Chalcogen-based aerogels as a multifunctional platform for remediation of radioactive iodine

Abstract

Aerogels employing chalcogen-based (i.e., S, Se, and/or Te) structural units and interlinking metals are termed chalcogels and have many emerging applications. Here, chalcogels are discussed in the context of nuclear fuel reprocessing and radioactive waste remediation. Motivated by previous work on removal of heavy metals in aqueous solution, we explored the application of germanium sulfide chalcogels as a sorbent for gas-phase I₂ based on Pearson's Hard/Soft Acid–Base (HSAB) principle. This work was driven by a significant need for high-efficiency sorbents for ¹²⁹I, a long-lived isotope evolved during irradiated UO₂ nuclear fuel reprocessing. These chalcogel compositions are shown to possess an affinity for iodine gas, I₂(g), at various concentrations in air. This affinity is attributed to a strong chemical attraction between the chalcogen and I₂(g), according to the HSAB principle. The high sorption efficiency is facilitated by the high porosity as well as the exceptionally large surface area of the chalcogels. This paper briefly discusses the current and alternative waste forms for ¹²⁹I, elaborates on preliminary work to evaluate a Pt-Ge-S chalcogel as a I₂(g) sorbent, and discusses the unknown chalcogel properties related to these materials in waste form.