Selective lithium extraction from magnesium‐rich brines using deep eutectic solvents: Multiscale molecular insights

Abstract This study proposes a novel strategy for Li + extraction from high Mg 2+ /Li + brines using deep eutectic solvent (DES)‐based extractant, including L‐carnitine hydrochloride (LCH) as a hydrogen bond donor (HBD), FeCl 3 as a hydrogen bond acceptor (HBA), and tributyl phosphate (TBP) as a ligand. This system achieves superior Li + extraction efficiency (94.5%) and Li + /Mg 2+ selectivity (399), outperforming most traditional solvents. Multidimensional spectroscopy confirms a complex structure of Li + ·3TBP·FeCl 4 − . Combining quantum chemical (QC) calculations and molecular dynamics (MD) simulations, the Li + extraction mechanism at the multi‐scale molecular level was elucidated. Dechlorinated LCH + was proven to weaken the Li + solvation shell via hydrogen bonding (HB) network (O–H⋯O) by carboxyl group. FeCl 4 − (Cl − acceptor) interacts with TBP, creating molecular channels for Li + transport and establishing multiple interactions (Li + ⋯Cl–Fe, Li + → OP, etc.) to facilitate the Li + migration to the organic phase. This study aims to provide theoretical guidance and new insights for high‐efficiency DES design in Li + extraction.