Lithium isotope separation by crown ethers of different nitrogen-containing derivatives in the ionic liquid-anisole system

A green and efficient ionic liquid-anisole extraction system was employed for the separation of lithium isotopes by comparing 4‑aminobenzo‑15‑crown‑5 (4‑NH 2 ‑B15C5), 4‑nitrobenzo‑15‑crown‑5 (4‑NO 2 ‑B15C5) and benzo‑15‑crown‑5 (B15C5) extraction agents. The results of the effects of crown ether substituents, crown ether concentration and lithium salt anion on solvent extraction indicated that the molar ratio of crown ether and lithium ion complex is 2:1 and the order of the extraction efficiency in three extraction agents was 4‑NH 2 ‑B15C5 >  B15C5  > 4‑NO 2 ‑B15C5. Furthermore, the single-stage separation factor α for 6 Li/ 7 Li obtained in present work was 1.032 and maximum abundance of 6 Li in organic phase was reached 7.762% in the extraction system of LiI/4‑NO 2 ‑B15C5‑ILs.