Recovery of neodymium and praseodymium from nitrate-based leachate of permanent magnet by solvent extraction with trioctylphosphine oxide

Abstract

For recovery of the rare earth elements neodymium and praseodymium from end-life permanent magnets, solvent extraction experiments were carried out on the nitrate-based leachate with trioctylphosphine oxide (TOPO) as an extractant. TOPO selectively extracted Nd and Pr in preference to Fe at higher HNO3 concentration. Nd and Pr extracted into TOPO were selectively stripped using HCl solution, and the small amount of co-loaded Fe was stripped with ammonium oxalate solution after removal of Nd and Pr. McCabe-Thiele diagrams for the extraction and stripping of Nd/Pr were constructed. The results were validated in counter-current simulation experiments using real leachate solution. Finally, a process for recovering Nd and Pr from the nitric acid leachate of permanent magnets was proposed.