Extraction Separation of Lithium Isotopes by Using XAD-7 Resins Impregnated With Ionic Liquid and Benzo-15-Crown-5

Imidazolium-type ionic liquid (［C₈mim］［BF₄］, ［C₈mim］［PF₆］ and ［C₈mim］［(SO₂CF₃)₂N］) and benzo-15-crown-5 were immobilized on XAD-7 resin to obtain the impregnated resin for lithium isotopes separation. IR and SEM characterizations of the impregnated resins indicate that ionic liquids and benzo-15-crown-5 are immobilized in the resins successfully and the thermal analysis indicates that the materials are thermally stable. The optimum E was obtained in the initial solution at pH=5.55. The larger extraction percentages and separation factors values were obtained from LiSCN solution and CF₃COOLi solution, respectively. The maximum single-stage isotopes separation factor of ⁶Li/⁷Li is up to 1.045±0.002. The equilibrium time of extraction is attained in 2.5-3 h. The thermodynamic parameters of the system were presented and revealed that the extraction reaction was a spontaneous process and the temperature had slight influence on the extraction separation of lithium isotopes. The mechanism of extraction system show that ⁶Li enriches in the solid phase and ⁷Li concentrates in the aqueous phase. The impregnated resins can be regenerated and reused for lithium isotopes separation.