Utilization of red mud: Recovery of iron and aluminum by enhanced separation based on a new combined roasting process

Red mud (RM) is a strongly alkaline solid waste produced during the production of alumina from bauxite. China's RM stockpile exceeds 1 billion tons, with an annual output of over 100 million tons. However, the comprehensive utilization percentage is less than 10%, and the rest are stored around alumina plants, which are severely burdening land and the surrounding environment. This study proposes a combined roasting process, which combines soda roasting with medium-temperature magnetization roasting, to synchronously convert minerals in RM into magnetite and soluble aluminate, to achieve the goals of iron concentrate upgrading and aluminum recovery. Iron concentrate with of yield of 72.52 wt%, total iron (TFe) concentration of 63.84 wt%, iron recovery of 93.47 wt%, and aluminum concentration of 2.53 wt%, and the aluminum product with the Al₂O₃ concentration of 99.49 wt% were obtained under the optimized process parameters. Four pathways to iron concentrate upgrading that reduce the aluminum concentration during combined roasting are proposed based on the non-isothermal kinetic analysis and phase evolution results. These results can provide theoretical support for the comprehensive utilization of iron and aluminum in RM.