Electrochemical Quartz Crystal Microbalance Investigation of Manganese Oxide Deposition in Sulfuric Acid Relevant for Zinc Electrowinning

Abstract

The deposition and dissolution of manganese oxide from a sulfuric acid solution were investigated by conventional electrochemical techniques and EQCM on gold and platinum electrodes. The product of the oxidation was found by EQCM to be MnO2 at a higher potential (1.55 V), whereas a mixture between MnOOH and MnO2 was produced at a lower potential (1.45 V). An ECE mechanism involving the formation of MnOOH was proposed as the oxidation mechanism. A higher deposit porosity was obtained at the higher deposition potentials. The reduction mechanism was proposed to involve an electrochemical reduction of MnO2 to MnOOH, followed by a chemical reaction yielding Mn2+ and MnO2.