Strategy for possible separation of light rare earth elements (La, Ce, Pr, Nd) from synthetic chloride solutions by oxidative precipitation, solvent extraction and stripping

Abstract

Due to their comparable physicochemical characteristics, light rare earth elements (LREEs), such as lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd), the separation of these elements is a challenging process. In this study, a strategy involving hydrometallurgical unit operations is presented, including oxidation, precipitation, solvent extraction (SX), and stripping. Separation of Ce(III) can be achieved by selective oxidation with potassium permanganate (KMnO4), which is a strong oxidizing agent and proven to be effective in selectively precipitating Ce(III). By using solvent extraction with 0.5 mol L−1 of Cyanex 572 at an A/O ratio of 1:3 and four stages in a counter-current configuration, La(III) can be separated from Nd(III) and Pr(III) with 100% and 99% extraction, respectively. Cross-current scrubbing with a low concentration of HCl can be used to remove La(III), which becomes the contaminant that is left in the loaded organic. Other mineral acids, including HNO3, H2SO4, and H3PO4 were also investigated as alternative scrubbing/stripping agents.