Investigation of bismuth-based metal-organic frameworks for effective capture and immobilization of radioiodine gas.

In this study, we investigated the use of Bi-mna, a specific type of bismuth metal organic framework (MOF) for the capture and disposal of iodine, a key nuclide of concern in nuclear fuel reprocessing plants and nuclear power plants. To find the suitable form of Bi-mna for the purpose, experiments were performed by synthesizing four different Bi-mna with varying reagent ratios and connecting iodine adsorption and conversion for immobilization. After iodine adsorption and characterization to investigate their adsorption mechanisms, the Bi-mna samples went through conversion for immobilization to fix captured iodine into the adsorbents. The converted materials are characterized to examine their thermal stability. The Bi-2mna, showing the best performance of adsorption and thermal stability after the conversion, was selected to explore its chemical stability. According to the test results, the converted compound showed relatively low leaching rate (3.06 ×10 g/m∙day) compared with other iodine containing waste forms for disposal. Based on the results, we proposed the Bi-2mna as a candidate material as iodine adsorbent as well as waste form precursor. ENVIRONMENTAL IMPLICATION: Radioiodine a key nuclide of concern in nuclear fuel reprocessing plants and nuclear power plants. Once ingested, it is accumulated in thyroid grand, causing negative health effects. Currently, a typical radioiodine adsorbent is silver-based zeolites. Despite a strong affinity to iodine of silver, it has a chemical toxicity that causes a potential issue in disposal. Therefore, it is substantially required to develop new type of adsorbents which are both good for capture and disposal of radioiodine. In this respect, we suggested a bismuth-based metal-organic framework as an alternative adsorbent to manage the life cycle of radioiodine.