High Retention Immobilization of Iodine in B–Bi–Zn Oxide Glass Using Bi2O3 as a Stabilizer under a N2 Atmosphere

The immobilization of iodine waste suffers from serious iodine loss during heat treatment. Herein, we reported on the high iodine retention immobilization of simulated radioiodine-contaminated Bi⁰-SiO₂ sorbent in B-Bi-Zn oxide glass using Bi₂O₃ as a stabilizer under a N₂ atmosphere. The effects of the Bi₂O₃ content and sintering atmosphere on the iodine immobilization behaviors (iodine retention ratio, phase composition, microstructure, and chemical stability) were investigated. It was found that the decomposition of BiI₃ was prevented by adding Bi₂O₃ and sintering in a N₂ atmosphere. The iodine retention ratio in the obtained glass waste form was significantly enhanced with increasing Bi₂O₃ content and sintering in the N₂ atmosphere due to the synergistic effect. The achieved record-high iodine retention (92.22 ± 2.6%) was much higher than that of conventional heat treatment route (18.01 ± 3.5%). The results demonstrated that iodine was effectively immobilized through the formation of stable Bi_xO_yI (Bi₅O₇I and BiOI). Furthermore, the obtained iodine waste form exhibited excellent compactness and chemical stability. Owing to its high iodine retention ratio, this route can be employed to effectively immobilize radioactive iodine.