Highly stable iodine capture by pillared montmorillonite functionalized Bi₂O₃@g-C₃N₄ nanosheets

Nuclear power is the potential to satisfy the global electricity demand. Iodine (I₂) is an essential input for the fission fuel but also key output as radioactive waste. Thus, efficient capture and long-term storage of iodine is a high priority. Herein, a novel composite of Bi₂O₃ doped graphitic carbon nitride nanosheets and bismuth-pillared interlayered clay, abbreviated as Bi₂O₃@g–CNN–PILC, for vapor iodine capture is reported. The Bi₂O₃ doped graphitic carbon nitride nanosheets (Bi₂O₃@g-CNN) is served to capture the iodine and the bismuth-pillared interlayered clay (Bi-PILC) to provide high stability. The capture capacity of Bi₂O₃@g–CNN–PILC for vapor iodine is 830 ± 44 mg/g at 100 °C within an equilibrium time of almost eight hours despite low specific surface area (S_BET = 11.4566 m²/g). Chemical and physical iodine capture mechanisms were involved. Accordingly, direct reaction of I₂ with Bi₂O₃/Bi to produce BiI₃ and BiOI and charge transfer from the nitrogen lone pair sites were identified as chemisorption processes. The other proposed sorption mechanism (physisorption) was the pore filling (I₂@pore) process. Thermogravimetric analysis showed that the Bi₂O₃@g-CNN-PILC material has lost only 10.7% and 18.7% of its weight before and after iodine capture, respectively, when heated up to 800 °C, showing how stable the material is. According to these preliminary results, the authors highly recommend this material for further investigation as it could be potential iodine storage in the nuclear industry.