Lithium isotope separation using 4′-acetylbenzo-15-crown-5 and 1-butyl-3-methylimidazolium bis[(trifluoromethyl) sulfonyl] imide in the synergistic extraction system

Abstract A novel synergistic extraction system was studied for the separation of lithium isotopes using lithium salts solution as aqueous phase and dichloromethane containing 4′-acetylbenzo-15-crown-5 and [BMIm][NTf2] as organic phase with solvent extraction method. The key factors such as anions of lithium salts, concentrations of LiNTf2, initial pH values of aqueous phase, solvents, volume ratio of dichloromethane and [BMIm][NTf2] were investigated in this study. Results showed that the maximum extraction rate of lithium was 68.36% and the maximum single stage separation factor of 6Li and 7Li was 1.056 ± 0.002. The formed complex in organic phase was studied by the slope analysis method, which indicated that the complex was composed of Li-ion and 4′-actylbenzo-15-crown-5 by 1:1. The thermodynamic parameters of the 6Li and 7Li exchange reaction were calculated by data obtained on temperature during experiments, which explained that the exchange behavior of 6Li and 7Li in this system was a spontaneous exothermic reaction. In addition, this system was able to efficiently separate lithium isotopes at lower temperature.