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Physiochemical mechanisms for the transport and retention of technetium

Understanding the transport and retention of radionuclides in the environment is important for protecting freshwater supplies and minimizing impact to biologic systems. Technetium-99 (Tc⁹⁹) is a radionuclide of interest due to its long half-life (2.13 x 10⁵ years) and toxicity. In the form of pertechnetate (TcO₄⁻), Tc is expected to move nearly unretarded in the subsurface. Under reducing conditions Tc can precipitate in low solubility Tc oxide (TcO₂·nH₂O) and/or Tc sulfide (Tc₂S[subscript x]) phases.
The studies presented in this dissertation investigate the physiochemical mechanisms for the transport and retention of Tc. Transport studies determined that TcO₄⁻ would move at pore water velocity in unsaturated sediments. Geochemical studies of contaminated sediments determined that nearly ~ 25 % of the total Tc was retained in phases associated with iron oxide and aluminosilicate minerals, thus reducing the mobility of Tc. Studies of Tc₂S[subscript x] mineral phases, generated using nano Zero Valent Iron (nZVI) and sulfide (HS-) in sediments, determined that Tc could be stabilized in mineral phases as Tc₂S[subscript x] that were slower to reoxidize than TcO₂·nH₂O phases. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from Feb. 14, 2013 - Feb. 14, 2014

Identiferoai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36911
Date14 February 2014
CreatorsJansik, Danielle P.
ContributorsIstok, Jonathan
Source SetsOregon State University
Languageen_US
Detected LanguageEnglish
TypeThesis/Dissertation

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