Radiation Effect of Carboxyl-Functionalized Task-Specific Ionic Liquids on UO₂²⁺ Removal: Experimental Study with DFT...

Area of Science:

• Nuclear Chemistry
• Materials Science
• Radiochemistry

Background:

• Ionic liquids are promising solvents for nuclear fuel reprocessing.
• Understanding the stability of ionic liquids under radiation is crucial for their application in uranium extraction.

Purpose of the Study:

• To investigate the effects of radiation on 1-carboxymethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([HOOCCH2MIM][NTf2]).
• To evaluate the impact of radiation-induced degradation on the efficiency of UO2^2+ extraction.
• To elucidate the mechanisms behind the observed changes in UO2^2+ partitioning.

Main Methods:

• Experimental study of radiation effects on [HOOCCH2MIM][NTf2] during UO2^2+ extraction.
• Identification of radiolytic products using 19F NMR and high-resolution ESI-MS.
• Density Functional Theory (DFT) validation for complexing reactions and mechanistic insights.

Main Results:

• Radiolytic degradation of both the cation and anion of [HOOCCH2MIM][NTf2] was observed.
• Formation of radiolytic products, particularly F- ions, significantly decreased UO2^2+ partitioning.
• Water washing effectively removed radiolytic products of the [NTf2]- anion, largely restoring UO2^2+ partitioning.

Conclusions:

• Radiation exposure leads to the degradation of [HOOCCH2MIM][NTf2], impacting its performance in UO2^2+ extraction.
• Fluoride ion competition is a primary factor limiting UO2^2+ partitioning in irradiated ionic liquids.
• The developed ionic liquid shows potential for uranium extraction, with recovery possible after managing radiolytic byproducts.