Synergistic Effect between Bifunctional Ionic Liquids and a Molecular Extractant for Lanthanide Separation

A novel form of synergistic extraction using both ionic liquid extractants and a molecular extractant is reported. The molecular extractant (TRPO, a mixture of four trialkylphosphine oxides) and anion precursors of the ionic liquid extractants (HDEHP and HEH[EHP]) are the most commonly used industrial extractants for f-block element separation. Development of acid–base coupling bifunctional ionic liquids (ABC-BILs) for rare earth elements (REEs) separation offers a promising strategy to reduce the millions of tons of industrial saponification wastewater that are produced annually. The synergistic effects of the ABC-BILs with TRPO contributed to increased extractabilities and selectivities of middle and heavy lanthanides, revealing theoretical importance and engineering potential in REEs separation.