Master of Science (MS)
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Radioactive waste, Technetium-99, zero-valent iron, reductive removal
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Treatment to immobilize radioactive waste is of concern for long-term storage, avoiding future environmental exposure. Most production of Technetium-99 (99Tc) occurred as a byproduct of development of legacy nuclear weapons research. Zero-valent iron (ZVI) is a promising reductant of Tc(VII) to a less mobile 99Tc(IV). However, more redox-sensitive contaminants can compete in the reductive process. Therefore, it is important to examine the effects of competitive contaminants and quantify the effects on the reductive removal rates of 99Tc. Chromate, Cr(VI), is a redox-sensitive contaminant that is expected to be present in legacy waste present in the Hanford site’s low activity waste streams. The competitive kinetics of Cr(VI) and Tc(VII) reduction by ZVI was studied in basic conditions over a range of Cr(VI) concentrations. The removal rate of 99Tc(VII) slowed down with increasing Cr(VI) concentrations. A second-order kinetic model showed the best fit for the reduction rates of Tc(VII) and Cr(VI).
Williams Ramirez, Jonathan, "Competitive Reductive Removal of Chromate and Pertechnetate via Zero-valent Iron" (2021). FIU Electronic Theses and Dissertations. 4622.
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