The water-based synthesis of chemically stable Zr-based MOFs using pyridine-containing ligands and their exceptionally high adsorption capacity for iodine

Abstract

The primary pollutant, radioactive iodine (I₂), has become a worldwide concern due to its serious ill effects of radiotoxicity on human health. Therefore, it is of great significance to develop novel adsorbents for effectively eliminating I₂ from nuclear waste. Herein, we reported a Zr-based MOF adsorbent constructed by utilizing pyridine-containing pyridine-dicarboxylic acid (PYDC) as organic ligands (UiO-66-PYDC) as well as active sites for the efficient removal of I₂. UiO-66-PYDC MOFs were synthesized by a hydrothermal strategy and featured good chemical and thermal stabilities, endowing them with the ability to work in harsh environments. The abundant and inherent pyridine moieties in the developed adsorbent worked as active adsorption sites to capture I₂. The correlation between the most significant parameters such as the contact time, adsorbate concentration, and reusability was optimized, and the interaction mechanism between I₂ and UiO-66-PYDC was investigated in detail. As for the current adsorbent, a pseudo-second order rate equation was used to explain the removal kinetics, and the Langmuir model exhibited a better fit to the adsorption isotherm than the Freundlich model. Thanks to the strong affinity of PYDC ligands to I₂ and high porosity, the adsorption capacities of UiO-66-PYDC for I₂ could reach as high as 1250 mg g⁻¹, which was much higher than those of many other reported MOFs. Additionally, the UiO-66-PYDC MOFs exhibited excellent renewable adsorption properties, prefiguring their great promise as green adsorbents for I₂ removal in nuclear waste management.