High-efficiency iodine capture in waste biomass-based activated carbon: Effects of biomass types on iodine adsorption and its mechanism

Abstract The generation of radioactive iodine isotopes during nuclear energy utilization can cause serious harm to the ecological environment and public safety. While porous activated carbon shows promise for iodine capture, balancing its adsorption performance with production costs is a central challenge that hinders its practical adoption in nuclear waste management and emergency response. In this study, porous activated carbons were prepared from agricultural wastes such as rice straw, corn stover, soybean straw, rapeseed straw, and rapeseed cake through hydrothermal carbonization and KOH activation methods. The results showed that the porous activated carbon derived from rapeseed cake (RS) had the highest specific surface area (2025 m 2 /g), with iodine adsorption capacities of 5078 mg/g for iodine vapor, 1128 mg/g for iodine in cyclohexane solution, and 2187 mg/g for iodine in aqueous solution. The adsorption of iodine vapor and iodine in aqueous solution was primarily attributed to the micropores and mesopores of the ACs, while iodine adsorption in cyclohexane solution was predominantly governed by micropores of the ACs. Moreover, the adsorption behavior of ACs followed pseudo-second-order kinetics and Langmuir isotherm models, indicating that the adsorption process was primarily physical adsorption. These results provide a theoretical basis for the further design and development of adsorbents for iodine capture from nuclear waste and nuclear accidents, as well as for the high-value utilization of agricultural waste.