α-Radiolysis of ionic liquid irradiated with helium ion beam and the influence of radiolytic products on Dy3+ extraction

Abstract

Helium ion (He⁺) beam produced by a heavy ion linear accelerator was used to simulate α-rays for studying the radiation effect on 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid ([C₄mim][NTf₂]). The water-soluble radiolytic products of [C₄mim][NTf₂] under He⁺ beam irradiation were analysed, and it was found that they were similar to those by γ-ray irradiation, but their amount was much less than that by γ-ray irradiation, which was attributed to the recombination of [C₄mim][NTf₂] radical cations in track by high linear energy transfer (LET) radiations of the He⁺ beam. The extracting behaviour of Dy³⁺ using irradiated [C₄mim][NTf₂] in combination with alkylated bis-triazinyl-pyridine (CA-BTP) was assessed, and found that the influence of He⁺ beam on the extraction was less than that of γ-ray irradiation. In addition, radiolytic products have a different influence on Dy³⁺ extraction at different doses; Dy³⁺ partitioning decreases at 50 kGy due to the protonation of CA-BTP and the inhibition of cation exchange mechanism by radiation-formed hydrogen ions. The abnormal increase of Dy³⁺ partitioning at 100 kGy is mainly attributed to the precipitation formed between Dy³⁺ and radiolytic products (F⁻ and SO₃²⁻).