The effect of carbothermal reduction on the physical and chemical separation of the red mud components

• Recovery of RM using a combination of physical and chemical processes was studied. • Fe was effectively separated by carbothermal reduction and magnetic separation. • Carbothermal reduction of RM adversely affected the leaching of Ti and REEs . Red mud is a waste generated during the Bayer process in the production of alumina. Recovery of metallic components of the red mud has both environmental and economic benefits. In this study, the effect of carbothermal reduction on the physical and chemical separation of red mud components, namely Ti, REEs, Fe, and Al, were investigated. At first, the impact of carbothermal reduction on the efficiency and selectivity of iron separation from the bulk material through magnetic separation was studied. At the optimum conditions of T = 1350 °C, using a ring-shaped mixing regime of coal and red mud, coal/red mud ratio of 3, t = 120 mins, and soda ash/red mud ratio of 0.2, the iron content of the red mud was effectively metalized and separated from Ti, REEs, and Al. Recovery of iron in the magnetic separation concentrate was 91%, with Fe content of 81%, while about 90% of Ti and Al and 80% of REEs were retained in the non-magnetic product. For the untreated sample, however, iron separation was insignificant mostly due to the low iron metallization. Finally, the dissolution behavior of Ti, REEs, Fe, and Al for both treated and untreated samples using H 2 SO 4 , HCl, and HNO 3 were studied. Different dissolution behavior of the REEs and Ti were observed and correlated to the mineralogical composition of the sample. Overall, carbothermal reduction has shown to positively affect the magnetic separation of iron but negatively affected the Ti and REEs dissolution efficiency.