Selective Separation of Lithium, Magnesium and Calcium using 4‐Phosphoryl Pyrazolones as pH‐Regulated Receptors

Abstract Ensuring continuous and sustainable lithium supply requires the development of highly efficient separation processes such as LLE (liquid‐liquid extraction) for both primary sources and certain waste streams. In this work, 4‐phosphoryl pyrazolones are used in an efficient pH‐controlled stepwise separation of Li + from Ca 2+ , Mg 2+ , Na + and K + . The factors affecting LLE process, such as the substitution pattern of the extractant, diluent/water distribution, co‐ligand, pH, and speciation of the metal complexes involved, were systematically investigated. The maximum extraction efficiency of Li + at pH 6.0 was 94 % when Mg 2+ and Ca 2+ were previously separated at pH<5.0, proving that the separation of these ions is possible by simply modulating the pH of the aqueous phase. Our study points a way to separation of lithium from acid brine or from spent lithium ion battery leaching solutions, which supports the future supply of lithium in a more environmentally friendly and sustainable manner.