Selective extraction of Al3+ from the leaching solution of cathode materials of spent ternary lithium-ion batteries by using D2EHPA-TBP-kerosene

An extraction system consisting of di-2-ethylhexyl phosphoric acid (D2EHPA), tributyl phosphate (TBP), and kerosene was developed for selective recovery of aluminium ions from the leaching solution of cathode materials of spent ternary lithium-ion batteries. The proposed system could significantly separate nickel, cobalt, manganese, and lithium ions from aluminium ions in the leachate. A four-stage cross-flow extraction process using D2EHPA-TBP-kerosene with 40% saponification degree could recover 99.48% of Al 3+ at pH of 1.68 and O/A phase ratio of 1:1. After one-stage washing and five-stage stripping processes, a stripping solution containing nearly pure Al 3+ could be obtained. Then, the Al 2 (SO 4 ) 3 ‧ 17H 2 O product was recovered from the stripping solution by the cooling crystallization method with a yield of 92.63% and a purity of 99.32%. The extraction system showed very stable extraction ability during ten consecutive extraction–washing–stripping cycles. Finally, a cation exchange mechanism was explored by using Fourier transform infrared spectroscopy (FT-IR) characterization.