Ionic liquid extractants in molecular diluents: Extraction behavior of europium (III) in quarternary ammonium-based ionic liquids

The ionic liquids, tri-n-octylmethylammonium bis(2-ethylhexyl)phosphate ([A336]+[DEHP]−) and tri-n-octylmethylammonium bis(2-ethylhexyl)diglycolamate ([A336]+[DGA]−) were prepared and characterized by IR and NMR spectroscopy. The extraction behavior of europium (III) in the solution of these ionic liquids present in different molecular diluents was studied as a function of various parameters such as pH, nature of diluent, concentration of ionic liquid. The data obtained were compared with those obtained in a solution composed of the precursors of ionic liquid. The extraction of europium (III) in [A336]+[DEHP]− and [A336]+[DGA]− ionic liquids showed a strong dependence on the nature of molecular diluent used. The distribution ratio of Eu(III) increased with increase of pH; at pH > 2, the distribution ratios obtained in ionic liquids were much higher than their precursors. The effect of diethylenetriaminepentaacetic acid (DTPA) on the extraction of Am(III) and Eu(III) at a fixed pH was studied to separate europium (III) from americium (III). Superior extraction of the target metals and excellent separation factors achieved with the use of these ionic liquids in conventional diluents indicates the feasibility of separating lanthanides from actinides.

► Simple and efficient synthesis of Aliquat-336 based ionic liquids.
► Unusual miscibility of [A336]+[DEHP]− and [A336]+[DGA]− in paraffinic diluents.
► Higher distribution ratio of Eu(III) and Am(III) in the ionic liquid.
► Mutual separation of Eu(III) from Am(III) using [A336]+[DEHP]− and [A336]+[DGA].
► Stoichiometry of Eu(III) extraction in ionic liquids.