Lithium isotopes separation by using benzo-15-crown-5 in eco-friendly extraction system

A green and efficient liquid–liquid extraction system was developed for the separation of lithium isotopes by using hydrophobic ionic liquids (ILs   =   [C 4,6,8,10 mim] + [NTf 2 ] − ) as extraction organic phase and benzo-15-crown-5 (B15C5) as complexing agent. The maximum single-stage separation factor α of 6 Li/ 7 Li obtained in this study was 1.029   ±   0.001, indicating 6 Li was enriched in ionic liquid phase while 7 Li was concentrated in the aqueous phase. The lithium ion was extracted into the ionic liquid in the formation of 1:2 complex [Li + (B15C5) 2 ]. The negative data of thermodynamic parameters (∆   H 0 and ∆   G 0 ) suggest that the extraction system was a spontaneous exothermic process . In addition, effective lithium isotopes separation factor and the extraction efficiency of lithium ions can be gained in the condition of lower temperature with softer counter anions in the novel extraction system.