Improvement of metal separation process from synthetic hydrochloric acid leaching solution of spent lithium ion batteries by solvent extraction and ion exchange

Abstract

Spent lithium-ion batteries (LIBs) are good secondary resources for recycle and reuse. To develop a process for the separation of Cu(II), Co(II), Mn(II), Ni(II) and Li(I) with high purity from spent LIBs and circumvent some drawbacks of the previous work, solvent extraction and ion exchange experiments were done in this work. The synthetic hydrochloric acid leaching solution of 3 M was employed. Compared to Aliquat 336 (N-Methyl-N, N, N-trioctyl ammonium chloride), extraction with Cyanex 301 (bis(2,4,4-trimethylpentyl) dithiophosphinic acid) led to selective extraction of Cu(II) over other metal ions. Employing ion exchange with TEVA-SCN resin can completely separate Co(II) over Mn(II). After adjusting the pH of Co(II) free raffinate to 3, Mn(II) was quantitatively extracted by the mixture of Alamine 336 (mixture of tri-octyl/decyl amine) and PC 88A (2-ethylhexyl hydrogen-2-ethylhexylphosphonate) with two stage cross-current extraction. The synthesized ionic liquid (ALi-CY) was used for complete extraction of Ni(II), whereas Li(I) remained in final raffinate. The metal ions in the loaded organic phase were completely stripped with the proper agents (5% aqua regia for Cu(II), 5% NH3 for Co(II), weak H2SO4 solution for Mn(II) and Ni(II) stripping, respectively). The experimental results revealed that purity of the metal ions in stripping solution was higher than 99.9%. A flowsheet was suggested to separate metal ions from the HCl leaching solutions of spent LIBs.