Effect of Manganese Oxide Aging and Structure Transformation on the Kinetics of Thiol Oxidation
| Autor: | Martial Taillefert, Shiliang Zhao, Eryn M. Eitel, Yuanzhi Tang |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
chemistry.chemical_classification
Inorganic chemistry Kinetics chemistry.chemical_element Oxides General Chemistry 010501 environmental sciences engineering.material 010502 geochemistry & geophysics 01 natural sciences Sulfur Redox Chemical kinetics Electron Transport chemistry Manganese Compounds Thiol engineering Environmental Chemistry Cryptomelane Reactivity (chemistry) Oxidation-Reduction 0105 earth and related environmental sciences Cysteine |
| Zdroj: | Environmental sciencetechnology. 52(22) |
| ISSN: | 1520-5851 |
| Popis: | 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 δ-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 δ-MnO2 was investigated with cysteine and compared to that of manganite, a Mn(III) oxyhydroxide phase. The reactivity of aged δ-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 δ-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. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|