Reoxidation of Reduced Uranium with Iron(III) (Hydr)Oxides under Sulfate-Reducing Conditions
In cultures of Desulfovibrio desulfuricansG20 the effects of iron(III) (hydr)oxides (hematite, goethite, and ferrihydrite) on microbial reduction and reoxidation of uranium (U) were evaluated under lactate-limited sulfate-reducing conditions. With lactate present, G20 reduced U(VI) in both 1,4-piperazinediethanesulfonate (PIPES) and bicarbonate buffer. Once lactate was depleted, however, microbially reduced U served as an electron donor to reduce Fe(III) present in iron(III) (hydr)oxides. With the same initial amount of Fe(III) (10 mmol/L) for each iron(III) (hydr)oxide,reoxidation of U(IV) was greater with hematite than with goethite or ferrihydrite. As the initial mass loading of hematite increased from 0 to 20 mmol of Fe(III)/L, the rate and extent of U(IV) reoxidation increased. Subsequent addition of hematite [15 mmol of Fe(III)/L] to stationary-phase cultures containing microbially reduced U(IV) also resulted in rapid reoxidation to U(VI). Analysis by U L3-edge X-ray absorption near-edge spectroscopy (XANES) of microbially reduced U particles yielded spectra similar to that of natural uraninite. Observations by high-resolution transmission electron microscopy, selected area electron diffraction, and energy-dispersive X-ray spectroscopic analysis confirmed that precipitated U associated with cells was uraninite with particle diameters of 3-5 nm. By the same techniques, iron sulfide precipitates were found to have a variable Fe and S stoichiometry and were not associated with cells.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15020662
- Report Number(s):
- PNNL-SA-45281; KP1704020; KP1301010; KP1301010
- Journal Information:
- Environmental Science and Technology, 39(7):2059-2066, Journal Name: Environmental Science and Technology, 39(7):2059-2066
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ABSORPTION
ACID CARBONATES
BINDING ENERGY
DESULFOVIBRIO
ELECTRON DIFFRACTION
ELECTRONS
GOETHITE
HEMATITE
IRON SULFIDES
LACTATES
SPECTRA
SPECTROSCOPY
STOICHIOMETRY
TEM
TRANSMISSION ELECTRON MICROSCOPY
URANINITES
URANIUM
VALENCE
X-ray absorption spectroscopy
XANES
bacterial reduction
electron microscopy
hematite
iron oxide
remediation
sulfate-reducing bacteria
uranium reduction