Technetium-99 is a radionuclide of environmental concern due to its long half-life (2.13x105 years), radiotoxicity and high mobility under oxidizing conditions. Poor past radioactuve waste management practices led to the release of Tc-99 into the environment, where under oxidizing conditions, it exists as highly soluble pertechnetate (TcO4-), whereas under reducing conditions Tc(IV) forms predominate, which are sparingly soluble. Manganese minerals, such as birnessite (Mn3+,4+ oxide) and manganite (MnOOH) can be effective oxidizing agents, due to the fact that the high redox potential of Mn(IV)/Mn(II) makes oxidation of reduced metals in the presence of Mn-minerals almost always thermodynamically favorable. We showed that birnessite constitutes a liability for the stability of TcO2 phases, since it is capable of oxidizing TcO2 to soluble pertechnetate even in the absence of oxygen at different pH values and at different TcO2:Mn-oxide ratios. Our currents experiments explore the potential passivation" of manganese minerals due to the sorption of divalent cations, such as Ca2+, Mg2+ on the mineral surface, as well as potential hindrance of electron transfer due to secondary mineral precipitation, such as MnCO3 in carbonate rich systems.

Tc(IV) oxidative dissolution by manganese oxides under suboxic conditions

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.