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Abstract

Bauxite ores used in aluminium oxide production via the Bayer process contain trace elements (REEs, V, Li, Sc, Ga) currently not valorised. Vanadium and Gallium dissolve during the Bayer process forming impurities in the Bayer liquor (sodium aluminate solution). Vanadium application ranges from steel to aircraft industries, and extraction involves ammonium treatment of strip liquor for vanadium salt (AMV, V₂O₅) precipitation. Current crystallization techniques have drawbacks of generating voluminous, highly saline wastewater. This study investigated the use of antisolvent (acetone) crystallization with synthetic solutions as an alternative to the crystallization and calcination step in the conventional production of high purity vanadium salts. The yield, purity, and product characteristics of the crystals for different final organic to aqueous (O/A) ratio at constant addition rate of antisolvent at room temperature have been investigated. A batch time-dependent effect was observed with the best product quality, in terms of size and crystal habit (dominated by hexagonal laths), being attained when t_b ≤ 2 h at an O/A ratio of 0.5. The early onset of acicular crystal formation and higher yields (≥ 97%), along with higher impurity incorporation into the solid phase, was observed at an O/A ratio of 0.75, and this was attributed to higher levels of supersaturation.