Processing of Spent Titanium Chlorinator Melt for Scandium Recovery.

Spent titanium chlorinator melt is a potential technogenic source of scandium, but its recovery is complicated by high contents of iron, aluminium and alkali and alkaline-earth chlorides. This study assessed a sequence of hydrochloric acid leaching, Fe(III) reduction with ascorbic acid, sorption on the strong-acid cation exchanger Lewatit MonoPlus SP112H, desorption with acidified ammonium sulfate solution, oxalate precipitation, calcination and an additional column purification. In a scaled-up test, leaching of 4 kg of the spent melt with 5% HCl produced 25.5 L of filtrate containing 475.30 mg Sc. Two-stage sorption recovered 90.9% of the scandium, and the overall desorption degree reached 94.8%. The kinetic data were better described by the non-linear pseudo-second-order model (R2 = 0.890-0.938). Precipitation and calcination gave 0.60 g of an intermediate oxide product with 65.0 wt% Sc, and the additional purification 0.45 g of a final oxide product in which X-ray diffraction identified cubic Sc2O3 as the predominant crystalline phase; the elemental analysis gave a purity close to 98 wt%. Recovery into the final oxide reached 61.92% of the scandium in the filtrate. Iron co-sorption and scandium losses during the additional purification remained the principal limitations of the process.