Rare earth elements recovery from alumi̇num plant residues

The Bayer process, which extracts alumina from bauxite ore, generates significant amounts of red mud, posing environmental challenges due to its high alkalinity and heavy metal content. Red mud was identified as a secondary source of REEs through chemical characterization. Washing the samples reduced alkalinity and enhanced REE concentration. Kinetic tests determined optimal leaching durations for maximum REE recovery. Optimal leaching conditions were identified for hydrochloric acid (HCl), nitric acid (HNO3), and sulfuric acid (H2SO4). For HCl, the best results were at 90°C, 3 M concentration, and a 2% solid-to-liquid ratio, yielding high recovery rates for Ce (90%), Y (100%), Sc (99.2%), La (74.1%), and Nd (56.7%). HNO3 leaching at 90°C and 6 M concentration achieved recoveries of Ce (72.3%), Y (68.8%), Sc (87.7%), La (91.8%), and Nd (98.7%). H2SO4 was most effective at 90°C, 3 M concentration, with recoveries of Ce (100%), Y (73.04%), Sc (100%), La (91.12%), and Nd (97.63%). And during Fe precipitation, REEs co-precipitated effectively, with Cerium showing the highest efficiency (89.9%). Keywords: Metal Recovery, Hydrometallurgy, Red Mud, Rare Earth Elements, Critical Metals.