌电积新工艺的研究现状进行了详细阐述。     

金属杂质离子对长周期锌电积的影响

阐述了长周期锌电积过程中金属离子杂质对电流效率和电锌质量等方面的影响.     

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”.     

The anomalous behavior of Al3+ in nickel electrowinning from sulfate electrolytes

The effect of varying concentrations of Al³⁺ on the morphology and current efficiency of electrodeposited nickel from an acid-sulfate electrolyte was studied. Concentrations of Al³⁺ of 20 to 100 ppm significantly degraded the nickel-cathode morphology and current efficiency. However, it was found that higher concentrations of Al³⁺, in the range of 1 to 5 g/L, depending on the electrolyte parameters and operating conditions, improved the deposit morphology compared to deposition from a pure electrolyte. However, the current efficiency remained low. Physical characterization of the nickel revealed that a smoother, more uniform surface resulted from deposition in the presence of 1 g/L or greater of Al³⁺. Impedance analysis indicated the presence of an inhibiting layer on the cathode when low concentrations of Al³⁺ were present. Concentrations of Al³⁺ greater than 1 g/L appeared to modify this layer and the nickel-deposition mechanism, allowing improved nickel morphology and structure.     

Effects of additives on zinc electrowinning from industrial waste products

An investigation of the effects of some additives on zinc electrowinning from a weak acidic sulphate electrolyte prepared from an industrial waste product has been carried out. Experiments were done in the presence of additives such as aluminium sulphate, animal glue and an extract of horse-chestnut nuts (HCE), used alone or in different mixtures.Using a rotating disc electrode (RDE) and cyclic voltammetry, the influence of the additives on the polarization curves and on the voltammograms was studied. SEM was used to determine the structure and the morphology of deposits.The results indicated that the additives tested exert a beneficial effect on the quality of the zinc deposits. They increase the cathodic polarization and promote levelling. Al₂(SO₄)₃ influences the reduction of zinc ions, increasing the nucleation overpotential and the deposition rate of zinc on the cathode. The conjoint use of Al₂(SO₄)₃, animal glue and HCE results in smooth, slightly bright deposits, showing a beneficial effect of the mixture on zinc electrodeposition. The analysis of deposit purity suggested that the additives inhibit the discharge rate of impurity metal ions, such as copper and lead, whose deposition is diffusion controlled.     

锌电积大极板和自动化剥锌的应用实践

介绍了大极板技术的工艺条件和自动化剥锌设备的主要结构、运行过程,同时介绍了整个自动化系统的运行过程.总结了影响自动化剥锌的关键原因.     

The influence of nickel ions on the long period electrowinning of zinc from sulfate electrolytes

The effects of nickel ions on cathodic current efficiency, electrical power consumption, cell voltage and the surface morphology of deposits during the long period electrowinning of zinc from acid sulfate electrolytes are investigated in this paper. The polarization behavior of the cathode is also examined. The presence of nickel ions in the electrolytes increases the electrical power consumption, decreases the current efficiency, affects the cell voltage and produces the worse surface morphologies. The results of the experiments also show that the zinc electrodeposition process and the cathodic polarization behavior are greatly changed in the presence of nickel ions in the electrolytes.