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

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 Ca2+, Mg2+, 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 Mg2+ and Ca2+ were previously separated at pH