Extraction of manganese from iron rich MnO2 ores via selective sulfation roasting with SO2 followed by water leaching

•Manganese dioxide is selectively sulfated forming MnSO4 by roasting with SO2 as reductant.•Iron oxide remains unsulfated under SO2–N2 atmosphere.•MnSO4 is extracted by water leaching while maintaining iron in the residue.•Effects of roasting and leaching parameters on manganese/iron extraction are investigated.

Manganese oxide ore is one of the most important resources. Owing to the depletion of high-grade ores, attention has turned to low-grade ones containing multiple elements such as iron, silicon, and aluminum. Conventional processes for extracting manganese are characterized by high production costs, intensive energy consumption, heavy environmental issues, or high co-leaching of impurities. In this study, selective sulfation roasting–water leaching is proposed for recovering manganese from iron rich low-grade manganese oxide ores using SO2 as reductant. Thermodynamic analysis indicated that manganese dioxide is readily transformed to sulfate. However, the sulfation of ferric oxide only occurs in the presence of both SO2 and O2. The thermodynamic stability region for MnSO4 and Fe2O3 demonstrated selective sulfation of manganese dioxide is feasible. The experimental validation for sulfation roasting and water leaching revealed that 90.6% of manganese and only 3.5% of iron were extracted when sulfation roasting was conducted at 500 °C for 60 min with SO2 partial pressure (SO2 / (SO2 + N2)) of 0.5%–1.0% (Vol.), and the leaching process was performed at 50 °C for 15 min with liquid-to-solid ratio of 5. This process is able to recover manganese from various low-grade manganese oxide ores.

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