Glass composite waste forms for iodine confined in bismuth-embedded SBA-15

The aim of this study was to stabilize bismuth-embedded SBA-15 that captured iodine gas by fabrication of monolithic waste forms. The iodine containing waste was mixed with Bi₂O₃ (a stabilizing additive) and low-temperature sintering glass followed by pelletizing and the sintering process to produce glass composite materials. Iodine volatility during the sintering process was significantly affected by the ratio of Bi₂O₃ and the glass composition. It was confirmed that BiI₃, the main iodine phase within bismuth-embedded SBA-15, was effectively transformed to the mixed phases of Bi₅O₇I and BiOI. The initial leaching rates of iodine from the glass composite waste forms ranged 10⁻³–10⁻² g/m² day, showing the stability of the iodine phases encapsulated by the glassy networks. It was also observed that common groundwater anions (e.g., chloride, carbonate, sulfite, and fluoride) elevated the iodine leaching rate by anion exchange reactions. The present results suggest that the glass composite waste form of bismuth-embedded SBA-15 could be a candidate material for stable storage of ¹²⁹I. - Highlights: • Glass composite waste forms were developed to stabilize iodine confined in Bi-embedded SBA-15. • BiI₃ within Bi-embedded SBA-15 was transformed to BiOI and Bi₅O₇I during sintering process. • Iodine volatility was significantly affected by glass composition and Bi₂O₃ additive. • Iodine leaching rates were 10⁻³–10⁻² g/m² day due to the stable iodine phases encapsulated by glassy networks. • Glass composite waste form of Bi-embedded SBA-15 is expected to be a candidate material for stable storage of ¹²⁹I.