Solvent extraction for lithium isotope separation by 4-NO2-B15C5/[BMIm][NTf2] system

Abstract

The evolution of the nuclear industry is inextricably linked to lithium isotopes. With its distinct benefits, the solvent extraction approach is projected to achieve industrial separation of lithium isotopes. However, the lack of studies on the extraction process conditions and mechanisms has limited the development of multi-stage processes. In this paper, based on the 4-NO2-B15C5/[BMIm][NTf2] system, the process conditions and extraction mechanism of the system were investigated by thermodynamic and kinetic studies. The results indicate that lithium isotope separation is a spontaneous exothermic process controlled by diffusion. In addition, DFT calculations show that the binding sites of crown ether and Li+ are located in the coronary heart of crown ether, and electrostatic and van der Waals forces mainly exist between them. On this basis, a 10-stage cross-flow extraction experiment was carried out using crown ether as the extractant. The aqueous phase feed solution is fully utilized, and the 7Li abundance is increased to 93.29 %. In summary, this research provides a foundation for the development of synergistic multi-stage extraction techniques in the future.