Process-based modeling of arsenic(III) oxidation by manganese oxides under circumneutral pH conditions.
Process-based modeling of arsenic(III) oxidation by manganese oxides under circumneutral pH conditions.
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DOI：
10.1016/j.watres.2020.116195
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发表时间：
2020-07
期刊：
影响因子：
12.8
通讯作者：
B. Rathi;James Jamieson;Jing Sun;A. Siade;M. Zhu;O. Cirpka;H. Prommer
中科院分区：
文献类型：
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作者：
B. Rathi;James Jamieson;Jing Sun;A. Siade;M. Zhu;O. Cirpka;H. Prommer
大量实验研究已经确定了控制锰 (Mn) 氧化物氧化亚砷酸盐 (As(III)) 的多步反应机制。这些研究强调了边缘位点和中间过程的重要性，例如反应产物的表面钝化。然而，已确定的反应机制和控制因素很少在定量背景下进行评估。在这项研究中，开发了一个基于过程的建模框架来描述和量化影响锰氧化物氧化 As(III) 的不同过程的相对贡献和速率。模型开发和参数化受到文献研究中实验观察的限制，该文献研究涉及使用间歇式和搅拌流反应器在中性 pH 值下与环境相关的锰氧化物。我们的建模结果强调了过渡相的重要性，这仅在搅拌流实验中显而易见，其中 As(III) 氧化逐渐从快速反应的 Mn(IV) 边缘位置转移到缓慢反应的 Mn(III) 边缘位点。这些边缘位点的相对丰度是控制氧化速率的最重要因素，而表面钝化仅在搅拌流实验中限制氧化。 Mn(III) 边缘位点被证明在氧化中发挥着至关重要的作用，因此在控制 As 的长期命运方面发挥着至关重要的作用。这项研究加深了人们对氧化锰反应性以及氧化还原敏感金属（类）在环境中循环的重要性的理解。
Numerous experimental studies have identified a multi-step reaction mechanism to control arsenite (As(III)) oxidation by manganese (Mn) oxides. The studies highlighted the importance of edge sites and intermediate processes, e.g., surface passivation by reaction products. However, the identified reaction mechanism and controlling factors have rarely been evaluated in a quantitative context. In this study, a process-based modeling framework was developed to delineate and quantify the relative contributions and rates of the different processes affecting As(III) oxidation by Mn oxides. The model development and parameterization were constrained by experimental observations from literature studies involving environmentally relevant Mn oxides at circumneutral pH using both batch and stirred-flow reactors. Our modeling results highlight the importance of a transitional phase, solely evident in the stirred-flow experiments, where As(III) oxidation gradually shifts from fast reacting Mn(IV) to slowly reacting Mn(III) edge sites. The relative abundance of these edge sites was the most important factor controlling the oxidation rate, whereas surface passivation restricted oxidation only in the stirred-flow experiment. The Mn(III) edge sites were demonstrated to play a crucial role in the oxidation and therefore in controlling the long-term fate of As. This study provided an improved understanding of Mn oxide reactivity and the significance in the cycling of redox-sensitive metal(loid)s in the environment.