New hydrophobic DES based on tri–n-octylphosphine oxide and dicarboxylic acids: synthesis, spectroscopy and liquid–liquid extraction of actinides

A search is initiated for new solvents for liquid–liquid extraction (LLE) chemistry of actinides for future separations. Of late, reports on deep eutectic solvents (DES), which resemble ionic liquids, are on the rise. Two hydrophobic DES based on tri– n -octylphosphine oxide (TOPO) and simple dicarboxylic acids, namely, oxalic acid and its higher homologue, malonic acid are prepared and characterized by FT-IR, UV–Vis, water content, density and viscosity measurements. The LLE chemistry of U(VI) and Am(III) is carried out using the above DES as a function of a few parameters and UV–Vis and IR spectra of the extracted phases were also recorded. The results are discussed with appropriate explanations in this report.