The Influence of Anode Composition on Energy Consumption and Current Efficiency in Zinc Electrowinning

The basic method for the electrolytic zinc production is an electrowinning process based on sulfate solutions. The major problems for this industry are low current efficiency and high energy consumption leading to deterioration in the quality of cathodic zinc. The most applied approach for overcoming the mentioned problems is altering the zinc electrowinning conditions. Using Taguchi orthogonal (L25) array, five parameters (anode type, current density, sulfuric acid concentration, electrolyte temperature, and zinc concentration in electrolyte) at five different levels were selected to design and minimize the number of experiments. The experimental conditions were, zinc concentration of 50-80 g/L, acid concentration of 150-180 g/L, current density 500-1000 A/m2 and five different anodes at 30-60°C. Cast anodes of varying compositions that analyzed were Pb-Ag 0.5%, Pb-Ag 2%, Pb-Ag 0.5%-Sn 2%-Ca 1%, Pb-Ag 0.5%-Sn 2%-Bi 1%, and Pb-Ag 0.5%-Sn 2%-Sb 1%. The optimum conditions for the electrowinning process were anode composition: Pb-Ag 0.5%-Sn 2%-Sb 1%, current density: 500 A/m2, acid concentration: 165 g/L, electrolyte temperature: 50°C and Zn concentration: 80 g/L. Analysis of variance (ANOVA) showed that current density was the most important parameter. A smooth and compact structure in zinc deposits was obtained by using anode Pb-Ag 0.5%-Sn 2%-Sb 1%.