Bacterial siderophores promote dissolution of UO2 under reducing conditions
Bacterial siderophores promote dissolution of UO2 under reducing conditions
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DOI：
10.1021/es050270n
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发表时间：
2005-08-01
影响因子：
11.4
通讯作者：
Kraemer, SM
中科院分区：
文献类型：
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作者：
Frazier, SW;Kretzschmar, R;Kraemer, SM
四价锕系元素通常被认为是环境固定的，因为它们强烈的水解和形成微溶的氧化物相。然而，土壤环境中常见的生物配体可能会增加其溶解性和流动性。我们研究了还原条件下，在微生物铁载体，去铁胺-B（DIFO-B）的存在下，二氧化铀的吸附和溶解动力学。使用间歇式和连续流搅拌釜反应器（CFSTR），我们发现DFO-B增加了U-IV的溶解度，并通过配体促进的溶解机制加速UO 2的溶解速率。DFO-B对二氧化铀的吸附符合Langmuir型吸附等温线。最大吸附DFO-B浓度为3.3 μ mol m（-2）之间的pH值3和8和pH值8以上下降。根据一级速率方程R = k（L）[L-ads]，DFO-B溶解UO 2的表面饱和净速率为64 nmol h（-1）m（-2）（pH 7.5，/ = 0.01 M），速率系数k（L）为0.019 h（-1）。即使在非常低的铁载体浓度（例如1 μ M）下，净溶解速率（16 nmol h（-1）m（-2），pH 7.5，/ = 0.01 M）也基本上大于净质子促进的溶解速率（3 nmol h（-1）m（-2），pH 7-7.5，/ = 0.01 M）。有趣的是，添加溶解的Fe-III对DFO-B促进的UO 2溶解速率的影响可以忽略不计，尽管其作为DFO-B的竞争者和U-IV的氧化剂的潜力。我们的研究结果表明，强有机配体可能会影响四价锕系元素的环境流动性，并应考虑在预测核废料的存储和修复策略。
Tetravalent actinides are often considered environmentally immobile due to their strong hydrolysis and formation of sparingly soluble oxide phases. However, biogenic ligands commonly found in the soil environment may increase their solubility and mobility. We studied the adsorption and dissolution kinetics of UO2 in the presence of a microbial siderophore, desferrioxamine-B (DIFO-B), under reducing conditions. Using batch and continuous flow stirred tank reactors (CFSTR), we found that DFO-B increases the solubility of U-IV and accelerates UO2 dissolution rates through a ligand-promoted dissolution mechanism. DFO-B adsorption to UO2 followed a Langmuir-type isotherm. The maximum adsorbed DFO-B concentrations were 3.3 mu mol m(-2) between pH 3 and 8 and declined above pH 8. DFO-B dissolved UO2 at a DFO-B surface-saturated net rate of 64 nmol h(-1) m(-2) (pH 7.5, / = 0.01 M) according to the first-order rate equation R = k(L)[L-ads], with a rate coefficient k(L) of 0.019 h(-1). Even at very low siderophore concentrations (e.g. 1 mu M), net dissolution rates (16 nmol h(-1) m(-2), pH 7.5, / = 0.01 M) were substantially greater than net proton-promoted dissolution rates (3 nmol h(-1) m(-2), pH 7-7.5, / = 0.01 M). Interestingly, adding dissolved Fe-III had negligible effects on DFO-B-promoted UO2 dissolution rates, despite its potential as a competitor for DFO-B and as an oxidant of U-IV. Our results suggest that strong organic ligands could influence the environmental mobility of tetravalent actinides and should be considered in predictions for nuclear waste storage and remediation strategies.