Mechanism and Kinetics of Dark Iron Redox Transformations in Previously Photolyzed Acidic Natural Organic Matter Solutions
Mechanism and Kinetics of Dark Iron Redox Transformations in Previously Photolyzed Acidic Natural Organic Matter Solutions
复制标题
DOI：
10.1021/es3035889
复制
发表时间：
2013-02-19
影响因子：
11.4
通讯作者：
Waite, T. David
中科院分区：
文献类型：
--
作者：
Garg, Shikha;Ito, Hiroaki;Waite, T. David
苏万尼河黄腐酸 (SRFA) 辐照产生的稳定有机物质被证明是酸性 pH 值水溶液中 Fe(II) 的重要氧化剂，其速率常数远大于相同条件下 Fe(II) 氧化的速率常数。这些 Fe(II) 氧化物质是在光解过程中通过超氧化物介导的对 SRFA 中固有存在的还原有机部分的氧化而形成的，它们在黑暗中寿命很长，但在辐照条件下容易被单线态氧 (102) 快速氧化。内在的还原有机物质能够在酸性 pH 条件下还原 Fe(III)。尽管有机 Fe(II) 氧化剂和有机 Fe(III) 还原剂的确切身份尚不清楚，但它们的行为分别与半醌和类氢醌部分的预期一致。开发了一个动力学模型，该模型充分描述了所获得的实验数据的各个方面，并且能够预测在先前光解的天然有机物存在的情况下暗 Fe(II) 氧化速率和 Fe(III) 还原速率。
Stable organic species produced on irradiation of Suwannee River Fulvic Acid (SRFA) are shown to be important oxidants of Fe(II) in aqueous solutions at acidic pH, with rate constants substantially larger than those for oxygenation of Fe(II) under the same conditions. These Fe(II)-oxidizing species, which are formed during photolysis by superoxide-mediated oxidation of reduced organic moieties that are present intrinsically in SRFA, are long-lived in the dark but prone to rapid oxidation by singlet oxygen (102) under irradiated conditions. The intrinsic reduced organic species are able to reduce Fe(III) at acidic pH. Although the exact identities of the organic Fe(II) oxidant and the organic Fe(III) reductant are unclear, their behavior is consistent with that expected of semiquinone and hydroquinone-like moieties respectively. A kinetic model is developed that adequately describes all aspects of the experimental data obtained, and which is capable of predicting dark Fe(II) oxidation rates and Fe(III) reduction rates in the presence of previously photolyzed natural organic matter.