Radiolysis of crown ether–ionic liquid systems: identification of radiolytic products and their effect on the removal of Sr2+ from nitric acid

Abstract

The quantitative analysis and identification of the radiolytic products of dicyclohexano-18-crown-6 (DCH18C6), 4′,4′′(5′′)-di-tert-butyldicyclohexano-18-crown-6 (DtBuCH18C6) and benzo-18-crown-6 (B18C6) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C₄mim][NTf₂]) ionic liquid after irradiation were performed for the first time. It was found that the yield for radiolytic destruction of DCH18C6 and DtBuCH18C6 was less than that for B18C6. The main radiolytic products were identified as substituted crown ethers formed between crown ether and active radicals such as methyl, trifluoromethyl, butyl, and [C₄mim]˙ radicals generated during the irradiation of the crown ether–[C₄mim][NTf₂] system. The radiation effect on the Sr²⁺ partitioning of the crown ether–[C₄mim][NTf₂] system shows further that DCH18C6–[C₄mim][NTf₂] and DtBuCH18C6–[C₄mim][NTf₂] still have good extractability for Sr²⁺ after irradiation. The extraction ability of DCH18C6–[C₄mim][NTf₂] and DtBuCH18C6–[C₄mim][NTf₂] system for Sr²⁺ decreased by 14.4% and 18.2% even at 500 kGy, respectively.