Adsorption performance study of bismuth-doped ZIF-8 composites on radioactive iodine in the vapor and liquid phases

Abstract

Radioactive iodine generated from nuclear waste and nuclear accidents can cause serious hazards to the environment and human body. In this study, bismuth-doped ZIF-8 composites (Bi2O3@ZIF-8) were synthesized by in situ synthesis at room temperature to study their adsorption of iodine in gaseous state and in solution. The Bi2O3@ZIF-8 composites were characterized and analyzed by means of tests. Bi2O3@ZIF-8 exhibited high specific surface area and contained abundant microporous structures. However, when the bismuth doping amount reached 10%, 10%-Bi2O3@ZIF-8 appeared mesoporous. The specific surface area of 1%-Bi2O3@ZIF-8, 5%-Bi2O3@ZIF-8 and 10%-Bi2O3@ZIF-8 could reach 1110.6 m2/g, 973.21 m2/g and 927.82 m2/g, respectively. The adsorption of gaseous iodine by 5%-Bi2O3@ZIF-8 reached equilibrium after 3.5 h with the maximum adsorption capacity of 298 wt%. And the maximum adsorption capacity of iodine in solution was 751.4 mg/g. The effects of the initial concentration of the solution, reaction temperature and contact time on the adsorption process were investigated. The adsorption of Bi2O3@ZIF-8 on iodine was consistent with the pseudo-second-order kinetics and the Langmuir model. The results of thermodynamic studies indicated that the adsorption of iodine by Bi2O3@ZIF-8 was spontaneous and exothermic. This study provides a reference for the synthesis of metal organic framework-based materials and provides theoretical guidance for the removal of practical radioactive iodine.