Selective recovery of transition metals from spent lithium-ion batteries leachate with Ni synergistic extraction system

Recycling spent lithium-ion batteries (LIBs) can not only generate ecological benefits but also realize low-carbon energy transition. Here, comprehensive recovery of transition metals from spent LIBs leachate using nickel (Ni) synergistic extraction system has been proposed. It was discovered that the combination of HEH(EH)P and Cyanex301 showed a strong synergistic extraction effect on Ni²⁺ and could also achieve the co-extraction of Ni²⁺, Co²⁺, Mn²⁺ after examining the extraction effects of single and mixed extractants of HEH(EH)P and Cyanex301. The mechanism of synergistic extraction of Ni²⁺ with mixed extractants was elucidate according to the slope analysis, FT-IR spectrometry and NMR spectrometry results. Then through a three stages of counter-current extraction process with 1.5 mol/L mixed extractant (X_HEH(EH)P = 0.7, HEH(EH)P saponification degree of 60 %) and two stages of scrubbing process with 0.05 mol/L H₂SO₄, 99.18 % of Ni²⁺, 99.02 % of Co²⁺ and 99.93 % of Mn²⁺ were comprehensively recovered, while only 0.27 % of Li⁺ were lost. The Ni²⁺, Co²⁺, and Mn²⁺ loaded in the organic phase were entirely removed by a three stages of counter-current stripping process with HCl under O/A = 2.5/1. The synergistic extraction system still demonstrated outstanding reusability even after five cycles.