Electromigration separation of lithium isotopes with B12C4, B15C5 and B18C6 systems

Abstract

High abundance ⁶Li and ⁷Li are essential materials for the nuclear industry. In this article, the lithium isotope separation effect and lithium-ion transport of a “lithium salt aqueous solution (anolyte)|crown ethers–ionic liquid organic solution|ammonium chloride aqueous solution (catholyte)” electromigration system with B12C4, B15C5 and B18C6 as phase transfer catalysts were investigated systematically. The results show that separation factors can reach 1.028 (B12C4), 1.024 (B15C5) and 1.011 (B18C6), respectively, when LiCl solution is used as the anolyte. The separation effect mainly originated from interfaces between anolytes and organic solutions, and was less affected by an electric field. The separation effect between organic solution and catholytes was greatly affected by the electric field for B12C4 and B15C5 systems, which converted from ⁷Li-enrichment to ⁶Li-enrichment with increased voltage. For the B18C6 system it was less affected. Furthermore, lithium ion transport in B12C4, B15C5 and B18C6 systems was greatly promoted by the electric field, with the Li⁺ concentration in catholytes of B12C4, B15C5 and B18C6 systems increased from 0.088 mg L⁻¹, 0.286 mg L⁻¹ and 0.778 mg L⁻¹ to 8.321 mg L⁻¹, 7.422 mg L⁻¹ and 4.631 mg L⁻¹ respectively as the voltage increased from 2 V to 16 V. The B12C4 system has been confirmed as the optimal solution considering both the Li⁺ transport and isotope separation effect.