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

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][NTf 2 ] as organic phase with solvent extraction method . The key factors such as anions of lithium salts, concentrations of LiNTf 2 , initial pH values of aqueous phase, solvents, volume ratio of dichloromethane and [BMIm][NTf 2 ] 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 6 Li and 7 Li 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 6 Li and 7 Li exchange reaction were calculated by data obtained on temperature during experiments, which explained that the exchange behavior of 6 Li and 7 Li in this system was a spontaneous exothermic reaction . In addition, this system was able to efficiently separate lithium isotopes at lower temperature.