Effects of Fe(II) and hydrogen peroxide interaction upon dissolving U02 under geologic repository conditions
Effects of Fe(II) and hydrogen peroxide interaction upon dissolving U02 under geologic repository conditions
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DOI：
10.1021/es040034x
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发表时间：
2005-01-01
影响因子：
11.4
通讯作者：
Betti, M
中科院分区：
文献类型：
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作者：
Amme, M;Bors, W;Betti, M
铁的氧化还原循环被认为是控制二氧化铀乏燃料地质处置库近场地球化学边界条件的主要机制之一。研究了过氧化氢（H2 O2）与铁（Fe 2 +/Fe 3+）反应对二氧化铀溶解的影响。在无氧间歇式反应器试验中，使反应伙伴与二氧化铀接触。当反应物浓度相等时，在不存在UO 2的情况下的相互作用给出了Fe 2+和H2 O2的化学计量的氧化还原反应。H_2O_2的优势导致其延迟催化分解。在UO 2存在的情况下，其溶解受缓慢机制（缺氧环境的典型机制）或过氧化铀沉淀的控制，这在很大程度上取决于反应物的比例。暴露于H2 O2后在UO 2表面上检测到过氧化铀（UO4.nH（2）O，m-studtite），但在暴露于化学计量的Fe（II）/H2 O2比溶液的表面上没有发现。这表明，H2 O2在氧化还原反应中是失活的，然后才形成UO 4。采用自旋捕获技术的ESR测量显示在反应开始后的最初几分钟内仅DMPO-OH加合物（OH的高初始浓度）。radical）;然而，在Fe（II）和H2 O2在10（-4）mol/L下与UO 2反应的情况下，溶解氧和Fe 2+浓度表明进一步的Fe中间体的参与，因此，芬顿氧化还原活性。
Iron redox cycling is supposed to be one of the major mechanisms that control the geochemical boundary conditions in the near field of a geologic repository for UO2 spent nuclear fuel. This work investigates the impact of reactions between hydrogen peroxide (H2O2) and iron (Fe2+/Fe3+) on UO2 dissolution. The reaction partners were contacted with UO2 in oxygen-free batch reactor tests. The interaction in absence of UO2 gives a stoichiometric redox reaction of Fe2+ and H2O2 when the reactants are present in equal concentration. Predomination of H2O2 results in its delayed catalytic decomposition. With UO2 present, its dissolution is controlled by either a slow mechanism (as typical for anoxic environments) or uranium peroxide precipitation, depending strongly on the reactant ratio. Uranium peroxide (UO4.nH(2)O, m-studtite), detected on UO2 surfaces after exposure to H2O2, was not found on the surfaces exposed to solutions with stoichometric Fe(II)/ H2O2 ratios. This suggests that H2O2 was deactivated in redox reactions before a formation of UO4 took place. ESR measurements employing the spin trapping technique revealed only the DMPO-OH adduct within the first minutes after the reaction start (high initial concentrations of the OH. radical); however, in the case of Fe(II) and H2O2 reacting at 10(-4) mol/L with UO2, dissolved oxygen and Fe2+ concentrations indicate the participation of further Fe intermediates and, therefore, Fenton redox activities.