Manganese removal from zinc sulfate electrolyte by electro-oxidation using Pb-Ag anode

ABSTRACT The optimum conditions for manganese dioxide (MnO2) removal were investigated in two simulated conditions, purification and electrowinning, using a Pb-0.7 wt.% Ag electrode. Linear sweep voltammetry and Cyclic voltammetry tests were conducted to study the effect of temperature and concentrations. SEM-EDS and XRD were employed to study the surface characterisations and chemical compositions. The results revealed that the electrowinning operating conditions are more appropriate than the purification conditions for MnO2 removal. The highest current efficiency of manganese removal was 21% which was obtained in the EW electrolyte at 125 A m−2 at 40°C after 2 h of electrolysis. The Current Efficiency was increased significantly at lower Mn ion concentrations (0.1–1.0 g L−1) while it stayed constant beyond the concentration of 1.0 g L−1. The results showed that an increase in temperature depolarised the oxygen evolution reaction and the addition of Mn2+ suppressed formation of PbO2 on anode surface.