Extracting Al2O3 from red mud smelting separation slag based on mineral phase reconstruction

Recovery of valuable metals from red mud smelting separation slag is important for environmental protection and saving of natural resources. In this paper, we propose a recycling process of red mud smelting separation slag by mineral phase reconstruction conducted under an air atmosphere. In this process, NaOH and Ca(OH) 2 roasting of Al 2 O 3 and NaAlSiO 4 was performed, and Al 2 O 3 and SiO 2 were converted into alkaline-soluble NaAlO 2 and Ca 2 SiO 4 , respectively. In the consequent steps, more than 80% of Al 2 O 3 was selectively dissolved into a leaching solution using a NaOH solution under 95℃, and the obtained NaAlO 2 solution can be used as a source for extracting alumina. Then, a 20 wt.% HCl solution was used to remove SiO 2 from the residue, obtaining a SiO 2 -containing solution and a concentrated residue of undissolved TiO 2 and CaO. Finally, this mineral phase reconstruction process can enable a higher metal leaching rate, and this study provides a novel, clean, and sustainable method for recycling valuable metals from red mud smelting separation slag.