Enrichment of ScO and TiO from bauxite ore residues.

As a major byproduct generated in the alumina industry, bauxite ore residue is an important reserve of scandium and titanium. In this study, the feasibility and mechanism of enriching ScO and TiO from a non-magnetic material, which was obtained from carbothermal reductive roasting and magnetic separation of bauxite ore residue, were investigated based on a two-step (acidic and alkali) leaching process. It was revealed that approximately 78% SiO and 30-40% of CaO, FeO and AlO were removed from a non-magnetic material with 0.0134wt.% ScO and 7.64wt.% TiO by phosphoric acidic leaching, while about 95% AlO and PO were further leached by subsequent sodium hydroxide leaching of the upper-stream leach residue. A ScO-, TiO- rich material containing 0.044wt.% ScO and 25.5wt.% TiO was obtained, the recovery and the enrichment factor of ScO and TiO were about 85% and 5, respectively. The enrichment of ScO was attributed to higher pH (>3.3) of phosphoric acid solution than its dissolution pH, and the enrichment of TiO was mainly associated with the insoluble perovskite (CaTiO) in the acidic solution at ambient temperature. As ScO and TiO cannot be dissolved in the alkali solution, they were further enriched in the leach residue.