Chalcogen-based aerogels as sorbents for radionuclide remediation

The efficient capture of radionuclides with long half-lives such as technetium-99 (⁹⁹Tc), uranium-238 (²³⁸U), and iodine-129 (¹²⁹I) is pivotal to prevent their transport into groundwater and/or release into the atmosphere. While different sorbents have been considered for capturing each of them, in the current work, nanostructured chalcogen-based aerogels called chalcogels are shown to be very effective at capturing ionic forms of ⁹⁹Tc and ²³⁸U, as well as nonradioactive gaseous iodine (i.e., a surrogate for ¹²⁹I₂), irrespective of the sorbent polarity. The chalcogel chemistries studied were Co_0.7Bi _0.3MoS₄, Co_0.7Cr_0.3MoS₄, Co_0.5Ni_0.5MoS₄, PtGe₂S₅, and Sn₂S₃. The PtGe₂S₅ sorbent performed the best overall with capture efficiencies of 98.0% and 99.4% for ⁹⁹Tc and ²³⁸U, respectively, and >99.0% for I ₂(g) over the duration of the experiment. The capture efficiencies for ⁹⁹Tc and ²³⁸U varied between the different sorbents, ranging from 57.3-98.0% and 68.1-99.4%, respectively. All chalcogels showed >99.0% capture efficiency for iodine over the test duration. This versatile nature of chalcogels can provide an attractive option for the environmental remediation of the radionuclides associated with legacy wastes from nuclear weapons production as well as wastes generated during nuclear power production or nuclear fuel reprocessing.