Groundwater composition and coupling with other redox cycles can affect the longevity of U(IV) products from bioremediation. Mn(II) has appreciable concentrations at U-contaminated sites and is redox active. The effect of Mn(II) on UO2 dissolution rates under reducing and oxidizing conditions were investigated using batch and continuously stirred tank reactors. In reducing conditions (PO2<10-6 bar), a strong inhibitory effect was observed. Solid characterization (XRD and SEM) suggested that precipitation of MnCO3 may have limited the exposure of UO2 surface sites to trace level oxidants. In contrast, a promotional effect of Mn(II) on UO2 dissolution was observed under moderate (PO2=0.01 bar) and fully oxic (PO2=0.21 bar) conditions. There may be a threshold concentration of Mn(II) above which either its inhibitory or promotional effect would not further increase. Compared with those of non-redox-active cations, the effects of Mn(II) on UO2 dissolution may be more complex and dependent on redox conditions.

Different effects of Mn(II) on UO<sub>2</sub> dissolution kinetics under reducing and oxidizing conditions

245th National Meeting (2013)

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Different effects of Mn(II) on UO2 dissolution kinetics under reducing and oxidizing conditions

Different effects of Mn(II) on UO₂ dissolution kinetics under reducing and oxidizing conditions