High-temperature-resistant fiber-based aerogel composites for dynamic capture of low-concentration radioactive iodine...

Efficient and selective capture of radioactive iodine vapor during nuclear fuel reprocessing is crucial for nuclear safety and environmental protection. In this work, first-principles calculations were employed to guide material design. Adsorption models of cellulose-iodine and polyethyleneimine (PEI)-iodine were investigated using density functional theory (DFT). The results show that nitrogen-containing sites exhibit significantly stronger affinity toward iodine than oxygen-containing sites, with maximum adsorption energies of -0.781 and -0.344 eV, respectively. Guided by these findings, a nitrogen-rich functionalized cellulose aerogel (CAP) was synthesized via GPTMS-assisted grafting of PEI, followed by the introduction of nano-hydroxyapatite (HAP) to enhance thermal stability, yielding CAP-HAP. The composite shows improved thermal stability by 23.67% at 500 °C. CAP-HAP achieved a high static iodine adsorption capacity of 4438 mg/g at 75 °C for 24 h and a dynamic adsorption capacity of 1922 mg/g under low-concentration iodine vapor conditions at 75 °C and 5.5 ppm. The adsorption mechanism is attributed to charge-transfer interactions between amine groups and iodine, leading to the formation of polyiodide species (e.g., I₃^-). This work provides a simple, sustainable, and effective strategy for radioactive iodine capture and immobilization.