Recent advances in iodine adsorption from water

The removal of radioactive contaminants from the environment can be a matter of urgent concern. This is true for the radioactive iodine isotopes 131I and 129I. These volatile radioactive pollutants can enter the environment as the result of untoward release during nuclear waste disposal or as the result of nuclear accidents. They enter waterways through direct leakage or through release into the atmosphere followed by deposit on the earth and leaching into water. The hazardous nature of these two isotopes has prompted efforts to develop methods that permit the effective capture and storage of radioactive iodine from aqueous source phases. This review provides a summary of recent progress in the area of porous organic materials useful for iodine adsorption from water. Four types of porous materials, namely metal–organic frameworks (MOFs), covalent organic frameworks (COFs), porous organic polymers (POPs), supramolecular macrocycles and macrocycle-containing polymer networks (MPNs), have dominated these efforts. They are thus systematically analyzed and their relative merits and demerits summarized. Various mechanisms of iodine adsorption and the factors influencing iodine capture in water are also discussed. Finally, outstanding challenges and possible future developments within this research field are outlined from the authors' perspective.