The selective complexation of crown ethers for lithium isotope separation: A critical review

Nuclear energy is considered as the ultimate solution for future energy needs. High-purity lithium isotopes (6Li and 7Li) serve as the foundation raw materials for nuclear reactions. The development of environmentally friendly and efficient lithium isotope separation technologies plays an irreplaceable role in nuclear energy. Utilizing crown ethers for the selective complexation of metal ions has been proven to be a highly promising method for lithium isotope separation. In this review, various lithium isotope separation methods based on crown ether chemistry, including liquid–liquid extraction, solid–liquid adsorption, ion-exchange chromatography, membrane adsorption, and membrane chromatography techniques are introduced. The technologies coupling crown ethers with other separation methods, such as ionic liquid extraction and electric field migration, are summarized. The principles underlying lithium isotope separation are discussed from various perspectives. Finally, the current challenges and issues in lithium isotope separation research are described, and the future prospects for utilizing crown ethers in lithium isotope separation are outlined. To sum up, the review provides insights on crown ether chemistry and relative technologies for industrial-scale lithium isotopic enrichment in future nuclear energy research.