Toward Radiation-Resistant Ionic Liquids. Radiation Stability of Sulfonyl Imide Anions

Abstract

Room-temperature hydrophobic ionic liquids (ILs) are considered for processing of spent nuclear fuel, including as possible replacements for molecular diluents in liquid-liquid extraction. This application requires radiation stability of the constituent ions. Previous research indicated that most of the anions that are currently used in the synthesis of ILs are prone to fragmentation under prolonged radiation exposure, which causes deterioration of the corresponding ILs. An exception to this general rule is phthalimide; unfortunately, this anion is too basic to be useful for extraction solvents, as these separations involve acidic conditions. The acidity of the imide can be increased by replacing the carbonyl groups by sulfonyl groups, which incidentally transform these imides into familiar artificial sweeteners such as saccharin. In the present study, we use electron paramagnetic resonance spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometry to assess the radiation stability of ILs based on such "sweet" sulfonyl imide anions. Our results suggest that saccharinate and o-benzenedisulfonimide are remarkably stable to radiation-induced fragmentation.

Extraction of uranium(VI) from nitric acid solutions using N,N-dihexyloctanamide in ionic liquids: Solvent extraction and spectroscopic studies

“…Allen et al, [41] reported poor stability of the RTIL based solvents, while some recent reports indicate reasonably good stability of these solvent systems if properly designed. [42] The present studies indicated two interesting features. Firstly, the extraction of the metal ion showed marginal increase with the dose when the solvent system did not contain DHOA and the amount of U extracted was insignificant in all the cases.…”

Polymerization of Room-Temperature Ionic Liquid Monomers by Electron Beam Irradiation with the Aim of Fabricating Three-Dimensional Micropolymer/Nanopolymer Structures

“…17 The reactive species indicated here are solvated electrons and radical ions. The mechanism for the formation of these species has widely been studied by many radiation chemists.…”

The First Lithium-ion Battery with Ionic Liquid Electrolyte Demonstrated in Extreme Environment of Space

“…Shkrob et al have reported the radiation stability of ionic liquids with reference to their application to nuclear fuel processing. [41][42][43] Sulfonyl imide anions typified by bis(trifluoromethylsulfonyl)imide, whose structure contains SO 2 N É , can be easily oxidized through production of an imidyl radical (CF 3 SO 2 N•), which usually involves chain radiolysis of ionic liquids. 41,42 An irreversible radiolytic reaction of alkylated ammonium cations (and perhaps other aliphatic cations) can occur through elimination of their alkyl chain in a high-dose environment.…”

“…[41][42][43] Sulfonyl imide anions typified by bis(trifluoromethylsulfonyl)imide, whose structure contains SO 2 N É , can be easily oxidized through production of an imidyl radical (CF 3 SO 2 N•), which usually involves chain radiolysis of ionic liquids. 41,42 An irreversible radiolytic reaction of alkylated ammonium cations (and perhaps other aliphatic cations) can occur through elimination of their alkyl chain in a high-dose environment. 41 Even alkylated imidazolium cations, one of the typical aromatic cations comprising many ionic liquids, can decompose radiolytically via several degradation pathways.…”