Technique for recovering rare-earth metals from spent sintered Nd-Fe-B magnets without external heating

Abstract

To selectively recover rare-earth metals with higher purity from spent sintered Nd-Fe-B magnets without external heating, we investigated the mechano-chemical treatment of spent sintered Nd-Fe-B magnet powder with a reaction solution of HCl and (COOH)2 at room temperature. The results of various experiments showed that the mechano-chemical treatment with HCl and (COOH)2 is very effective for recovering the rare-earth metals contained in spent sintered Nd-Fe-B magnet powder; the recovery rate and purity of the rare-earth metals were 95.3 and 95.0 mass%, respectively, under optimal conditions ([HCl] = 0.2 mol/dm3 and [(COOH)2] = 0.25 mol/dm3).