Yttrium Recovery Process from Leaching Solution of Spent Ni-MH Batteries Using Coprecipitation and Solvent Extraction

In this study, we investigated an efficient recovery method of yttrium from a sulfuric acid leaching solution of spent Ni-MH battery electrode materials. In this newly proposed method, yttrium, one of the heavy rare earths (HREEs), was coprecipitated with light rare earths (LREEs) in the preliminary crude separation, and the residual yttrium was precisely recovered by solvent extraction using di-(2-ehylhexyl) phosphoric acid (D2EHPA) as the extractant. Yttrium in the leaching solution of 0.7 g/L that remained at 0.2 g/L after the coprecipitation operation; however, it could be reduced to 0.001 – 0.002 g/L by the solvent extraction process in the following step. In this technical report, we focused on the solvent extraction operation. The extractant, D2EHPA, has a high affinity for yttrium, and we confirmed the possibility of improving the recovery yield of yttrium from 43% by coprecipitation alone to 98% by introducing solvent extraction.