Biomass chitosan-derivative-based hypercrosslinked polymers as high-efficiency iodine adsorbents

With the intensification of the global energy crisis, nuclear energy, as a clean and low-carbon energy source, has been widely applied. However, spent fuel from nuclear power plants releases nuclear radioactive waste containing iodine, which exhibits rapid diffusion and high volatility, thereby posing severe risks to human health and the ecosystem. In this study, chitosan-based hypercrosslinked polymers (MCHCPs) were synthesized by modifying chitosan as a raw material via a Schiff base reaction, followed by Friedel-Crafts reactions using different cross-linking agents; these materials exhibited excellent thermal stability, a high specific surface area, and a rich porous structure. Among them, the adsorption capacity of MCHCP-1 for static iodine vapor and dynamic iodine vapor reached 8.49 and 2.38 g/g, respectively. Furthermore, MCHCP-1 achieved adsorption equilibrium for iodine in aqueous solution within 2.5 min, with a removal rate of 98.7% and a maximum adsorption capacity of 1941 mg/g. Moreover, the iodine adsorption process of MCHCPs conformed to pseudo-second-order kinetics and the Langmuir model. The results indicate that the adsorption process of iodine by MCHCPs was primarily governed by monolayer chemisorption through interactions between the polymer and iodine molecules. After five adsorption-desorption cycles, the adsorbents retained over 85% of their original iodine vapor uptake capacity, reflecting excellent recyclability and significant practical application value.