H3AsO3-CO32- / HCO3--H2O系统中羟基自由基催化氧化砷的内在机理：量子化学研究。,Chemosphere

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H3AsO3-CO32- / HCO3--H2O系统中羟基自由基催化氧化砷的内在机理：量子化学研究。
Chemosphere ( IF 8.1 ) Pub Date : 2019-08-05 , DOI: 10.1016/j.chemosphere.2019.124466
A N Masliy ₁ , A M Kuznetsov ₁ , G V Korshin ₂

Affiliation

砷是一种剧毒的化合物，存在于世界各地的许多水源中。从水中去除亚砷酸盐需要将其氧化成砷酸盐，这更适合使用公认的技术进行处理。先前的研究表明，在碳酸根离子的存在下，亚砷酸盐被羟基自由基的氧化作用显着加速，但尚未建立起加速作用的内在机理。本工作的主要目的是在密度泛函理论的框架下研究砷的氧化，建立详细的微观水平的砷与羟基自由基相互作用的机理，并阐明碳酸根离子催化作用的性质。这项研究的结果表明，[As（OH）2CO3]-络合物是在H3AsO3-CO32- / HCO3--H2O系统中形成的热力学最稳定的物种。羟基与[As（OH）2CO3]-配合物的相互作用在亚砷酸盐的后续氧化反应中产生了预反应配合物[As（OH）3CO3]-*。反应物的结构，产物和过渡态以及反应前和反应后的配合物，对应于在不存在和不存在的情况下使用羟基自由基将第一阶段As（III）氧化为As（IV）中间体的几种可能机理。在这项研究中确定[As（OH）2CO3]-的存在。数据表明，亚砷酸盐-碳酸盐络合物[As（OH）2CO3]-的特征是在羟基自由基的作用下，第一氧化阶段的活化能明显较低（2。

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The intrinsic mechanism of catalytic oxidation of arsenite by hydroxyl-radicals in the H3AsO3-CO32-/HCO3--H2O system: A quantum-chemical examination.

Arsenite is a highly toxic compound present in many water sources around the world. The removal of arsenite from water requires its oxidation to arsenate which is much more amenable to treatment using well attested technologies. Prior research has shown that the oxidation of arsenite by hydroxyl radicals is significantly accelerated in the presence of carbonate ions but the intrinsic mechanisms of the acceleration have not yet been established. The main goal of the present work was to examine the oxidation of arsenite in the framework of the density functional theory, to establish a detailed microscopic level mechanism of interactions between arsenite and hydroxyl radicals and to elucidate the nature of the catalytic effect of carbonate ions. Results of this study demonstrate that the [As(OH)2CO3]- complex is the thermodynamically most stable species formed in the system H3AsO3-CO32-/HCO3--H2O. Interactions of the hydroxyl radical with the [As(OH)2CO3]- complex yield the pre-reaction complex [As(OH)3CO3]-∗ in the reaction of subsequent oxidation of arsenite. The structures of the reactants, products and transition states, as well as pre- and post-reaction complexes corresponding to several possible mechanisms of the first stage of As(III) oxidation to As(IV) intermediate using hydroxyl radicals in the absence and in the presence of [As(OH)2CO3]-, were determined in this study. The data demonstrate that the arsenite-carbonate complexes [As(OH)2CO3]- are characterized by a significantly lower activation energy of the first oxidation stage under the action of a hydroxyl radical (2.8 kcal/mol) compared to that for the free arsenite H3AsO3 (13.6 kcal/mol).

更新日期：2019-08-05

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