Synergism in the Solvent Extraction of Europium(III) with Thenoyltrifluoroacetone and CMPO in Methylimidazolium Ionic Liquids

The solvent extraction of Eu(III) from an aqueous chloride phase into hydrophobic ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides ([C(1)C(n)im(+)][Tf2N-], n=4, 6, 8 and 10), by -diketone 2-thenoyltrifluoroacetone (HTTA) alone and in combination with N,N-diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO) was investigated. The interaction between the two extractants (acidic/neutral) in deuterochloroform has been studied by H-1, C-13, F-19 and P-31 NMR spectra and NOESY experiments. H-1 and F-19 Q-NMR analytical techniques were also applied for determination of [C(1)C(4)im(+)] and [Tf2N-] entities transferred into the aqueous phase. Eu(III) was efficiently extracted by HTTA/[C(1)C(n)im(+)][Tf2N-] and HTTA/CMPO/[C(1)C(n)im(+)][Tf2N-] systems but a relatively small synergism was established. A cation extraction mechanism was proposed via the log-log slope analysis method. The effect of the IL cation alkyl chain length on the extraction process was studied as well.