Fabrication of hierarchical porous chitosan/polyphosphazene monolithic aerogels for efficient iodine adsorption

Adsorption is effective for removing radioactive iodine in nuclear wastewater treatment, while composite adsorbents can optimize the adsorption performance of adsorbents. In this work, Chitosan and polyphosphazene were used to prepare an aerogel monolith (CS/PCD) with facile recyclability, high hydrophilicity, ultra-lightweight properties, and hierarchical porous structure via hydrothermal synthesis and freeze-drying. Under static conditions, the effects of adsorbent dosage, pH, coexisting ions, and contact time on iodine adsorption were studied. The results demonstrate that CS/PCD reaches a saturated iodine adsorption capacity of 1.20 g·g −1 in aqueous solution, exhibiting good regeneration performance and anti-ion interference capability in accordance with the Freundlich isotherm and pseudo-second-order kinetic models. Under dynamic adsorption conditions, the breakthrough behavior further confirms the material’ effective iodine capture performance. Notably, CS/PCD exhibited a broad applicable pH range (3–8) and good acid-base stability. Furthermore, CS/PCD also demonstrates exceptional performance in gaseous iodine adsorption, achieving a saturation capacity of 3.49 g·g −1 at 348 K. FT-IR and XPS analysis revealed the driving force of adsorption arises from charge transfer through N and O atoms, π-π stacking, hydrogen bonding (N-H···I and O-H···I), and hierarchical porous (microporous-mesoporous-macroporous). In conclusion, this work develops a high-efficiency monolithic adsorbent for radioactive iodine capture, offering a promising continuous-flow method for nuclear wastewater treatment.