Lithium extraction from salt‐lake brines using dicationic ionic liquids: <scp>ePC</scp>‐<scp>SAFT</scp> modeling and molecular mechanisms

Abstract This work proposes a novel strategy for enhancing Li + extraction from salt‐lake brines with the high Mg 2+ /Li + ratio using dicationic ionic liquid (DIL)‐based extractants. The ternary mixture of the DIL [DOMIM][Tf 2 N] 2 , tributyl phosphate (TBP), and dichloromethane (DCM) as a diluent achieved a higher single‐stage Li + extraction efficiency (86.40%) and separation selectivity of Li + /Mg 2+ (302.37) compared with the ternary mixture based on monocationic IL [OMIM][Tf 2 N] instead of the DIL. The high Li + extraction performance could be maintained over five‐cycle regeneration. Electrolyte perturbed‐chain statistical associating fluid theory was used to qualitatively predict activity coefficients of Li + and Mg 2+ in the organic phase of the so‐called “organic–inorganic complex strong electrolyte system.” The DIL‐enhanced extraction mechanisms at the molecular level (i.e., Li + extracted the form of 2Li + + 3TBP + 2[Tf 2 N] − complex) was revealed by slope analysis spectrum characters and quantum chemical calculations. This study provides guidance for the rational design of new IL‐based extractants for high‐efficiency Li + extraction from brines.