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Kinetics of microbial reduction of Solid phase U(VI).
Chongxuan Liu1, Byong-Hun Jeon, John M Zachara
1Pacific Northwest National Laboratory, Richland, Washington 99352, USA. Chongxuan.liu@pnl.gov
Environmental Science & Technology
|November 24, 2006
Summary
Microbial reduction of solid uranium (U(VI)) by Shewanella oneidensis MR-1 is a complex process. It involves uranium dissolution, diffusion, and bacterial activity, influencing the overall bioreduction kinetics.
Area of Science:
- Geochemistry
- Microbiology
- Environmental Science
Background:
- Uranium (U(VI)) contamination poses environmental risks.
- Understanding microbial reduction of solid-phase U(VI) is crucial for remediation.
- Sodium boltwoodite is a relevant uranyl silicate mineral.
Purpose of the Study:
- To investigate the kinetics of microbial U(VI) reduction by Shewanella oneidensis MR-1.
- To elucidate the interplay between U(VI) dissolution, diffusion, and microbial activity.
- To model the coupled processes controlling solid-phase U(VI) bioreduction.
Main Methods:
- Utilized sodium boltwoodite as the solid-phase U(VI) source.
- Employed Shewanella oneidensis strain MR-1 as the dissimilatory metal-reducing bacterium (DMRB).
- Applied transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and laser-induced fluorescence spectroscopy (LIFS) for analysis.
Main Results:
- Solid-phase U(VI) dissolved and diffused from grain interiors before reduction.
- U(VI) reduction occurred on bacterial surfaces and/or within the periplasm.
- A coupled model incorporating dissolution, diffusion, and Monod kinetics accurately described the observed kinetics.
Conclusions:
- Microbial reduction of solid-phase U(VI) is a multifactorial process.
- Bicarbonate-promoted dissolution and intragrain uranyl diffusion are key factors.
- Coupled biological, chemical, and physical processes govern U(VI) bioreduction kinetics.
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