Capture of iodine gas by Bi-based composites derived from rice husk: Influence of the type of support on the iodine adsorption and retention

The development of Bi-based composites with low cost, high adsorption capacity and retention is highly desired for iodine gas capture. Herein, three novel Bi-based composites (Bi0-SiO2, Bi0-C/SiO2 and Bi0-C) were prepared by simple sintering process using rice husk as C and SiO2 sources and applied for iodine gas capture. The results demonstrated that the type of support strongly affected the iodine adsorption and retention. The Bi0-SiO2, Bi0-C/SiO2 and Bi0-C composites exhibited the iodine adsorption capacity of 812, 911 and 1334 mg/g, and the iodine retention ratio of 90.9, 86.9 and 65.4%. The Bi0-SiO2 showed the highest iodine retention because the SiO2 supports have no affinity for iodine and the adsorption mainly came from the chemical adsorption of Bi0 (2Bi + 3I2 = 2BiI3). While the Bi0-C exhibited the highest adsorption capacity due to the synergistic adsorption effect between C supports and Bi0 sites. Except for the chemical reaction, charge transfer between C and I (C-I) also contributed to the iodine adsorption. The results demonstrated that the new Bi-based composites would be promising iodine gas adsorbent and the new strategy could be extended to the development of other adsorbents.