Oxidative dissolution of TcO2 by Mn(III) minerals under anaerobic conditions: Implications on technetium-99 remediation

Transformations and Speciation of Iodine in the Environment as a Result of Oxidation by Manganese Minerals

“…The synthesis and characterization of γ-MnOOH and acid δ-MnO 2 were completed following previously reported procedures. , The α-Mn 2 O 3 (99%, Strem Chemicals) and β-MnO 2 (98%, Alfa Aesar) were commercially purchased.…”

“…It has been previously observed that Mn 2+ is unable to sorb onto α-Mn 2 O 3 , resulting in all of the released Mn 2+ to be found in the aqueous phase. 32 Therefore, there are processes other than the redox reaction causing Mn 2+ to be released in the aqueous phase, as seen by the nonstoichiometric release of Mn 2+ even after the oxidation reaction plateaus (Figure 3d). In the control samples, there was minimal amounts of Mn 2+ release, indicating that the extensive Mn 2+ release is reaction dependent.…”

“…The analysis parameters and the γ-MnOOH characteristic peaks have been described elsewhere in detail. 3,32 These XRD spectra were combined with those from the purchased manganese oxide minerals, as seen in Figure S1, with the reference peaks listed for comparison in Table Supporting Information. 11,34−36 ■ RESULTS AND DISCUSSION Oxidation of I − by Manganese Minerals.…”

“…42 Nevertheless, both γ-MnOOH and α-Mn 2 O 3 are generally more reactive along the edge sites, which are known to be the active sites responsible for sorption to take place. 43 Only on the surface of α-Mn 2 O 3 are there anion vacancies that allow for the accessible sorption of I − , as seen by the sorption of I − for its oxidation to take place. 17 The oxidation of I − can be wholly attributed to the presence of the redox active manganese oxides, as the oxidation by dissolved oxygen is very slow or unfavorable under the experimental conditions.…”

“…However, the effect of sorption of divalent cations on the oxidative capacity of manganese minerals seems to be mineral and contaminant specific: a study on the solid−solid oxidation of TcO 2 using α-Mn 2 O 3 showed that the sorption of Ca 2+ decreased the extent of the reaction, though the initial reaction rate remained unchanged, and there was release of calcium in the aqueous phase as a results of the oxidative dissolution process. 43…”