Biodegradation of Uranium−Citrate Complexes:  Implications for Extraction of Uranium from Soils

Citrate is often used as a complexing agent to mobilize sorbed and precipitated uranium in both in situ and ex situ extraction of soils and nuclear reactor components. The biodegradability of U−citrate complexes is an important control over the potential migration of residual uranium after the extra...

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Bibliographic Details
Published in:Environmental science & technology 1998-02, Vol.32 (3), p.379-382
Main Authors: Huang, Frank Y. C, Brady, Patrick V, Lindgren, Eric R, Guerra, Peter
Format: Article
Language:English
Subjects:
Agents
Applied sciences
BACTERIA
Biodegradation
Biological and medical sciences
Biomass
Biotechnology
Carboxylic acids
CITRATE
CITRATES
CITRATOS
Decontamination. Miscellaneous
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Environment and pollution
EVOLUCION
EVOLUTION
Exact sciences and technology
Extraction
FLORA DEL SUELO
FLORE DU SOL
Fundamental and applied biological sciences. Psychology
Industrial applications and implications. Economical aspects
Miscellaneous
pH effects
Pollution
Pollution, environment geology
Radioactive wastes
Soil and sediments pollution
SOIL FLORA
Soils
SPECIATION
Uranium
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Summary:Citrate is often used as a complexing agent to mobilize sorbed and precipitated uranium in both in situ and ex situ extraction of soils and nuclear reactor components. The biodegradability of U−citrate complexes is an important control over the potential migration of residual uranium after the extraction process is complete. In solutions buffered at pH 6−7, limited biodegradation of citrate is observed within 10 days with initial U:citrate molar ratios ranging from 1:2 to 1:8; however, over 99% of the citrate is biodegraded rapidly at pH 8−9. The increase of pH may have shifted the equilibrium speciation of uranium from (UO2−citrate)2 2- to (UO2)3(OH)7 1- and, consequently, raised the bioavailability of citrate. At pH 6−7, a significant amount of uranium is also observed to associate with biomass, whereas only a negligible amount is observed at pH 8−9. Our experimental results suggest that the residual concentration of uranium−citrate complexes left in the treated soils can be reduced rapidly if the soil water pH is held between 8 and 9 after the extraction processes.
ISSN:0013-936X
1520-5851
DOI:10.1021/es970181d