Development of bismuth-mordenite adsorbents for iodine capture from off-gas streams

Abstract

• Development of bismuth-doped mordenite adsorbents with various bismuth loadings. • Higher surface area and porosity for the bismuth-modernite than that for bare mordenite. • 2.5-fold increase in iodine capacity for bismuth-modernite than that for bare mordenite. • 36% of iodine release to water from the iodine-loaded adsorbents. The search for efficient, cheap, and robust sorbent materials which can effectively remove iodine compounds from off-gas streams in used nuclear fuel reprocessing facilities is still challenging. Herein, we report the development of bismuth-doped mordenite zeolite with different loadings for removal of iodine-129 ( 129 I) from nuclear waste off-gas streams. Of the materials investigated, bismuth-mordenite with 5 wt% bismuth content (Bi 5 @Mordenite) exhibited the highest capture capacity with an iodine uptake capacity up to 538 mg/g after exposure to iodine for 6 h at 200 °C, which was ~2.5 times higher than that of the bare mordenite with relatively fast kinetics. Interestingly, the bismuth-doped mordenite sample exhibited higher surface area and porosity than those of the bare zeolite as a result of mordenite dealumination during bismuth incorporation. Moreover, the leach tests were carried out to determine the degree of iodine leaching from the iodine-loaded Bi 5 @Mordenite upon coming into contact with DI water and the results revealed a maximum iodine amount of 36% that was released from the adsorbent after 24 h exposure, highlighting the necessity of transforming the iodine-loaded adsorbent into a suitable waste form for permanent geological disposal. Overall, the high uptake capacity and fast uptake rate of iodine reveal the potential utility of bismuth-based zeolites as iodine capture materials when consolidated into a waste form for long-term decay storage.