Adsorption behavior of methyl iodide on a silver ion-exchanged ZSM-5

Abstract

Abstract An organic iodide, especially methyl iodide (CH3I), is one of the most safety concerns against a nuclear power plant severe accident because it is highly toxic and easily inhaled. Due to its high volatility, the dry filtration methods are generally employed to capture the gas phase CH3I. Although it is important to accurately assess the performance of dry filter in a postulated severe accident situation, no sufficiently accurate adsorption kinetic behaviors have been reported yet. In this study, we designed the highly accurate experimental set-up, thermogravimetric analysis-gas chromatography coupled system, which overcame the limitations of previous studies, and performed the CH3I adsorption tests on a silver ion-exchanged ZSM-5 (Ag-ZSM-5) zeolite at a wide temperature range (50–150 °C) under the postulated severe accident condition. The fresh and adsorbed Ag-ZSM-5 samples were characterized by powder XRD, elemental analysis, and SEM-EDS, and the further CH3I adsorption behaviors were discussed in depth. From the overall results, we obtained the accurate adsorption rates and activation energies, and an understanding of chemisorption and physisorption behaviors. Our findings provide the useful fundamentals for a model development of dry filter performance assessment.