Filtration-Based Iodine Capture Using Nanoporous MOF-Embedded PVDF Beads: A Sustainable Strategy for Multiphase Radioactive Iodine Sequestration

The radioactive iodine isotopes (129I and 131I), generated during nuclear fission, are volatile and bioaccumulative, persisting in gaseous and aqueous phases, thereby posing significant long-term risks. Two metal–organic frameworks (MOFs), SVNIT-1 and SVNIT-2, featuring building blocks with -NH functional linkages, have been incorporated into polyvinylidene fluoride (PVDF) matrices via nonsolvent-induced phase separation (NIPS). This process resulted in the formation of SVNIT-1/PVDF and SVNIT-2/PVDF beads, which demonstrated exceptional efficiency in removing iodine from multiple phases. The developed beads were characterized by using FTIR, PXRD, TGA, SEM, BET, and XPS techniques, confirming their structural and functional integrity. The iodine adsorption capacities were assessed in vapor, organic, deionized water, and seawater environments, exhibiting values of 4.1 g g–1 and 3.7 g g–1 in the vapor phase; 1.98 g g–1 and 1.82 g g–1 in organic media; and 1.94 g g–1 and 1.77 g g–1 in deionized water, with comparable performance observed in seawater. Additionally, the beads were tested for iodine removal via syringe filtration and dynamic filtration, showcasing their practical applicability. Extensive desorption, recyclability, and stability studies confirmed the robustness and reusability of these materials. Mechanistic investigations highlighted the critical role of -NH linkages in facilitating iodine adsorption through strong host–guest interactions.