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

Abstract

The optimum conditions for manganese dioxide (MnO 2 ) 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 MnO 2 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 Mn 2+ suppressed formation of PbO 2 on anode surface.