Selective extraction of scandium from bauxite residue using ammonium sulfate roasting and leaching process

Abstract

Bauxite residue, as an important source of scandium, is an alkaline industrial waste generated during the Bayer process for alumina production. A novel method for selective extraction of scandium from bauxite residue was proposed by ammonium sulfate roasting and water leaching. During the roasting process, ammonium sulfate could selectively react with Sc, Al and Fe in the bauxite residue to produce respective metal ammonium sulfates, and then which were completely decomposed to their respective metal sulfates at 550 °C. The sulfates of iron (III) and aluminum were decomposed to their respective metal oxides at about 700 °C, whereas the scandium sulfate remained stable. In the leaching process, the scandium sulfate could be selectively leached with water from roasted residues while other elements mainly remained in the leaching residue. The extraction efficiency of scandium reached above 90% under the optimum conditions.