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

Abstract

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.