Separation of lithium isotopes by using solvent extraction system of crown ether-ionic liquid

摘要

A solvent extraction system was selected to separate lithium isotopes by using 1-Ethyl-3-methyl-imidazolium-bis (trifluoromethysulfonyl)-imide ([EMIm][NTf2]) as extraction solvent, Dibenzo-15-crown-5 (DB15C5) as extracting agent and a traditional organic solvent as diluent. The effect of kinds of diluent, the content of ionic liquid in organic solvent, extraction time, extractant concentration and counter anions of lithium salt on the separation of lithium isotopes was studied. The single-stage separation factor a can reach up to 1.031 +/- 0.001 and the abundance of the light isotope Li-6 in organic phase can reach 7.76%. The exchange mechanism between the lithium salt and the ionic liquid is cation exchange. Lithium ions and ionic liquid cations are 1:1 exchange in the extraction system. Multistage experiment for separation of lithium isotope was also developed for enrichment of Li-6 as much as possible. The abundance of Li-6 in organic phase can reach 7.80% after 5 stages extraction experiment. Lithium of organic phase was stripped into the aqueous phase by 1 mol L-1 HCl solution.