Selective extraction of Al ³⁺ from the leaching solution of cathode materials of spent ternary lithium‐ion batteries by using <scp>D2EHPA</scp> ‐ <scp>TBP</scp> ‐kerosene

Abstract 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.