Selective Extraction of Rare Earth Elements Over TiO 2 From Bauxite Residues After Removal of Their Fe-, Si-, and Al-Bearing Constituents

摘要

In our previous study, an intermediate material enriched with multiple rare earth elements (REEs, e.g., La~(2)O~(3), Ce~(2)O~(3), Sc~(2)O~(3), and Y~(2)O~(3)) and TiO~(2)was obtained after removing iron, silica, and alumina from bauxite residues. For valorization of this valuable intermediate material, the selective leaching and separation of REEs and TiO~(2)by phosphoric acid leaching was investigated. Approximately 90% of REEs was leached from the material using 8- to 10-mol/L H~(3)PO~(4)liquor at 150°C, while 98% of TiO~(2)was precipitated as Ti(HPO~(4))~(2)·H~(2)O in the leached residue, achieving selective extraction of REEs over TiO~(2). Scrubbing with dilute H~(3)PO~(4)liquor during filtration could facilitate the formation of Ti(HPO~(4))~(2)·H~(2)O. The high extraction of REEs was a result of their distribution in the perovskite lattice, as demonstrated by the positive correlation between dissolutions of REEs and perovskite. A route for stepwise extraction of Fe, Si, Al, REEs, and Ti from bauxite residue was established.