Effect of Manganese Oxide Aging and Structure Transformation on the Kinetics of Thiol Oxidation
Effect of Manganese Oxide Aging and Structure Transformation on the Kinetics of Thiol Oxidation
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DOI：
10.1021/acs.est.8b03993
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发表时间：
2018-11-20
影响因子：
11.4
通讯作者：
Taillefert, Martial
中科院分区：
文献类型：
--
作者：
Eitel, Eryn M.;Zhao, Shiliang;Taillefert, Martial
锰氧化物在环境相关条件下进行动态结构转化的硫醇氧化动力学和机理尚不清楚。在这项研究中，使用伏安微电极在pH 7.0下，同时测定了四种常见硫醇（半胱氨酸、同型半胱氨酸、半胱氨酸和谷胱甘肽）与新鲜和陈化的delta-MnO2相互作用时的硫醇/二硫对浓度。反应动力学对硫醇是一级反应，对锰氧化物是零级反应。在反应过程中观察到的瞬态中间硫表面物质为涉及两个连续的单电子转移步骤的机制提供了证据。研究了新鲜和陈化δ - mno2与半胱氨酸的反应动力学，并与锰（Mn(III)）氢氧化物相的反应动力学进行了比较。老化的delta-MnO2的反应活性由于结构转变为隐黑烷而下降，但仍高于锰矿，这表明瞬态表面中间体Mn（III）在促进delta-MnO2和隐黑烷中Mn（IV）的还原方面的潜在作用（与锰矿中的Mn（III）相比）。该研究证明了将锰氧化物矿物结构与氧化还原反应性相关联的重要性，并扩展了沉积环境中常见的硫醇在异化锰还原过程中用作电子穿梭体的潜力。
The kinetics and mechanism of thiol oxidation by Mn oxides undergoing dynamic structural transformation under environmentally relevant conditions remain poorly understood. In this study, thiol/disulfide pair concentrations were simultaneously determined in situ using voltammetric microelectrodes during the interaction of four common thiols (cysteine, homocysteine, cysteamine, and glutathione) with fresh and aged delta-MnO2 at pH 7.0. The reaction kinetics was first order with respect to thiol and zero order with respect to Mn oxides. A transient intermediate sulfur surface species observed during the reaction provides evidence for a mechanism involving two successive one-electron transfer steps. The reaction kinetics of fresh and aged delta-MnO2 was investigated with cysteine and compared to that of manganite, a Mn(III) oxyhydroxide phase. The reactivity of aged delta-MnO2 decreased as a result of structural transformation to cryptomelane but remained higher than that of manganite, suggesting the potential roles of transient Mn(III) surface intermediate in promoting the reduction of Mn(IV) in delta-MnO2 and cryptomelane (compared to Mn(III) in manganite). This study demonstrates the importance of correlating Mn oxide mineral structure and redox reactivity and extends the potential for thiols commonly found in sedimentary environments to be utilized as electron shuttles during dissimilatory Mn reduction.