Oxidative UO2 dissolution induced by soluble Mn(III).
Oxidative UO2 dissolution induced by soluble Mn(III).
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DOI：
10.1021/es4037308
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发表时间：
2014-01
影响因子：
11.4
通讯作者：
Zimeng Wang;W. Xiong;B. Tebo;D. Giammar
中科院分区：
文献类型：
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作者：
Zimeng Wang;W. Xiong;B. Tebo;D. Giammar
二氧化铀的稳定性是铀还原生物修复成功的关键。当还原条件不再维持时，Mn氧化还原循环可催化介导UO 2的氧化和铀的再活化。配体稳定的可溶性Mn（III）是Mn地球化学循环中重要的氧化还原活性中间体。本研究评价了由焦磷酸盐（PP）和去铁胺B（DFO B）稳定的可溶性Mn（III）氧化溶解UO 2的动力学。的Mn（III）-PP复合物是一种有效的氧化剂，诱导快速二氧化铀溶解的速率高于溶解O2的可比浓度。然而，Mn（III）-DFOB复合物不能诱导二氧化铀的氧化溶解。Mn（III）配合物氧化UO 2的能力可能取决于Mn（III）与配体的配位是否允许配合物附着在UO 2表面以促进电子转移。通过Mn（III）-PP络合物对UO 2氧化溶解动力学的系统研究表明，Mn（III）可以直接氧化UO 2，而不涉及颗粒状Mn物质（例如，MnO 2）。观察到Mn（III）和UO 2之间的预期2：1反应化学计量。可溶性Mn（III）在氧化二氧化铀的反应性较高，在较低的比例焦磷酸锰（III）和较低的pH值，这可能是有关的配体-金属比和/或质子化状态的Mn（III）-焦磷酸盐络合物的差异。Mn（III）-PP在pH 9.0时发生歧化反应，然后由MnO 2和可溶性Mn（III）共同驱动UO 2的氧化。动力学模型推导出的实验结果提供了很好的拟合。
The stability of UO2 is critical to the success of reductive bioremediation of uranium. When reducing conditions are no longer maintained, Mn redox cycling may catalytically mediate the oxidation of UO2 and remobilization of uranium. Ligand-stabilized soluble Mn(III) was recently recognized as an important redox-active intermediate in Mn biogeochemical cycling. This study evaluated the kinetics of oxidative UO2 dissolution by soluble Mn(III) stabilized by pyrophosphate (PP) and desferrioxamine B (DFOB). The Mn(III)-PP complex was a potent oxidant that induced rapid UO2 dissolution at a rate higher than that by a comparable concentration of dissolved O2. However, the Mn(III)-DFOB complex was not able to induce oxidative dissolution of UO2. The ability of Mn(III) complexes to oxidize UO2 was probably determined by whether the coordination of Mn(III) with ligands allowed the attachment of the complexes to the UO2 surface to facilitate electron transfer. Systematic investigation into the kinetics of UO2 oxidative dissolution by the Mn(III)-PP complex suggested that Mn(III) could directly oxidize UO2 without involving particulate Mn species (e.g., MnO2). The expected 2:1 reaction stoichiometry between Mn(III) and UO2 was observed. The reactivity of soluble Mn(III) in oxidizing UO2 was higher at lower ratios of pyrophosphate to Mn(III) and lower pH, which is probably related to differences in the ligand-to-metal ratio and/or protonation states of the Mn(III)-pyrophosphate complexes. Disproportionation of Mn(III)-PP occurred at pH 9.0, and the oxidation of UO2 was then driven by both MnO2 and soluble Mn(III). Kinetic models were derived that provided excellent fits of the experimental results.