Comprehensive Recovery of Iron and Aluminum from Ordinary Bayer Red Mud by Reductive Sintering–Magnetic Separation–Digesting Process

Iron and aluminum in red mud were recovered by a reductive sintering–magnetic separation–digesting process. The raw materials were composed of ordinary Bayer red mud, MgO, Na2CO3 and C, in which MgO and Na2CO3 were used as mineralizing agents, and C as a reductive agent. Sintering orthogonal experiments showed that 55.03% content of iron concentrate with 91.02% iron recovery could be obtained using sintering conditions of 1200°C for 90 min and mole ratio (MgO/SiO2) of 1.3. Following magnetic separation of the sintered product, orthogonal experiments on the digestion of the nonmagnetic residue showed that the highest aluminum recovery, 70.15%, was achieved using digesting conditions of 90°C, 20 min and 3% NaOH concentration. Analysis of the recovered products showed that Fe2O3 and Al2O3 can be transformed simultaneously into Fe and NaAlO2 phases, and most of the iron aggregates in the larger metallic particles in the sintering process contribute to the high iron recovery.