Green ionic liquid engineering for efficient and stable radioactive iodine capture: a review of the fundamentals and future perspectives

Abstract

The safe and efficient capture of radioactive iodine (e.g., ¹²⁹I and ¹³¹I) from nuclear waste streams is a critical environmental and public health imperative for sustainable nuclear energy. While diverse adsorbents have been explored, ionic liquids (ILs) emerge as exceptionally promising green and designable platforms due to their negligible volatility, tunable structures, and versatile capture mechanisms. This review comprehensively summarizes the significant advancements in IL-based materials for radioactive iodine capture. We critically analyze the fundamental interactions driving iodine uptake, including halogen bonding, coulombic forces, and π-I interactions, and establish the crucial structure–activity relationships governing the adsorption capacity and long-term stability. Beyond pristine ILs, the review highlights innovative strategies such as IL functionalization (e.g., with curcumin and tetrazoles), polymerization (e.g., PILs), and the development of supported or composite materials (e.g., IL@MOFs, IL@MF composites, and PIL@CC3 membranes) that synergistically enhance performance. Particular emphasis is placed on environmentally benign approaches including the use of bio-derived IL precursors (e.g., choline, amino acids, and alginate) and strategies to mitigate the limitations of certain conventional ILs. We discuss the key challenges in regeneration, recyclability, and scalability and the true green credentials of IL-based systems (considering synthesis, toxicity, and lifecycle). Finally, the review outlines future research directions focused on designing high-performance, cost-effective, and genuinely sustainable IL-based sorbents for practical radioactive iodine management, aligning with the principles of green chemistry.