Grafted mesoporous silicas for radionuclide uptake: Radiolytic stability under electron irradiation
Résumé
Materials developed for radionuclide adsorption need to resist harsh conditions, i.e. be robust against ionizing radiation. In this work, we evaluated the degradation of mesoporous silicas (SBA-15) grafted with hydroxypiridinone, acetamide phosphonate and propionamide phosphonate ligands under electron irradiation. The ligands contained amide and phosphinic acid functional groups, which made them able to bind to actinides. Degradation of the grafted ligand was assessed by identifying and quantifying the gas produced under irradiation using gas chromatography, as well as characterizing the grafted ligands before and after irradiation by means of FT-IR, XPS and TGA techniques. Irradiation led to the degradation of amide functional groups and to the production of amine and carboxylic acid groups. Corresponding reaction mechanisms are proposed. The sorption behavior of the grafted SBA-15 materials for thorium was also studied. SBA-15 materials grafted with acetamide phosphonate and propionamide phosphonate ligands were shown to be able to adsorb thorium. The propionamide phosphate ligand was the most efficient, with an equilibrium sorption capacity of 95 mg g$^{−1}$. This capacity remains stable up to a 1 MGy irradiation dose and undergoes a 20% decrease after 4 MGy of irradiation. Therefore, this material is potentially interesting for the treatment of liquid outflows contaminated by actinides produced in nuclear facilities.
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