Diglycolamide-functionalized task specific ionic liquids for nuclear waste remediation: extraction, luminescence, theoretical and EPR investigations

Abstract

A 3.6 × 10⁻² M solution of a diglycolamide-functionalized task specific ionic liquid (DGA-TSIL) in [C₄mim][NTf₂] was used for the extraction of actinides (mainly Am) and other elements present in high level nuclear waste. The extraction of Eu³⁺ was relatively higher than that of Am³⁺ conforming to the mechanism displayed by other diglycolamide extractants such as TODGA (tetraoctyl diglycolamide). The distribution ratio values decreased in the presence of simulated high level waste (SHLW) as compared to those obtained with pure tracers. The nature of the extracted species was established by the slope analysis method which suggested 1 : 2 species for the extraction of Am³⁺ and Eu³⁺. Calculation of the Judd–Ofelt parameters from the luminescence data of the Eu³⁺ complexes indicated that the structure of the extracted complexes exhibits S₄ symmetry. Theoretical calculations showed virtually no difference between the structures of the complexes of Am³⁺ and Eu³⁺. The nature of the radiolytic degradation products was analyzed by electron paramagnetic resonance (EPR) spectroscopic measurements revealing the presence of alkyl imidazolium and methyl radicals.