Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions with Mixtures of Diphenyl-N,N-dioctylcarbamoylmethylphosphine Oxide and Lithium Bis[(trifluoromethyl)sulfonyl]imide

The extraction of U(VI), Th(IV), and lanthanide(III) ions with mixtures of diphenyl-N,N-dioctylcarbamoylmethylphosphine oxide (Ph₂Oct₂) and lithium bis[(trifluoromethyl)sulfonyl]imide (LiTf₂N) in dodecane containing 10% octanol was studied. A synergistic effect was discovered during the extraction of metal ions with such mixtures. When extracting Ln(III) from solutions of 3 M HNO₃, the D_Ln values in the system with Ph₂Oct₂–LiTf₂N are more than three orders of magnitude higher than when extracting with a solution of Ph₂Oct₂. The stoichiometry of the extracted complexes was determined, and the effect of HNO₃ concentration on the extraction of metal ions was studied. It has been established that actinide and lanthanide(III) ions are extracted with a mixture of Ph₂Oct₂ and LiTf₂N from nitric acid solutions via a cation-exchange mechanism.