Equilibrium distribution of Mg in manganese electrolysis system

Aiming at the common problems of magnesium ion concentration being higher than manganese ion concentration in the electrolytic manganese industry, the equilibrium distribution of Mg in manganese electrolysis system was studied. It mainly included four main steps: the rhodochrosite was leached under acidic conditions, the Fe2+ was removed by precipitation after MnO2 oxidation, the heavy metals ware removed by SDD. Finally, the manganese metal was produced in the cathode by electrolysis of manganese sulfate solution. The morphology and phase composition of magnesium in the whole system were obtained by SEM and XRD. Under leaching conditions for industrial production, the temperature was 85 °C, liquid-solid ratio was 8:1, the excess coefficient of acid was 1.3, and the reaction time was 3 h, leaching rate of Mg was 38.19%, and the corresponding concentration of Mg2+ was 2.96 g l−1 in the solution. The effect of Mg2+ concentration on manganese leaching rate was done, the result showed that the leaching rate of manganese decreased with the increasing of magnesium ion. When the Mg2+ was increased from 0% to 50%, the leaching rate of manganese decreased from 83.12% to 76.39%. At pH 5.5 and 85 °C, Fe2+ could be completely removed by using MnO2 as oxidant and 22.44% magnesium would be taken away with iron slag. The removing of heavy metals could be achieved under the condition of 60 5 °C, SDD dosage 3‰ (according solution quantity) and 1 h, 0.4% magnesium would be taken away with heavy metal slag. The electrolysis experiments were carried out under the conditions, (NH4)2SO4 content was 100 g l−1, pH was 7.2, reaction temperature was 45 °C and current density was 350 A m−2. The results showed that 88.18% of magnesium was distributed in the anode solution and 11.4% in the cathode solution, and there was 0.08% and 0.34% of magnesium in the cathode manganese sheet and the anode slag, respectively.