An Electrochemical Oxidation and Intercalation Strategy for Iodide Removal Using LDHs

Radioactive iodide harms the ecosystem and human health, necessitating its immobilization to mitigate aquatic iodine pollution. Layered double hydroxides (LDHs), a family of 2D clays with intercalated anions and controllable interlayer structures, are technologically and economically viable adsorbents to eliminate various anion pollutants. However, LDHs exhibit an extremely low affinity toward iodide species. Here, an electrochemical oxidation and intercalation strategy is developed to successfully remove and immobilize iodide using LDHs. The iodide can be transformed into I₂/I₃ ^- and subsequent IO₃ ^- ions on NiFe-LDH/CC electrode at 0.6 and 1.0 V (vs Ag/AgCl), with an iodine adsorption capacity of 962 and 355 mg g^-1, respectively. I₂/I₃ ^- are adsorbed on the surface of NiFe-LDH with a weak interaction, while IO₃ ^- inserts into the interlayer of LDH with a high affinity due to the strong hydrogen bonding and coordination between IO₃ ^- and Ni atoms. This LDH-based electrochemical removal strategy also has high adaptability to a low iodide concentration, wide pH range, and outstanding ion selectivity. This study can lay the foundation for efficient iodide elimination and immobilization from radioactive liquids.