Iron Extraction from Red Mud using Roasting with Sodium Salt

• Published in: Mineral processing and extractive metallurgy review Vol. 42; no. 3; pp. 153 - 161
• Main Authors: Wei, Ding, Jun-Hui, Xiao, Yang, Peng, Si-Yue, Shen, Tao, Chen
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 03-04-2021; Taylor & Francis Ltd
• Subjects: Aluminosilicates; Aluminum; Aluminum oxide; Aluminum silicates; Bauxite; Bayer process; Chemical reactions; Concentrates (ores); Fayalite; Food processing; Iron oxides; Iron silicates; Light microscopy; Magnetic separation; Metal industry; Microscopy; Mud; Optical microscopy; Recovery; Red mud; Roasting; Scanning electron microscopy; segregation roasting; Silica; Silicon dioxide; Slag; Sodium; Sodium salts; Sodium silicates; Sodium sulfate; Solid wastes; Spectroscopy; Sulfates; X-ray diffraction
• ISSN: 0882-7508; 1547-7401
• DOI: 10.1080/08827508.2019.1706049

Red mud is the main solid waste generated by the aluminum industry for the extraction of alumina. Considering the environmental problems associated with red mud, the recovery of iron from bauxite slag is still a promising field. The effect of sodium sulfate on the red mud separation roasting-magnetic separation process was studied. The results show that at the roasting temperature of 1100°C for 65 min, the segregation roasting-magnetic separation is carried out with 8 wt.% sodium sulfate. The total iron grade of the magnetic separation iron concentrate is 79.32 wt.% and iron recovery rate of 85.43%. X-ray diffraction analysis (XRD), optical microscopy analysis and scanning electron microscopy-X-ray energy spectroscopy (SEM-EDS) were used to study the addition of sodium sulfate segregation roasting products to red mud. The results show that adding the proper amount of sodium sulfate during the red mud segregation roasting process can enhance the separation and recovery of iron. During the red mud segregation roasting process, sodium sulfate reacts with alumina, silica, etc. to form sodium silicate and sodium aluminosilicate, which inhibits the formation of fayalite and promotes the chlorination of iron oxide. Element migration and chemical reaction can destroy the original ore structure, promote the formation of molten phase and accelerate the aggregation and growth of metallic iron particles. Thus, a metallic iron concentrate with high quality is obtained.