Systematic study on separation of Mn and Fe from ferruginous manganese ores by carbothermic reduction roasting process: Phase transformation and morphologies

Abstract

Abstract Carbothermic roasting reduction followed by magnetic separation process is reported as an effective technological process to separation and recovery of Fe and Mn from low-grade ferruginous manganese ores (Fe–Mn ores) as an acceptable feed to meet the demands of the developing manganese industry. In this study, the effects of operating variables on the recovery and grade of Fe and Mn are initially investigated during the carbothermic roasting reduction process followed by magnetic separation. Then, the phase transformation and morphologies of spinel (FeyMn1−y)Al2O4, fayalite FeyMn2−ySiO4 and (FeO)x(MnO)1−x are investigated by SEM-EDS, XRD, TG/DTG and thermodynamic analyses. Finally, the stepwise reduction and interfacial reaction of three types of phases are investigated at 700–1100\u202f°C for 10–120\u202fmin to clarify the reason for the poor separation of Mn and Fe from Fe–Mn ores. The effect of MnO on the stepwise reduction behavior of Fe2SiO4 and FeAl2O4 is analyzed in detail. Finally, the tight integration of the MnO phase with a metallic Fe–Mn alloy derived from the stepwise reduction of (FeO)x(MnO)1−x are closely associated with the stepwise reduction of the FeyMn2−ySiO4, (FeyMn1−y)Al2O4 and (Fe,Mn)2O3 phases. In addition, the formation mechanism and the interfacial reduction reaction of (FeO)x(MnO)1−x, (FeyMn1−y)Al2O4 and FeyMn2−ySiO4 are systematically analyzed to show the effect of the MnO phase on the stepwise reduction of the Fe2SiO4 and FeAl2O4 phases. Finally, some suggestions were recommended for the carbothermic reduction followed by magnetic separation for utilizing the Fe–Mn ores effectively. The manganese-rich product an acceptable feed containing 53.60\u202fwt.% total Mn with the Mn recovery of 89.38% and mass fraction of Mn/Fe of 5.43 are obtained.