Enhanced selective leaching of scandium from red mud

Abstract

Selective leaching of Sc from red mud is particularly important for both solid waste treatment and reclamation of rare earth elements. This work developed a new method for selective acid leaching of Sc and Fe from red mud. Ethylene diamine tetraacetic acid (EDTA) was chosen as the chelating agent to re-distribute the species of Sc and Fe ions in the leaching process, which greatly enhanced the selectivity of Sc over Fe. EDTA–enhanced selective leaching of Sc from red mud using diluted hydrochloric acid was achieved under the optimal experimental conditions: ratio of leaching agent (HCl + H2O): red mud: EDTA was 40 mL: 10 g: 2 g, and HCl dosage was 40% of theoretical value at temperature 70 °C and reaction time 4.0 h. The leaching efficiencies of Sc and Fe were 79.6% and 6.12% respectively. The Sc/Fe leaching efficiency ratio was greatly improved with the involvement of EDTA, which made the subsequent separation of Fe and Sc easier. Furthermore, this work may provide an alternative way for the recovery and separation of valuable metals from solid wastes.