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首页> 外文期刊>Geochimica et Cosmochimica Acta: Journal of the Geochemical Society and the Meteoritical Society >pH-dependence of production of oxidants (Cu( III) and/or HO center dot) by copper-catalyzed decomposition of hydrogen peroxide under conditions typical of natural saline waters
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pH-dependence of production of oxidants (Cu( III) and/or HO center dot) by copper-catalyzed decomposition of hydrogen peroxide under conditions typical of natural saline waters

机译：通过在天然盐水水的典型条件下通过铜催化分解氧化剂（Cu（III）和/或HO中心点）的pH依赖性

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The oxidation and reduction kinetics of copper in natural aquatic systems determines its prevailing redox state, with implication to its toxicity, bioavailability and solubility. When reduced copper(I) co-occurs with ubiquitous hydrogen peroxide (H2O2), their reaction forms an oxidizing intermediate able to affect redox transformation of copper, other transition metals and organic carbon. In this work the kinetics and mechanism of reactions of nanomolar concentrations of copper (Cu) with H2O2 in bicarbonate-buffered 0.7 M NaCl solutions over the pH range from 6.0 to 8.0 have been investigated and a kinetic model developed to assist in understanding the results obtained. While the rate of cuprous ion ( Cu(I)) peroxidation did not vary markedly with pH, the rates of both cupric ion (Cu(II)) reduction by H2O2 and the production of oxidative intermediates showed strong pH dependence with both rates observed to increase with increasing pH. The increasing proportion of H2O2 present as the hydroperoxyl anion (HO2-) with increasing pH plays an important role in these trends. However, in order to adequately describe the behavior observed, it is also necessary to invoke a pH-dependent intrinsic conditional rate constant for the reaction between Cu(II) and HO2-. The nature of the oxidants formed when Cu(I) is oxidized by H2O2 has been probed by measuring the hydroxylation of phthalhydrazide and the degradation of formate in the absence and presence of probe compounds with well-established reactivity toward hydroxyl radicals (HO center dot). The results obtained suggest that a higher oxidation state of copper, Cu(III), rather than HO center dot is the key oxidant formed over the pH range of 6.0-8.0. Simulations under conditions relevant to natural saline environments reveal that increase in pH results in acceleration in the H2O2-driven cycling of Cu between +I and +II oxidation states but does not significantly influence the rate of production of Cu(III) with important implicat
机译：天然水生系统中铜的氧化和减少动力学决定了其普遍的氧化还原状态，含义对其毒性，生物利用度和溶解性。当铜（I）用普遍的过氧化氢（H 2 O 2）共同发生时，它们的反应形成氧化中间体，能够影响铜，其它过渡金属和有机碳的氧化还原转化。在这项工作中，已经研究了碳酸氢盐缓冲的0.7M NaCl溶液中的铜（Cu）与H 2 O 2的铜（Cu）反应的动力学和机制已经研究了6.0-8.0的pH范围内，并开发了动力学模型，以协助了解所获得的结果。虽然亚富子离子（Cu（I））过氧化的速率没有明显与pH显着变化，但是通过H 2 O 2还原的铜离子（Cu（II））的速率和氧化中间体的产生表现出对观察到的两个速率的强烈pH依赖性增加pH值。随着氢过氧基阴离子（HO2-）的增加比例的增加与pH值增加在这些趋势中起重要作用。然而，为了充分描述观察到的行为，还需要调用Cu（II）和HO2-之间的反应的pH依赖性特性条件率常数。通过H 2 O 2氧化时形成的氧化剂的性质已经通过测量邻苯三酰肼的羟基化和甲酸甲酸甲酸的羟基化和探针化合物的较良好的羟基自由基的反应性（Ho中心点）进行。得到的结果表明，铜，Cu（III）的较高氧化状态，而不是HO中心点是在6.0-8.0的pH范围内形成的关键氧化剂。仿真在与天然盐水环境相关的条件下，揭示了PH的增加导致Cu与+ I和+ II氧化态的H2O2驱动循环的加速度增加，但不会显着影响Cu（III）的生产率与重要Impricat

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