A study on separation of Mn and Fe from high-alumina ferruginous manganese ores by the carbothermal roasting reduction process

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Carbothermal reduction followed by magnetic separation has been recognized as an effective recovery strategy to achieve separation of Mn and Fe from ferruginous manganese ores (Fe-Mn ores). However, it is difficult to improve the recovery of manganese more than 85% by changing carbothermic roasting reduction and magnetic separation. This work clarified the underlying reason for the poor separation with the magnetic separation process and proposed a promising process for the recovery of Fe and Mn from Fe-Mn ore. The effect of operating variables on recovery and separation of Mn and Fe from Fe-Mn ore is initially investigated during the carbothermic reduction roasting process followed by magnetic separation to reveal the underlying reason for the poor separation from Fe-Mn ores. Then, the stepwise reduction behaviors of the MnO-Fe2O3 and MnO-Fe2O3-Al2O3 systems were investigated to clarify that the formation of composite oxide Mn1−xFexO (0 < x < 0.497) and hercynite (FeO·Al2O3) directly caused the poor separation of Fe and Mn from high-alumina Fe-Mn ores. Then, the stepwise reduction roasting behaviors of Mn1−xFexO and FeO·Al2O3 were investigated by XRD, SEM-EDS and XPS analysis. After adjusting the experimental parameters, iron-rich products with a Fe recovery of 94.31% and a grade of 85.21% and manganese-rich product with a Mn recovery of 90.05% and a grade of 54.35% are obtained. The mass ratio of Mn/Fe increased to 8.5 in the manganese-rich product.