Lithium Isotope Electromigration Separation in an Ionic Liquid-Crown Ether System: Understanding the Role of Driving Forces

Lithium isotopes (Li-6 and Li-7) play an important role in the nuclear industry. The development of green and efficient separation methods is a top priority for the lithium isotope industry. In this work, an "aqueous solutionlionic liquid-crown ether organic solutionlaqueous solution" system was constructed and used for lithium isotope electromigration separation. The influence and synergy of Li+ diffusion, electromigration, and chelation of crown ether on Li+ migration and isotope separation were investigated, discussed, and verified carefully. The separating laws were summarized. The process and mechanisms of lithium isotope separation were explored preliminarily. The presence of crown ether in organic solution and the introduction of electric field can change the migration ratio and lithium isotope enrichment effect of different parts in the system. The synergy of Li+ diffusion, electromigration, and chelation of crown ether can change the behaviors of Li+ migration and isotope separation significantly. What's more important, the driving forces are not constant but dynamic. The diffusion increased with the increasing concentration gradient among different parts. The chelation decreased with the increasing Li+ concentration in organic solution. The electromigration also changed with the varied chemical speciation of Li+. The results helped in understanding the roles of driving forces more clearly and provided a foundation for developing green and efficient methods for lithium isotope separation.