The role of calcium-based additives in extracting iron from red mud through carbothermic reduction

Abstract

Increasing aluminum demand has increased the red mud, a bauxite residue of the Bayer process. It contains valuable elements, such as iron, titanium, vanadium, and a small amount of rare-earth elements. Utilization of red mud is required to prevent environmental damage. In this work, the carbothermic reduction was followed by magnetic separation of red mud to extract iron. The effects of calcium-based additives, i.e., CaCl2 and CaF2, on recovery and metallization degree, as well as on phase transformation and morphology of iron particles in reduced pellets, were investigated. The red mud, coal, and additives were mixed homogeneously and pelletized into a diameter of 10 mm. The reduction process was carried out in a muffle furnace at 1050-1250 °C for 60 minutes. Furthermore, the reduced pellet was ground and a magnetic separation process was conducted to separate the iron metal from its gangue. The results showed that CaF2 performed better than CaCl2. The optimum result was obtained by adding 8% CaF2 and a 1.0 stoichiometric amount of coal to the carbothermic reduction of red mud at 1250 °C for 60 minutes. It generated iron grade, recovery, and metallization of 83.64%, 98%, and 93.5%, respectively.