A green hydrometallurgical route is reported for recovering cobalt and copper from end of life lithium ion batteries by coupling mild sulfuric acid leaching with aqueous two phase systems. Multivariate methodologies were used to determine the optimal leaching conditions, namely 3.00 M acid, 86.6 °C, 120 min, a solid to liquid ratio of 135 g·L⁻¹, and 10.8% v/v H₂O₂, delivering leaching efficiencies that exceeded those obtained under harsh condition protocols. The two phase system was induced directly from the sulfate leachate by adding polyethylene glycol, eliminating the need for additional salting-out agents and simplifying the overall separation process. The water rich lower phase was identified as the metal enriched phase. Screening of low toxicity extractants showed that only 8 hydroxyquinoline and chloride significantly increased copper extraction. Raising 8 hydroxyquinoline concentration and pH further enhanced copper extraction, consistent with the higher stability of the Cu–8 hydroxyquinoline complex relative to its cobalt analogue. Sequential extractions (five stages) increased the extraction percentage to 27.6±0.7 for cobalt and 89.0±4.0 for copper. Subsequent stripping transferred 40.1±0.9% of cobalt and 95.2±4.2% of copper, yielding an aqueous strip containing 82.0% cobalt and 11.1% copper. Overall, the integrated route combines efficiency and selectivity with reduced reagent and energy demands, offering a scalable, lower impact pathway for lithium ion battery recycling and highlighting the potential of aqueous two phase systems as an environmentally benign alternative to conventional solvent extraction processes.
Silva et al. (Fri,) studied this question.