Extraction of rare earth ions from Nd-Fe-B magnet wastes with TBP in tricaprylmethylammonium nitrate

Abstract

Rare earth (RE) ions such as Pr(III), Nd(III) and Dy(III) derived from spent Nd-Fe-B magnets were extracted from an aqueous phase containing nitrate ions by tri-n-butyl phosphate (TBP) with an ionic liquid (IL), tricaprylmethylammonium nitrate ([A336][NO3]). It was confirmed that the extraction of RE(III) was enhanced by adding NaNO3 into the aqueous phase and continuous extraction by a batch system led to Nd(III) enrichment in the IL phase. When using Nd-Fe-B magnet wastes including iron oxide, a wet separation process was required for removal of the iron from a solution in which the metal ions were leached. The process led to a relatively low RE(III) concentration in the prepared solution due to an increase in its volume by adding base for precipitation of Fe(OH)3. RE(III) recovered from wastes in the absence of iron oxide by a dry separation process were more concentrated in nitric acid. With the feed solution as the aqueous phase, Nd(III) was distributed significantly into the IL phase through repeated extractions.