Hydrophobic Deep Eutectic Solvents Incorporating Trioctylphosphine Oxide: Advanced Liquid Extractants

A low viscosity, hydrophobic eutectic solvent based on trioctylphosphine oxide (TOPO) has been developed and characterized, and its use as an extractant demonstrated for liquid–liquid separation of uranyl nitrate from aqueous acid. This strategy of liquefying the active extracting agent as a eutectic liquid produced liquids that contain an intrinsically high concentration of TOPO (ca. 80 wt %, 1.875 mol L–1 at χTOPO = 0.50) and renders the use of an organic (hydrocarbon) diluent redundant.