ZSM-5 zeolites microstructure study and metal characterization for an optimized xenon adsorption

Molten salt reactors are a class of nuclear fission reactors in which the coolant, which is also the fuel, is a mixture of molten salts. During its operation, fission products, such as krypton and xenon, are generated within the reactor and must be evacuated. Silver-loaded ZSM-5 zeolites have been identified as excellent materials to be used in a fixed bed column process because they have a high Xe capture capacity, but also a really high Xe/Kr selectivity. However, the ZSM-5 microstructure strongly influences silver insertion and the adsorption performance of materials. Moreover, the Ag-Xe interaction remains an open debate in the literature. In this work, the microstructure of ZSM-5 zeolites has been modified by desilication and finely characterized in order to study the evolution of porosity and structural defects. After incorporation of Ag by cation exchange, the adsorption performance of Xe of AgZSM-5 was investigated. To further study the Ag-Xe interaction, silver speciation was subsequently modified by different heat treatments and characterized by UV-Vis spectroscopy and X-ray adsorption. The silver speciation evolution could then be linked to the Xe adsorption performances of materials. Finally, the materials were used in a fixed bed column process, in which the good stability of Ag(at)ZSM-5 zeolites was tested. The atmosphere variation of the conditioning step also enables to optimize the process and highlight the role of the silver speciation in xenon adsorption. (author)