Imidazolyl ionic liquid-based hypercrosslinked polymers as adsorbents for reversible capture of iodine

Nuclear energy is regarded as one of the most promising alternatives to fossil fuels due to its low greenhouse gas emissions and high energy density. However, the increased utilization of nuclear energy will inevitably lead to the production of radioactive iodine, which is highly volatile, easily diffusible, strongly bioaccumulative, and has a long half-life. Consequently, the design and synthesis of adsorbents that can effectively remove radioactive iodine from nuclear waste is a critical issue that urgently needs to be addressed. Ionic liquids exhibit great application potential in adsorption and separation fields owing to their unique physical and chemical properties and structural design flexibility. In this study, three types of imidazolyl ionic liquid-based hypercrosslinked polymers (IHCPs) were synthesized via the Friedel-Crafts reaction. IHCPs possess excellent thermal stability and a rich porous structure, demonstrating outstanding iodine capture performance and recyclability. Among them, the adsorption capacity of IHCP-1 for static iodine vapor and dynamic iodine vapor reached 4.10 g/g and 1.86 g/g, respectively. In solution systems, IHCP-1 exhibited adsorption capacity of 888.44 mg/g and 222.02 mg/g for iodine aqueous solution and iodine cyclohexane solution, respectively. The adsorption process of iodine by IHCPs conforms to the pseudo-second-order model and the Freundlich isotherm model. Combined with FT-IR and XPS, it was confirmed that the adsorption process is primarily governed by heterogeneous surface multilayer chemical adsorption. This study marks the first design and synthesis of imidazolyl ionic liquid-based hypercrosslinked polymers, which serve as ideal adsorbents for iodine vapor and iodine solutions.