Influence of Interfering Ions and Adsorption Temperature on Radioactive Iodine Removal Efficiency and Stability of Ni-MOF-74 and Zr-UiO-66

Abstract

Metal−organic frameworks (MOFs) often exhibit an exceptional adsorption-based separation performance for a variety of gases, ions, and liquids. While most radioactive iodine removal studies focus on the capture of radioactive iodine from off-gas streams, few studies have systematically investigated the effect of structure−property relationships of MOFs on iodine removal performance in the presence of interfering ions in liquid solutions. Herein, we investigated the iodide ion (I − ) adsorption performance of two model MOFs (e.g., Ni-MOF-74 and Zr-UiO-66) in liquid phase as a function of iodine concentration (e.g., 0.125 to 0.25 and 0.50 mmol/ L) and adsorption temperature (e.g., 25 to 40 and 60 °C), and in the presence of interfering ions such as Cl − and CO 3 2− through batch-mode experiments. Under identical experimental conditions, Ni-MOF-74 outperformed Zr-UiO-66 in immobilizing iodine from the solution by achieving a maximum iodine removal efficiency of 97% at 60 °C. The results showed that the presence of other interfering ions marginally affects the iodine removal efficiency (e.g., capacity and rate of iodine capture) over both MOF adsorbents. The adsorption kinetics was found to be controlled by multiple transport processes encompassing external surface adsorption, intraparticle diffusion, and final equilibrium. Moreover, the leach test results revealed 8 and 12% iodine release from Ni-MOF-74 and Zr-UiO-66, respectively, at 25 °C after 48 h aging. This study establishes guiding principles for sustainable removal of iodine in the presence of Cl − and CO 3 2− species in cyclohexane.

Consolidation of Iodine-Laden Adsorbents into Cementitious Waste Forms Suitable for Geological Disposal

“…Since the loading of adsorbents (as additives or fillers) can alter the hydration process, type III cement was specifically chosen for this formulation. Al 2 O 3 -DMAPS and UiO-66-NH 2 adsorbents were considered in this work on the account of their high iodine removal efficiencies, as demonstrated previously. − The octahedral UiO-66-NH 2 has one of the highest iodine adsorption capacities of up to 18.45 wt % coordinated by the high surface energy and the bond formation between the Zr and iodine . In our previous work, we demonstrated the efficacy of Zr-UiO-66 in immobilizing iodine from aqueous solution under various temperature and feed concentrations.…”

“…10−12 The octahedral UiO-66-NH 2 has one of the highest iodine adsorption capacities of up to 18.45 wt % coordinated by the high surface energy and the bond formation between the Zr and iodine. 13 In our previous work, 11 we demonstrated the efficacy of Zr-UiO-66 in immobilizing iodine from aqueous solution under various temperature and feed concentrations. Moreover, Al 2 O 3 -based adsorbents have been shown to display low leach rates.…”