Functionalized collagen fiber with specific recognition sites for highly efficient iodine capture: theoretical calculations and experimental verification

The efficient and specific capture of radioiodine vapor during the post-fuel processing is essential for the sustainable development of nuclear energy. In this study, Density Functional Theory (DFT) calculations were employed to investigate the adsorption capabilities and mechanisms of iodine vapor by composite materials (Pyrimidine@ACF, Pyrazole@ACF, and Thiazole@ACF) obtained through functionalization of activated carbon fiber (ACF) with pyrimidine, pyrazole and thiazole moieties. The DFT results indicate that the nitrogen heterocycle 3-aminopyrazole exhibits the highest iodine adsorption energy (-11.06 kJ/mol). Among the active groups on the ACF, the carbonyl moiety (C = O) demonstrates the utmost iodine adsorption energy (-45.04 kJ/mol). The designed composite functional materials show a substantial enhancement in iodine adsorption capability, with Pyrazole@ACF displaying the maximum iodine adsorption energy of -63.53 kJ/mol. The experiments demonstrate that the iodine vapor capture capacity of composite functional materials is significantly enhanced compared to ACF (1.010 g/g). Notably, Pyrazole@ACF demonstrates an iodine vapor capture capacity of 2.586 g/g. The iodine capture mechanism of the composite materials is primarily attributed to the active functional groups on ACF, as well as the charge transfer between the nitrogen heterocycles introduced through functionalization and iodine molecules. This ultimately leads to the capture of iodine molecules by the formation of I3- polyiodides. Consequently, the nitrogen heterocycles functionalized activated collagen fiber composite material can be considered as an ideal candidate for efficient and specific capture of iodine vapor in radioactive gaseous effluents.