Electrorefining of high purity manganese

Abstract

The recovery of manganese metal from manganese chloride medium by purification–electrorefining was studied. The ammonium chloride – manganese chloride electrolyte was selected as the most promising for refining. The physical properties of the electrolyte were first studied as a function of solution composition and temperature. The electrorefining process introduces impurities into the anolyte from the dissolving anode. It is necessary to purify the anolyte before passing the solution to catholyte. The purification of the electrolyte by ion exchange was investigated. This paper reports the uptake of copper, nickel, cobalt, cadmium, zinc and manganese from manganese chloride solution onto the chelating resin Lewatit® MDS TP220 in batch and column experiments. The results demonstrate the ability for Lewatit® MDS TP220 to remove contaminants to an extent satisfying the quality criteria required for the utilization of the manganese chloride solution for electrorefining. In the electrorefining process, the synergistic effects of selected impurities on manganese deposit quality were first investigated. The parameters of current density, deposition time, and cathode usage frequency on the electrorefining process were investigated. With increasing the current density, the cathodic current efficiency first increased, reached a maximum value and then decreased. With increasing deposition time from 24h to 48h, the manganese current efficiency decreased and the deposit became more dendritic. The more times the cathode was used, the lower the current efficiency.