Evaluation of Silver Zeolites Sorbents Toward Their Ability to Promote Stable CH 3 I Storage as AgI Precipitates
Résumé
In this study, up to 13 different silver zeolites sorbents were prepared by repeated ion exchange from their parent structures (FAU X and Y, MOR, *BEA, MFI, FER), characterized, and evaluated for their ability to capture methyl iodide in the context of a nuclear severe accident. A novel methodology was implemented to establish structure–activity relationships between sorbent properties and iodine trapping stability. After saturation of the zeolite bed with CH3I during a dynamic breakthrough experiment at 100 °C, a two-step quantitative desorption method was elaborated with the aim to quantify separately the CH3I fractions trapped by physisorption, chemisorption, or reacted as AgI precipitates. Besides, an analysis of the mechanisms involved in CH3I sorption and decomposition processes was also carried out. Overall, Ag/Y zeolites displayed the highest fractions trapped as stable AgI precipitates, thanks to the presence of high amounts of dispersed silver species at accessible locations in the large supercages, and their low sodium content.