γ-ray-induced radiolysis of CMPO/[C2mim][NTf2] and its effect on Eu3+ extraction

Abstract

The γ-radiolysis of octylphenyl-(N,N-(diisobutyl)carbamoyl-methyl) phosphine oxide (CMPO) in 1- ethyl-3-methylimidazoliumbis (trifluoromethylsulfonyl) imide ([C2mim][NTf2]) was studied. The effect of radiation on CMPO/[C2mim][NTf2] extractability was also investigated. Quantitative analysis of CMPO in irradiated CMPO/[C2mim][NTf2] systems, identification and semi-quantitative analysis of the radiolytic products were performed using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS). For comparison, CMPO/dodecane was also studied under the same conditions. The radiolysis ratio of CMPO in [C2mim][NTf2] was found to be lower than in dodecane, because of the different radiolysis pathways. The radiolysis pathway of CMPO in molecular solvent was mainly chain scission of C―P and C―N, while that in [C2mim][NTf2] was the elimination of isobutyl, as well as substitution reactions with [C2mim]+● and •CF3 generated from solvent [C2mim][NTf2]. Based on the radiolysis study, we propose a radiolysis pathway for CMPO/[C2mim] [NTf2], providing a deeper understanding of the radiolytic mechanism of CMPO in ionic liquids. Finally, the Eu3+ partitioning of CMPO/[C2mim][NTf2] from 0.01 mol∙L−1 HNO3 was higher than 99% at 800 kGy.