Recovery of Scandium, Aluminum, Titanium, and Silicon from Iron-Depleted Bauxite Residue into Valuable Products: A Case Study

Bauxite residue is a high-iron waste of the alumina industry with significant contents of scandium, aluminum, and titanium. This study focuses on the recovery of Sc, Al, Ti, and Si from iron-depleted bauxite residue (IDBR) into valuable products. Iron depletion was carried out using reduction roasting followed by low-intensity magnetic separation to enrich bauxite residue in Al, Ti, and Sc and reduce an adverse effect of iron on scandium extraction. Hydrochloric high-pressure acid leaching, aluminum precipitation by saturation of the acid leachate, solvent extraction of scandium using di(2-ethylhexyl) phosphoric acid (HDEHP) and tributyl phosphate (TBP), alkaline leaching of the acid residue with subsequent silica precipitation were used to obtain appropriate selective concentrates. As a result, scandium concentrate of 94% Sc2O3, crude alumina of 93% Al2O3, titanium concentrate of 41.5% TiO2, and white carbon of 77% SiO2 were prepared and characterized. Based on the characterization of the treatment stages and the obtained valuable products, the prospect for the application of the suggested flowsheet was discussed.