The mechanism on reducing manganese oxide ore with elemental sulfur

Abstract

Extraction of Mn from manganese oxide ore via sulfur-based reduction followed by acid leaching has received much attention. In this study, the mechanism on reducing manganese oxide ore with elemental sulfur was investigated. The reduction of manganese dioxide by sulfur is feasible thermodynamically, and the experimental validation proved that manganese dioxide was reduced stepwise to low-valence state in the order of MnO2 → Mn2O3 → Mn3O4 (together with MnSO4 or SO2). Subsequently, Mn3O4 would be reduced to form MnS or MnO, and the tendency of forming MnO was enhanced with increase in the temperature. Manganese oxide (MnO) will further react with excessive sulfur forming MnS and MnSO4. However, the formed MnS on the surface of the particles would inhibit further reduction or sulfidation. During the reductive roasting process, MnSO4 as well as gaseous SO2 were simultaneously generated. The reaction between MnS and Mn3O4 occurred at temperatures over 500 °C, which facilitated producing MnO and SO2. The roasted product contained MnS, MnSO4, MnO and unreacted Mn3O4 at lower temperature (<500 °C), whereas the main products were MnO and MnSO4 at higher temperature (≥500 °C). The content of MnO increased gradually while that of MnS was decreased by increasing the roasting temperature.