Manganese extraction by sulfur-based reduction roasting–acid leaching from low-grade manganese oxide ores

In recent years, the comprehensive utilization of low-grade manganese oxide ores has received much attention due to the shortage of high-grade manganese ore resources. In this study, low-grade manganese oxide ores were treated by reduction roasting using chemically pure sulfur as a reductant. Then, the roasted samples were subjected to sulfuric acid leaching to extract manganese (Mn). The effects of roasting temperature, roasting time, S/Mn mole ratio, sulfuric acid concentration, leaching temperature, stirring rate, leaching time and liquid-to-solid ratio on the Mn and Fe leaching were discussed. The leaching efficiencies of 95.6% for Mn and 14.5% for Fe were obtained under the following optimized conditions: 550 °C of roasting temperature, 10 min of roasting time, 0.50 of S/Mn, 1.0 mol/L of sulfuric acid concentration, 25 °C of leaching temperature, 200 r/min of stirring rate, 5 min of leaching time and 5:1 of liquid-to-solid ratio.

► Sulfur is an effective reductant for extracting Mn from manganese oxide ores.
► The Mn and Fe leaching ratios are 95.6% and 14.5%, respectively.
► Main reactions between manganese oxides and sulfur when roasted are analyzed.
► There was no harmful H2S gas emitted in the acid leaching process.