Preferentially selective lithium recovery from spent lithium-ion battery leachates using NaBPh4/TBP synergistic extraction

Preferential Li extraction was achieved from spent lithium-ion battery leachates. • Complete separation of Li from Ni, Co, and Mn was achieved. • NaBPh₄ and TBP exhibit a significant synergistic effect on Li extraction. • The organic phase achieved 98.3% Li extraction via five-stage extraction. • Li in the stripped solutions was precipitated as pure Li 3 PO 4 . Effective recycling of spent lithium-ion batteries (LIBs) is vital for metal recovery. However, poor lithium (Li) purity and recovery efficiency highlight the need to develop new extractants for preferential Li recovery. In this work, a synergistic solvent extraction system consisting of sodium tetraphenylborate (NaBPh₄), tributyl phosphate (TBP) and 2-octanone was developed for the selective extraction of Li + from pretreated spent LIB leachates containing Li + , Ni 2+ , Co 2+ and Mn 2+ . Key operating parameters including initial Li + concentration, solution pH value, NaBPh 4 -to-Li + molar ratio, TBP volume fraction, organic-to-aqueous (O/A) volume ratio, and extraction time were systematically investigated. Under the optimized conditions, a five-stage extraction achieved a total Li + recovery of 98.3%. The loaded Li + in the organic phase was completely stripped using 0.5 mol/L HCl at an O/A volume ratio of 0.5, with a stripping efficiency of 100%. The stripped organic phase could be regenerated by supplementing NaBPh₄ at an optimal molar ratio n(NaBPh₄)/n(Li + ) = 5.5. FTIR and slope analysis revealed a distinct synergistic mechanism: NaBPh₄ initially combines with TBP to form a [(NaBPh₄)(TBP)] adduct, followed by ion exchange between Li + and Na + to generate [(LiBPh₄)(TBP)]. The prominent steric hindrance of NaBPh₄ effectively suppressed the co-extraction of Ni 2+ , Co 2+ and Mn 2+ , enabling outstanding Li + selectivity. Finally, Li + was recovered as Li₃PO₄ with 99.9% purity and 98.6% yield, whereas the raffinate containing Ni 2+ , Co 2+ , and Mn 2+ was suitable for producing ternary precursor materials. This work presents a simplified and sustainable “Li-first” strategy with strong potential for efficient and selective metal recovery from spent LIBs. Download: Download high-res image (126KB) Download: Download full-size image