Liquid-liquid extraction separation of lithium isotopes by using room-temperature ionic liquids-chloroform mixed solvent system contained benzo-15-crown-5

A novel liquid-liquid extraction system was investigated for the selective separation of lithium isotopes using ionic liquids.(ILs = [C(6,8,10,12)mim](+)[PF6](-)) as extraction solvent and benzo-15-crown-5 (B15C5) as extractant. The effects of the concentration of lithium salt, counter anion of lithium salt, initial pH of aqueous phase, and extraction temperature on the lithium isotopes separation were studied. The maximum single-stage separation factor alpha of Li-6/Li-7 obtained in the present study was 1.038 +/- 0.002, indicating the lighter isotope Li-6 was enriched in organic phase while the heavier isotope Li-7 was concentrated in the aqueous phase. The formation of 2:1 complex Li(B15C5)(2)(+) in the IL phase was determined on the basis of slope analysis method. The large value of the free energy change (-G(0) = 77.87J mol(-1)) indicated the high separation capability of the lithium isotopes by B15C5/30%CH3Cl-70% C(6)mimPF(6) mixture extraction system. Lithium in Li(B15C5)(2)(+) complex was stripped by 0.5 mol center dot L-1 HCl solution. The extraction system offers high efficiency, simplicity application prospect to separation lithium isotope separation from LiCl solution. (c) 2016 Elsevier B.V. All rights reserved.