Rare-Earth Elements Recovery from Nd-Fe-B Hard Magnets by Hydrometallurgical Processes

In this study, a hydrometallurgical process was evaluated for the recovery of Nd from a Nd-Fe-B magnet. Each leaching test was performed at the solid (weight) to liquid (volume) ratio of 1:50 and was mixed at 400 rpm at ambient temperature. The effects of 3 different acids (HCl, HNO3, and H2SO4) on the extraction of Nd were investigated and H2SO4 was found to be more effective than other acid solutions. Under the optimal conditions, pregnant leach solution was produced with H2SO4 for subsequent Nd precipitation testing. Each precipitation test was carried out using 100 mL of feed solution mixed at 600 rpm at 25 °C. NaOH and H2C2O4 were used for Nd precipitation. The highest Nd was precipitated as Nd2(C2O4)3·10H2O with C2H2O4 at 20 min.