Recovery of Fe Element from Red Mud by Sodium Roasting and Alkaline Leaching

The paper investigates the treatment of ferric red mud through sodium roasting and alkaline leaching. The Al element in the red mud was removed, and the alkaline leaching residues were relatively pure Fe₂O₃. A novel approach was developed to enhance the retrieval of Fe element from high iron red mud by synthesizing sodium ferrate using alkaline leaching residues. When the roasting temperature is 850 ℃ and the roasting time is 3h, the leaching result of Al is the best, with a leaching rate can reach 96.28%. In the leaching process, NaAlO₂ is completely leached, Na_0.68Fe_0.68Si_0.32O₂ is dissolved in the alkali solution, and Fe₂O₃ is formed. After the removal of Al element, Na₂FeO₄ solution with concentration of 2494mg/L is successfully prepared by alkaline leaching residues. In addition, promotional mechanisms of sodium roasting on leaching of soluble salts are discussed from the perspectives of thermodynamic reactions and phase compositions. The aim of this research is to efficiently utilize the Fe element in high iron red mud and explore new application prospects for more effective use of solid waste resources in alumina industry in China.