Green separation and recovery of cobalt and nickel from sulphuric acid achieved by complexation-assisted solvent extraction

Ternary cathodes account for more than half of the Lithium-Ion Batteries (LIBs) cathode market share and their recycling draws the most attention. Solvent extraction is the most efficient and common method to separate and recover Co and Ni from spent ternary cathode leachates. However, the traditional extraction process produces a large amount of saline wastewater, thus will seriously pollute the environment. In this work, an environmental approach is proposed by adding a water-soluble complexing agent into the aqueous phase, the separation factor is 2 times higher and the consumption of NaOH is 90% reduced compared to the Na-saponified counterpart, which was attributed to the differences of the complexation between metal ions and complexing agent in aqueous phase. The differences in the complexing ability are enhanced with an increased local nucleophilicity index of the active sites along with a reduced molecular volume in complexing agent, thus leading to superior cobalt extraction efficiency (∼98.9%) and separation factor (∼345). In addition, because of the fact that the whole-process pollution control is needed for cleaner chemical production, a green process is developed by recovering additives through Tri-n-butyphosphate. This excellent separation performance suggests that adding complexing agent in solvometallurgical recovery process may aid in the future development of high-purity raw metals for advanced fields.