Hydrometallurgical Recycling of Red Mud to Produce Materials for Industrial Applications: Alkali Separation, Iron Leaching and Extraction

Red mud is a polymetallic waste generated during Bayer's process of alumina production. High alkalinity (pH > 11), multiple elements, and micron-sized particles make red mud recycling energy-intensive and challenging. The following work presents a hydrometallurgical flowsheet for separation of different red mud elements and recovery of high purity Fe (II) product using cost-effective reagents, energy-efficient processes, and minimal waste generation. Red mud preprocessing was carried out by mild hydrochloric acid wash (1 M, 13 pct pulp density, 40 °C 15 minutes), followed by leaching of hematite from neutralized red mud in oxalic acid (2 M, 10 pct pulp density, 95 °C, 2.5 hours). UV light-assisted photochemical reduction of oxalic leach solution of red mud separated more than 98 pct Fe in the form of ferrous oxalate (purity more than 99 pct) within 5 hours. The process's material balance shows a overall recovery of more than 85 pct Fe value as solid ferrous oxalate of high purity and concentrating titanium oxide in the residue and aluminum in the leaching solution.