Document Type

Thesis

Degree

Master of Science (MS)

Major/Program

Biomedical Engineering

First Advisor's Name

Anthony McGoron

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Yelena Katsenovich

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Joshua Hutcheson

Third Advisor's Committee Title

Committee Member

Keywords

Radioactive waste, Technetium-99, zero-valent iron, reductive removal

Date of Defense

3-26-2021

Abstract

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).

Identifier

FIDC009709

Available for download on Sunday, March 26, 2023

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