Bacterial Siderophores Promote Dissolution of UO2 under Reducing Conditions
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- 作者：Scott W. Frazier ; Ruben Kretzschmar ; and Stephan M. Kraemer
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：August 1, 2005
- 年：2005
- 卷：39
- 期：15
- 页码：5709 - 5715
- 全文大小：146K
- 年卷期：v.39,no.15(August 1, 2005)
- ISSN：1520-5851
文摘
Tetravalent actinides are often considered environmentallyimmobile due to their strong hydrolysis and formationof sparingly soluble oxide phases. However, biogenic ligandscommonly found in the soil environment may increasetheir solubility and mobility. We studied the adsorption anddissolution kinetics of UO2 in the presence of a microbialsiderophore, desferrioxamine-B (DFO-B), under reducingconditions. Using batch and continuous flow stirred tankreactors (CFSTR), we found that DFO-B increases the solubilityof UIV and accelerates UO2 dissolution rates through a ligand-promoted dissolution mechanism. DFO-B adsorption toUO2 followed a Langmuir-type isotherm. The maximumadsorbed DFO-B concentrations were 3.3 
mol m-2 betweenpH 3 and 8 and declined above pH 8. DFO-B dissolvedUO2 at a DFO-B surface-saturated net rate of 64 nmol h-1m-2 (pH 7.5, I = 0.01 M) according to the first-orderrate equation R = kL[Lads], with a rate coefficient kL of0.019 h-1. Even at very low siderophore concentrations (e.g.1 M), net dissolution rates (16 nmol h-1 m-2, pH 7.5, I= 0.01 M) were substantially greater than net proton-promoteddissolution rates (3 nmol h-1 m-2, pH 7-7.5, I = 0.01 M).Interestingly, adding dissolved FeIII had negligible effects onDFO-B-promoted UO2 dissolution rates, despite its potentialas a competitor for DFO-B and as an oxidant of UIV.Our results suggest that strong organic ligands couldinfluence the environmental mobility of tetravalent actinidesand should be considered in predictions for nuclearwaste storage and remediation strategies.
mol m-2 betweenpH 3 and 8 and declined above pH 8. DFO-B dissolvedUO2 at a DFO-B surface-saturated net rate of 64 nmol h-1m-2 (pH 7.5, I = 0.01 M) according to the first-orderrate equation R = kL[Lads], with a rate coefficient kL of0.019 h-1. Even at very low siderophore concentrations (e.g.1 M), net dissolution rates (16 nmol h-1 m-2, pH 7.5, I= 0.01 M) were substantially greater than net proton-promoteddissolution rates (3 nmol h-1 m-2, pH 7-7.5, I = 0.01 M).Interestingly, adding dissolved FeIII had negligible effects onDFO-B-promoted UO2 dissolution rates, despite its potentialas a competitor for DFO-B and as an oxidant of UIV.Our results suggest that strong organic ligands couldinfluence the environmental mobility of tetravalent actinidesand should be considered in predictions for nuclearwaste storage and remediation strategies.