Effects of Mn(II) on UO2 dissolution under anoxic and oxic conditions

Zimeng Wang, Bradley M. Tebo, Daniel E. Giammar

    Research output: Contribution to journalArticlepeer-review

    35 Scopus citations

    Abstract

    Groundwater composition and coupled redox cycles can affect the long-term stability of U(IV) products from bioremediation. The effects of Mn(II), a redox active cation present at uranium-contaminated sites, on UO2 dissolution in both oxic and anoxic systems were investigated using batch and continuous-flow reactors. Under anoxic conditions Mn(II) inhibited UO 2 dissolution, which was probably due to adsorption of Mn(II) and precipitation of MnCO3 that decreased exposure of U(IV) surface sites to oxidants. In contrast, Mn(II) promoted UO2 dissolution under oxic conditions through Mn redox cycling. Oxidation of Mn(II) by O2 produced reactive Mn species, possibly short-lived Mn(III) in solution or at the surface, that oxidatively dissolved the UO2 more rapidly than could the O2 alone. At pH 8 the Mn cycling was such that there was no measurable accumulation of particulate Mn oxides. At pH 9 Mn oxides could be produced and accumulate, while they were continuously reduced by UO2, with Mn(II) returning to the aqueous phase. With the rapid turnover of Mn in the redox cycle, concentrations of Mn as low as 10 μM could maintain an enhanced UO2 dissolution rate. The presence of the siderophore desferrioxamine B (a strong Mn(III)-complexing ligand) effectively decoupled the redox interactions of uranium and manganese to suppress the promotional effect of Mn(II).

    Original languageEnglish (US)
    Pages (from-to)5546-5554
    Number of pages9
    JournalEnvironmental Science and Technology
    Volume48
    Issue number10
    DOIs
    StatePublished - May 20 2014

    ASJC Scopus subject areas

    • General Chemistry
    • Environmental Chemistry

    Fingerprint

    Dive into the research topics of 'Effects of Mn(II) on UO2 dissolution under anoxic and oxic conditions'. Together they form a unique fingerprint.

    Cite this