Liquid-liquid extraction of europium(III) in an alkyl ammonium based ionic liquid containing diglycolamic acid

Abstract

A strongly hydrophobic alkylammonium ionic liquid: methyltrioctylammonium bis (trifluoromethanesulfonyl) imide ([N1888][NTf2]) was explored as diluent for the extraction of europium (III) from nitric acid medium using bis(2-ethylhexyl) diglycolamic acid (HDEHDGA) as extractant. The extraction behavior of europium(III) in HDEHDGA/[N1888][NTf2] was investigated as a function of various extraction parameters such as pH, [HDEHDGA]IL, temperature, concentrations of europium(III) ion and nitrate ion in the aqueous phase. The metal-solvate stoichiometry was determined from the slope analysis of extraction and the data suggested the involvement of two extractant molecules for extraction. The extraction trend obtained in HDEHDGA was compared with other acidic extractants namely bis(2-ethylhexyl) phosphoric acid (D2EHPA) and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) present in [N1888][NTf2]. The diluent property of [N1888][NTf2] was also compared with other ionic liquid diluents as well as molecular diluents. The stripping study of europium(III) and the reusability of the ionic liquid phase were also ascertained.