Ionic Liquid Extractants in Molecular Diluents: Extraction Behavior of Plutonium (IV) in 1,3-Diketonate Ionic Liquids

Abstract

Room temperature ionic liquids (RTILs) containing β-diketonate anions have been prepared and studied for the extraction of ²³⁹Pu(IV), ²³³U(VI), and ²⁴¹Am(III) from nitric acid medium. The ionic liquids such as alkylquaternaryammonium thenoyltrifluoroacetonate (R₄NTTA), and 1-alkyl-3-methylimidazolium thenoyltrifluoroacetonate (amimTTA), with methyl, butyl, hexyl, heptyl, and octyl moieties have been prepared and characterized by ¹H and ¹³C nmr and IR spectroscopy. The distribution ratio of plutonium(IV) (D _Pu(IV)) in a solution of tri-n-octylmethylammonium thenoyltrifluoroacetonate (TOMATTA) present in tri-n-octylmethylammonium bis(trifluoromethylsulfonyl)imide (TOMANTf₂) and amimTTA in amimNTf₂ was studied as a function of various parameters. The unique property of β-diketonate ionic liquids, namely, the miscibility in molecular diluents, was exploited to elucidate the mechanism of Pu(IV) extraction in these ionic liquids.