Enrichment of the manganese to iron ratio of ferruginous low-grade manganese ore using solid reductant

Abstract

Low-grade manganese ores with low Mn/Fe ratios can be enriched through selective carbon reduction of iron oxide to magnetite followed by magnetic separation of the magnetite. Thermogravimetric analysis(TGA) was used to assess the preferential isothermal reduction of pure MnO2 and Fe2O3 using solid carbon. This was followed by reduction of a synthetic analogue of composition comparable to an actual low-gl-ade ore (i.e., Sandur manganese ore, Sandur, India). The carbothermic reduction of the manganese ore converts the hematite and goethite minerals to magnetite (Fe3O4), with the magnetite then going into the magnetic fraction.. The resultant nonmagnetic fraction becomes depleted of iron with an enhanced manganese content. These results show that it is possible to reduce the iron from 22% to 5.85%, thus increasing the Mn/Fe ratio from 1.52 to 6.2 with a manganese recovery of about 50%. The recovery was further improved by grinding the magnetic fraction to -75 mu m.