Oxidative Remobilization of Biogenic Uranium (IV) Precipitates: Effects of Iron (II) and pH
The oxidative dissolution of biogenic U(IV) precipitates was investigated in bioreduced sediment suspensions in contact with atmospheric O2 with an emphasis on the influence of Fe(II) and pH on the rate and extent of U release from the solid to the aqueous phase. The sediment was collected from the US Department of Energy (DOE) Field Research Center (FRC) site at Oak Ridge, Tennessee. Biogenic U(IV) precipitates and bioreduced sediment were generated through anaerobic incubation with a dissimilatory metal reducing bacterium Shewanella putrefaciens strain CN32. The oxidative dissolution of freshly prepared and aged biogenic U(IV) was conducted in 0.1 mol/L NaNO3 electrolyte with variable pH and Fe(II) concentrations. Biogenic U(IV)O2(s) was oxidized with the highest rate and extent at pH 4 and 9. U release to the aqueous phase was the lowest at circumneutral pH. Increasing Fe(II) significantly decreased the release of U(VI) to the aqueous phase. From 70 to 100% of the U in the sediments was extractable at the experiment termination (40-80 days) with a bicarbonate solution (0.2 mol/L), indicating that biogenic U(IV) was oxidized regardless of Fe(II) concentration and pH. Sorption experiments and modeling calculations indicated that the inhibitive effect of Fe(II) on U(IV) oxidative remobilization was consistent with the Fe(III) oxide precipitation and U(VI) sorption to this secondary phase.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 876878
- Report Number(s):
- PNNL-SA-42839; 4592; KP1301010
- Journal Information:
- Journal of Environmental Quality, Journal Name: Journal of Environmental Quality Journal Issue: 5 Vol. 34; ISSN JEVQAA; ISSN 0047-2425
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
ACID CARBONATES
CATALYTIC EFFECTS
DISSOLUTION
Environmental Molecular Sciences Laboratory
GEOCHEMISTRY
IRON
OXIDATION
PH VALUE
SEDIMENTS
SORPTION
URANIUM COMPOUNDS
uranium geochemistry
oxidation
remobilization
immobilization
Fe(II) inhibition