The legacy of nuclear events, represented by nuclear accidents, weapon experiments, and wastes generated from nuclear energy production, contributes to the contamination of water with highly toxic, long-lived radionuclides. Technetium-99 (99Tc) is a radioactive element found in relatively large quantities in nuclear waste and contributes significantly to long-term radiation risk to humans. Its prevalent oxidation state, +7, as pertechnetate (TcO4-) in aqueous media, is not adsorbed by most soils and subsurface minerals, leading to its high mobility in the surrounding environment. Therefore, designing and evaluating novel materials that are capable of reducing and extracting 99Tc from environmental and nuclear waste sources are crucially required. In the present work, titanium-based inorganic ion-exchangers were synthesized and evaluated for the reduction and uptake of TcO4-. These synthesized materials have two structural forms, poorly-crystalline silicotitanate (PCST) and sodium nonatitanate (SNT). One approach is based on photocatalytic reduction using UV-radiation. Since all technetium isotopes are radioactive, rhenium (Re) was used as a non-radioactive surrogate of 99Tc in these studies to minimize radiation exposure in optimizing conditions for 99Tc uptake over PCST/SNT. The optimized parameters include pH, equilibration time, initial metal concentration and stability of the evaluated materials. Our results revealed that using UV-light to reduce perrhenate (ReO4-) at a pH of 5 facilitated 100% Re adsorption by SNT ion-exchangers from a solution mixture after an equilibration time of 5 days, using either 25% or 50% isopropanol. The adsorption of Re under these conditions using SNT was best described by the Freundlich model. For the dark experiments, at a pH of 12, our results revealed that the highest uptake was reached after an equilibration time of 2 days, using 50% isopropanol.

Inorganic titanium-based materials as fishing bait for technetium-99 from nuclear wastes tanks

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.