Reductive leaching of blended manganese carbonate and pyrolusite ores in sulphuric acid

Abstract

Direct leaching of manganese from pyrolusite using low-grade manganese carbonate as a reducing agent in dilute sulphuric acid was investigated by blending pyrolusite with manganese carbonate ore, which has the reductant ferrous carbonate. The effects of leaching temperature, sulphuric acid concentration, leaching time, stirring speed, particle size etc. were considered. The results generally show that as the various parameters increase, the recovery of Mn increases while Fe decreases. A blend ratio of 5 : 1 by weight of manganese carbonate-pyrolusite gave 96% maximum extraction of manganese by the following conditions: leaching time of 120 min, leaching temperature of 70°C, stirring speed of 300 r/min, particles size of +150 mesh, liquid-solid ratio of 14 : 1 and acid concentration of 200 g/L. The leaching process followed a first-order reaction and the rate constant with respect to manganese was found to be 0.33 h−1 with activation energy of 9.5 kJ/mol.