Metal-organic frameworks (MOFs) are capable in capture and storage of iodine ions with high efficiency, and polymer/MOF nanocomposite membrane has the potential to be used for efficient removal of iodine from radioactive wastewater. In this work, we have reported a PVDF/ZIF-8 nanocomposite adsorption membrane prepared by contra-diffusion method. The combination of surface graft of poly(4-vinylpyridien) brushes and optimal addition of sodium formate into ligand contributes to the formation of a well-intergrown and continuous ZIF-8 layer on the metal ions side surface of PVDF- g -P4VP membrane. In the batch adsorption, the PVDF/ZIF-8 nanocomposite membrane exhibits high affinity for iodine following a pseudo-second-order kinetics and fitting the Freundlich isotherm model with a maximum adsorption capacity of 73.33 mg/g. In the dynamic adsorption, the PVDF/ZIF-8 nanocomposite membrane exhibits a high flux of 66.19 L/(m 2 ⋅h⋅MPa) and an iodine removal efficiency of 73% until 180 min. Initial iodine concentration has a little influence on the iodine removal efficiency, but solution pH shows a significant effect. The iodine removal efficiency can be maintained around 92% in a weakly alkaline medium of pH = 8. The PVDF/ZIF-8 nanocomposite membrane possesses an excellent reusability with an iodine removal efficiency of 73.4% after five cycles.
The highly efficient removal of radioactive iodine from nuclear accident-polluted seawater is of great significance for the purpose of environmental protection. Herein, we report an indium-based metal–organic framework, named In-MOF, for highly efficient removing iodine from seawater. In-MOF is constructed by In 3+ ions coordinated with tris (4-(1H-imidazol-1-yl) phenyl) amine and exhibits high chemical stability even under seawater for 30 days. Due to the flexible one-dimensional linear structure and high-density charged imidazolium groups, In-MOF possesses a high adsorption capacity (1138 mg/g) for iodine in water. Furthermore, it exhibits high selectivity in the presence of competitive ions, due to forming the unique I-π interactions between iodine and the In-MOF. Notably, these excellent adsorption features endowed In-MOF successfully remove iodine from seawater with a high removal rate of 93.86%. These results are of fundamental importance to understanding iodine uptake and designing materials with high adsorption capacity.
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