The effects of saponin,antimony and glue on zinc electrowinning from Kidd Creek electrolyte

The effects of Saponin alone and in combination with antimony and glue on zinc deposition current efficiency and polarization and on the morphology and orientation of 6h and 24h zinc deposits electrowon at 500 A m^–2 and 38°C from Kidd Creek zinc electrolyte were determined. Saponin, at concentrations to 100mgl^–1, was weakly polarizing, changed the preferred deposit orientation from basal to intermediate and decreased the current efficiency. At optimum glue + antimony levels, Saponin concentrations 5mgl^–1 resulted in an increase in zinc deposition current efficiency and consistently gave either a <114><112><103><102><101> or a <101><112> preferred deposit orientation depending on the antimony + glue combination used. Tests run for 24h for selected combinations of Saponin, antimony and glue confirmed the results obtained for the 6h studies.     

The effects of Dowfroth,antimony and Saponin on zinc electrowinning from Kidd Creek electrolyte

The effects of Dowfroth alone and in combination with antimony and Saponin on zinc deposition current efficiency and polarization and on the morphology and orientation of 6h and 24h zinc deposits electrowon at 500 Am^–2 and 38°C from Kidd Creek zinc electrolyte were determined. Dowfroth, at concentrations as low as 7 mg dm^–3, was strongly polarizing, changed the preferred deposit orientation from basal to intermediate and decreased the current efficiency and zinc deposit quality. Dowfroth had a positive interaction with antimony such that certain combinations of these reagents maximized current efficiency and improved the deposit quality. Saponin combined with various concentrations of Dowfroth resulted in a <1% change in current efficiency and did not modify the preferred deposit orientation. At optimum Dowfroth + antimony combinations, the addition of Saponin again did not affect significantly the current efficiency. The preferred deposit orientation was either [1 0 1][1 1 2] or [1 0 1] depending on the combination of these reagents employed. Tests run for 24h for selected combinations of Dowfroth, antimony and Saponin confirmed the results obtained for the 6h studies.     

The effects of nickel and cobalt and their interaction with antimony on zinc electrowinning from industrial acid sulphate electrolyte

The effects of nickel and cobalt and their interaction with antimony on the electrowinning of zinc from industrial acid sulphate electrolyte were studied using X-ray diffraction, scanning electron microscopy and cyclic voltammetry. Concentrations of cobalt as high as 20 mgl^–1 had no effect on the zinc deposition current efficiency. The current efficiency decreased rapidly when the electrolyte contained >5 mgl^–1 nickel. Neither cobalt or nickel had an effect on the morphology of the 1-h zinc deposits. Nickel and cobalt caused characteristic changes in the cyclic voltammograms for zinc deposition. As a result this technique might provide a rapid means for evaluating the electrolyte prior to zinc electrowinning. The combined presence of cobalt and antimony in the zinc electrolyte was more deleterious to zinc electrowinning than was the combined presence of nickel and antimony. The presence of 0.08 mgl^–1 antimony in the electrolyte counteracted the effect of nickel both on the current efficiency for 1-h deposits and on the zinc deposition polarization curves.     

Aluminium cathode effects in zinc electrowinning from industrial acid sulphate electrolyte

The effects of aluminum cathode grain size and surface conditioning treatments on zinc electrodeposition from purified industrial acid sulphate electrolyte were investigated. The Al cathode grain size had no effect on the long-time (15–60 min) deposit characteristics although deposits obtained using large-grain Al cathodes were often easier to strip. A study of the initial zinc nucleation (5–80s) showed that fine-grain Al cathodes had more zinc nucleation sites than largegrain cathodes. The influence of cathode preconditioning and glue on the initial zinc nucleation were also determined.     

Characterization of impurity effects in zinc electrowinning from industrial acid sulphate electrolyte

The individual effects of 15 impurities and their interaction with glue on zinc electrowinning from industrial acid sulphate electrolyte were characterized in terms of deposit morphology and preferred deposit orientation and in terms of current efficiency and zinc deposition polarization behaviour. The current efficiency decreased in a cyclical manner with increasing atomic number of the impurity element in each period of the periodic table. This decrease in current efficiency can be correlated to a corresponding increase in the rate of hydrogen evolution on the impurity metal. The various impurities produced four distinct zinc deposit morphologies and orientations and also produced characteristic changes in the cyclic voltammograms for the zinc deposition.     

On the effects of antimony and glue on zinc electrocrystallization behaviour

An investigation has been made to determine the effects that additions of glue and antimony have on the electrowinning of zinc from acid sulphate solutions. In particular, the zinc crystal growth and cathode current efficiencies were studied in an attempt to establish a correlation between morphology and the nature of the additives. Operating conditions of 55 A ft^–2#x002A; and 35°C were used for most of the experiments with electrolyte concentrations of approximately 55 gl^–1 zinc and 150 gl^–1 H₂SO₄. Additional runs were made at 40,75 and 100 Aft^–2 at 30,40 and 50°C in order to verify certain trends. Primarily by means of scanning electron microscopy (SEM) techniques, it was possible to categorize deposit morphologies according to the type and concentration of the additives. The general effect of antimony was to refine the grain size and cause the basal plane platelets to lie parallel to the substrate. Glue also caused some refinement, but caused the platelets to become aligned perpendicular to the substrate. Level deposits were obtained in the latter case, which would effectively prevent dendritic growths. A relationship between the relative amounts of glue and antimony in solution and the current efficiency was also obtained.     

The effect of copper on zinc electrowinning from industrial acid sulphate electrolyte

The effect of copper on the electrowinning of zinc from industrial acid sulphate electrolyte was studied using X-ray diffraction, scanning electron microscopy and cyclic voltammetry techniques. Concentrations of copper as high as 50 mg 1^–1 had no effect on the zinc deposition current efficiency for 1-h deposits. Copper co-deposited with zinc and reduced the deposit grain size. The copper content of the zinc deposits increased with increasing copper concentration in the electrolyte and with decreasing current density. The cyclic voltammogram for copper-containing electrolyte was characterized by an appreciable cathodic current in the reverse scan after zinc dissolution indicating the presence of previously deposited copper on the cathode.     

The effect of germanium on zinc electrowinning from industrial acid sulphate electrolyte

The effect ofgermanium on the electrowinning of zinc from industrial acid sulphate electrolyte was studied using X-ray diffraction, scanning electron microscopy and cyclic voltammetry techniques. Germanium concentrations > 0.1 mgl^–1 results in severe re-solution of the zinc deposit and hence decreased the zinc deposition current efficiency. Extreme fluctuations in the current efficiency occurred as a function of electrolysis time. Cyclic voltammograms obtained for Ge-containing electrolytes were characterized by a shoulder in the reverse scan prior to the cross-over potential. Vigorous hydrogen gassing occurred at the shoulder. These results are interpreted in terms of the formation of local Zn-Ge galvanic cells. Germanium concentrations to 0.2 mgl^–1 had no effect on the morphology of the 1-h zinc deposits but the preferred orientation changed from [1 1 4] [1 1 2] for Ge-free electrolyte to [1 1 2] [1 1 0] for electrolytes containing Ge.     

The effect of thiourea on zinc electrowinning from industrial acid sulphate electrolyte

The effect of thiourea, with and without glue and antimony additions, on the current efficiency (CE) and polarization behaviour of zinc deposition and on the morphology and preferred orientation of the zinc deposits electrowon (at 430 A m^–2 and 35°C) from industrial acid sulphate electrolyte (55 g l^–1 Zn and 150 g l^–1 H₂SO₄) has been determined. Increasing concentrations of thiourea in the electrolyte decreased the CE for zinc deposition; the additional presence of antimony did not significantly alter the decrease in CE but the presence of glue resulted in a further substantial decrease in CE. Thiourea changed the zinc deposit morphology and orientation, and also altered the shape of the zinc deposition cyclic voltammogram.     

The effect of tin on zinc electrowinning from industrial acid sulphate electrolyte

The effect of tin on the electrowinning of zinc from industrial acid sulphate electrolyte was studied using cyclic voltammetry, X-ray diffraction and scanning electron microscopy techniques. Tin concentrations < 2 mg l^–1 resulted in a rapid decrease in the current efficiency for l-h zinc deposits electrowon at 430 A m^–2; for tin concentration > 2 mg l^–1, the current efficiency remained constant at about 75%. The presence of tin in the electrolyte depolarized the zinc deposition reaction and resulted in a zinc deposit having a preferred [002] orientation. The addition of glue appeared to aggravate rather than counteract the adverse effects of tin.     

The role of zinc and sulfuric acid concentrations on zinc electrowinning from industrial sulfate based electrolyte

The effects of varying simultaneously the zinc/acid concentrations at a fixed total sulfate, on the current efficiency, energy requirements, and deposit physical characteristics for the zinc electrowinning, using Kidd Creek zinc electrolyte, were investigated. The electrowinning experiments were conducted using a laboratory scale apparatus, at plating cycles of 24 and 30 h, a current density of 500 A m^–2 and a temperature of 38 °C. These conditions are typical of those applied at the Kidd Creek zinc tankhouse. The reagents presently used at Kidd Creek, namely strontium carbonate, Saponin, Dowfroth 250, antimony and sodium silicate, were also continuously added to the cell electrolyte at levels similar to Kidd Creek practice. Scanning electron microscopy and X-ray diffraction techniques were used to characterize the deposits with respect to morphology and preferred orientation, respectively. Cyclic voltammetry was used to study the effect of the zinc/acid concentrations on the polarization behaviour of the electrolyte. In addition, the electrical conductivity of the Kidd Creek zinc electrolyte was measured and compared with other industrial sulfate-based zinc electrolytes.     

Effect of chromate ion on zinc electrowinning from acid sulphate electrolyte

The effect of chromate ion and its interaction with antimony and glue on zinc electrowinning from acid sulphate electrolyte were studied. During electrolysis at 430 A m^–2 and 45°C, the chromate ion was found to polarize the cathodic reaction resulting in a refined zinc deposit having a morphology featuring a vertical orientation of the zinc platelets. Although chromium did not codeposit, the current efficiency for zinc deposition was dramatically decreased in the presence of > 1000 mg dm^–3. This effect became more pronounced when the electrolyte also contained additives such as antimony and glue.     

Effects of 2-picoline on zinc electrowinning from acidic sulfate electrolyte

The behaviour of 2-picoline with and without antimony during electrowinning of zinc from acidic sulfate solutions was studied and was compared with that of gum arabic which is commonly used in industry as a levelling agent. The effects of these additives on current efficiency, power consumption, deposit quality, polarization behaviour, crystallographic orientation and surface morphology were determined. The addition of 2-picoline reduced current efficiency, increased power consumption and lowered the surface quality of electrowon zinc. Addition of antimony increased current efficiency, reduced power consumption and produced improved surface morphology and crystal orientations, (101) (112) (102) (103) (114) over a wide range of their combinations.     

The effects of As(III) and As(V) on zinc electrowinning from industrial acid sulphate electrolyte

The effects of As(III) and As(V), with and without glue and glue+antimony additions, on the current effeciency and polarization behaviour of zinc deposition and on the morphology and preferred orientation of 1-h zinc deposits electrowon from industrial acid sulphate electrolyte have been determined. As(III) had no effect on the current efficiency and did not alter significantly either the zinc deposition polarization curve or the zinc deposit morphology and orientation. Increasing concentrations of As(V) resulted in a significant decrease in the current efficiency for zinc deposition from addition-free electrolyte and from electrolytes containing added glue and glue+antimony. As(V) also changed the zinc deposit morphology and orientation, and significantly altered the shape of the zinc deposition cyclic voltammogram.     

The effects of 4-ethylpyridine and 2-cyanopyridine on zinc electrowinning from acidic sulfate solutions

The effects of 4-ethylpyridine and 2-cyanopyridine on the electrowinning of zinc in the presence and absence of antimony have been studied. The results are compared with those of a common industrial additive, gum arabic. Addition of either compound reduced current efficiency, increased power consumption and lowered the surface quality of electrodeposited zinc. Both the additives showed similar polarization behaviour to gum arabic. Addition of 0.04mgdm–3 antimony increased current efficiency, reduced power consumption and altered the surface morphology and crystallographic orientations. Combinations of antimony with 4-ethylpyridine resulted in very good current efficiencies, and zinc morphology and quality.     

The effects of metallic impurities and 2-butyne-1,4-diol on zinc electrowinning from chloride solutions

Zinc electrowinning tests from acidic chloride solutions showed that metallic impurities can be classified in the following order of detrimental effect on current efficiency: Sb>Co, Ni>Cu. This effect increased with higher HCl concentrations. Analysis of the impurity content of the zinc deposits showed the regular codeposition of Cu and the anomalous codeposition of Ni and Co.The use of 2-butyne-1,4-diol (0.86 g l^–1) was proven to be beneficial in the presence of Sb and particularly Ni. Both current efficiency and zinc deposit morphology were improved. The additive acted by selectively slowing the codeposition of the impurities with zinc.     

Scale-up effects in modelling a full-size zinc electrowinning cell

The scale-up of a mathematical model of a (10 dm³) pilot-plant zinc electrowinning cells is considered. All scale-up effects considered were relatively small in magnitude and their inclusion required only readily available full-size cell data. Excellent agreement was obtained between the model predictions and experimental results from an (instrumented) operational full-size cell.     

Effect of electrolyte characteristics on electrowinning of copper powder

This paper is concerned with studying the effect of electrolyte characteristics on the production process of electrolytic copper powder from partially depleted Cu containing synthetic electrolytes by electrowinning technique. The main electrolyte characteristics are temperature, circulation rate, Cu and H₂SO₄ concentrations, residence time in the cell, and utilization of organic bath additives. The process is positively affected by increasing the values of all of the studied parameters except for the addition of organic bath additives, which causes a negative effect. However addition of organic bath additives remarkably increases the degree of refinement of the produced powders. In most cases pure and fine copper powders were obtained with a dendritic shape, as indicated by scanning electron microscope (SEM) analysis.     

The effects of arsenic and lead impurities on the current efficiency and deposit composition in alkaline zinc electrowinning

The influence of lead and arsenic impurities on zinc deposition, current efficiency and deposit composition was examined in the alkaline zinc electrowinning system. It was observed that lead slightly decreases the current efficiency of zinc deposition, and that the detrimental effect on zinc current efficiency which was observed with arsenic was largely suppressed in the presence of lead. This beneficial effect is related to the fact that the arsenic content of the deposit decreased when lead was present in the electrolyte. It was also found that arsenic promotes the deposition of lead. Tin has no effect on the current efficiency of zinc deposition in alkaline solutions, with or without arsenic. The addition of salicylaldehyde to the solution alleviates the deleterious influence of arsenic on zinc current efficiency, but it somewhat increases the cell voltage.