Reductive dissolution of manganese from manganese dioxide ore by autotrophic mixed culture under aerobic conditions

Reductive leaching of manganese from manganese dioxide ore has become increasingly important for production of electrolytic manganese. The anaerobic bioleaching has long received great concerns for reductive extraction of Mn by heterotrophic microorganisms in the presence of sacchariferous substances. Alternatively, the reductive dissolution of manganese from manganese dioxide ore by autotrophic mixed culture under aerobic conditions was investigated in this work. The results showed that the autotrophic mixed culture was capable of reductive liberation of Mn in the presence of cheap sulfur and pyrite. 99% of Mn extraction was achieved by the mixed culture at 10% of pulp density after 72-96 h under 24 g/L of mixed energy substrates, initial pH at 1.0 and pH control of process at 2.0. The diffusion controlled model fitted best for describing dissolution of Mn. The acid dissolution was the dominating mechanism for great improvement in leaching efficiency from 78% without pH control to 99% with pH control.