A novel polyvinyl alcohol (PVA) grafted 4'-formoxylbenzo-15-crown-5-ether (FB15C5) (PVA-g-FB15C5) for lithium isotopes separation was prepared from PVA and FB15C5 as starting materials via acetalization reaction.The effects of the reaction conditions such as catalyst content (A)

crown ether content (B) and PVA concentration (c) on immobilization amount of crown ether were investigated using the response surface method.The results showed that the immobilization amount of crown ether obtained under the optimum conditions of catalyst content of 0.79 g

crown ether content of 0.51 g and PVA concentration of 3.7104 mg/L was 2.11 mmol/g.Further

the single stage separation factor for lithium isotopes increased with an increase in the softness of counter anion in lithium salts during the solid-liquid extraction for lithium isotopes separation via PVA-g-FB15C5 with the immobilization amount of crown ether of 2.11 mmol/g.Moreover

the maximum value of single stage separation factor obtained by PVA-g-FB15C5 was 1.039 when LiBr aqueous solution was used as an extraction solution at 20 ℃.It was also found that the heavier isotope -7Li was enriched in the polymer phase during the process of solid-liquid extraction

whereas the lighter one -6Li was concentrated in the solution phase.