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

Abstract

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.