Extraction of Actinides and Lanthanides from Nitric Acid Solutions with Mixtures of 1,5-N,N'-Bis[(Diphenylphosphoryl)Acetyl(Hexyl)Amino]pentane and New Asymmetrical Phosphonium- and Imidazolium-Based Ionic Liquid

A new dicationic ionic liquid, 1-methyl-3-(4-(tributylphosphonio)butyl)-1H-imidazol-3-ium di[bis(trifluoromethanesulfonyl)imide] [ImP][Tf₂N]₂, showing high hydrophobicity (solubility in water is 9.2 × 10^–4 mol/L) has been synthesized. The extraction of U(VI), Th(IV), and lanthanides(III) from nitric acid solutions with mixtures of 1,5-N,N'-bis[(diphenylphosphoryl)acetyl(hexyl)amino]pentane (L) containing two bidentate Ph₂P(O)CH₂C(O)N(Hex)- fragments connected by pentamethylene spacer through amide nitrogen atoms and [ImP][Tf₂N]₂ in 1,2-dichloroethane (DCE) has been studied. During the extraction of metal ions in this system, a significant synergistic effect has been observed. The influence of the composition of aqueous and organic phases on the efficiency of metal ions extraction into organic phase has been considered and the stoichiometry of extracted complexes has been determined. The synergistic effect in the extraction of Ln(III) from 3 M HNO₃ solutions with a mixture of L and [ImP][Tf₂N]₂ in DCE is an order of magnitude higher than in the L–[C₈mim][Tf₂N]–DCE system.