Technetium-99 has become an environmental concern at Department of Energy nuclear waste sites, such as Hanford, WA, due to the Manhattan Project. 99Tc is the focus of this research because it is generally present in its most stable form, pertechnetate (TcO4-), which is soluble and mobile. The half-life of 99Tc is approximately 2.13x105 years, making the threat to the water tables even more challenging because the radionuclide is so long-lived. Immobilization is the main solution to this 99Tc threat. Initially, the focus was to study the interactions between hydrogen sulfide (H2S) and pertechnetate and potentially apply it as an immobilization technique. The result, however, proved to be less stable than other options, such as interactions with iron sulfide. Research has shown that the interaction between Fe-bearing minerals and SH- can create a reactive surface of FeS that may be used to immobilize and precipitate TcO4-. The FeS-TcO4- reaction was investigated under different conditions to determine the parameters under which the iron sulfide most effectively immobilizes pertechnetate. Different oxidation states of iron were investigated by evaluating different minerals goethite, hematite, and magnetite. This furthers the understanding of the FeS-TcO4- reaction and contributes to finding the most efficient way to eliminate this threat to the environment.

Environmental technetium chemistry: Sulfide treatment of iron-containing minerals

253rd National Meeting (2017)

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