Capture of iodine gas by Bi⁰ modified silica with different morphologies: Influence of pore characteristic on the stable and unstable forms of adsorption

Exploring efficient iodine gas adsorbent is a meaningful and challenging topic in the field of radioactive waste treatment. Herein, Bi-0 modified SiO2 with different morphologies (platelet-like, rod-like, and sphere-like) were fabricated by an improved impregnation method using SnCl2 as reductant. The iodine gas adsorption behaviors of the obtained materials were systematically investigated. The effects of pore characteristic, temperature and time on the adsorption capacity including total, chemical (stable form) and physical (unstable form) were studied. Pore characteristic and temperature affected not only the total adsorption, but also the stable and unstable forms of adsorption. The results demonstrated that the platelet-like Bi-0 modified SiO2 (Bi-0@SiO2-P) with ordered, short and straight pore characteristics had the highest total adsorption capacity (up to 960 mg/g), while sphere-like (Bi-0@SiO2-S) with disordered pore showed the highest ratio of stable form of adsorption (94.8 %). Furthermore, with increasing temperature, the total and unstable form adsorption decreased slightly, but stable form increased. The adsorption processes were better fitted by the pseudo-second-order kinetic equation. The results demonstrated that I-2 adsorption for Bi-0 modified SiO2 materials was mainly chemical (Bi + I-2 = BiI3).