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Electrochemical Advanced Oxidation of Perfluorooctanoic Acid: Mechanisms and Process Optimization with Kinetic Modeling
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2022-09-29 , DOI: 10.1021/acs.est.2c02906
Zefang Chen 1 , Xiaojun Wang 2 , Hualiang Feng 2 , Shaohua Chen 2 , Junfeng Niu 3 , Guanglan Di 4 , David Kujawski 5 , John C Crittenden 1
Affiliation  

Electrochemical advanced oxidation processes (EAOPs) are promising technologies for perfluorooctanoic acid (PFOA) degradation, but the mechanisms and preferred pathways for PFOA mineralization remain unknown. Herein, we proposed a plausible primary pathway for electrochemical PFOA mineralization using density functional theory (DFT) simulations and experiments. We neglected the unique effects of the anode surface and treated anodes as electron sinks only to acquire a general pathway. This was the essential first step toward fully revealing the primary pathway applicable to all anodes. Systematically exploring the roles of valence band holes (h+), hydroxyl radicals (HO), and H2O, we found that h+, whose contribution was previously underestimated, dominated PFOA mineralization. Notably, the primary pathway did not generate short-chain perfluoroalkyl carboxylic acids (PFCAs), which were previously thought to be the main degradation intermediates, but generated other polyfluorinated alkyl substances (PFASs) that were rapidly degraded upon formation. Also, we developed a simplified kinetic model, which considered all of the main processes (mass transfer with electromigration included, surface adsorption/desorption, and oxidation on the anode surface), to simulate PFOA degradation in EAOPs. Our model can predict PFOA concentration profiles under various current densities, initial PFOA concentrations, and flow velocities.

中文翻译:

全氟辛酸的电化学高级氧化:动力学建模的机理和工艺优化

电化学高级氧化工艺 (EAOPs) 是全氟辛酸 (PFOA) 降解的有前景的技术,但 PFOA 矿化的机制和首选途径仍然未知。在此,我们使用密度泛函理论 (DFT) 模拟和实验提出了一种可行的 PFOA 电化学矿化主要途径。我们忽略了阳极表面的独特影响,将阳极视为电子沉,只是为了获得一般路径。这是全面揭示适用于所有阳极的主要途径的重要第一步。系统探索价带空穴(h +)、羟基自由基(HO )和H 2 O 的作用,我们发现h +,其贡献以前被低估,主导 PFOA 矿化。值得注意的是,主要途径不会产生以前被认为是主要降解中间体的短链全氟烷基羧酸(PFCA),而是产生其他多氟烷基物质(PFAS),这些物质在形成时会迅速降解。此外,我们开发了一个简化的动力学模型,该模型考虑了所有主要过程(包括电迁移的传质、表面吸附/解吸和阳极表面的氧化),以模拟 EAOP 中的 PFOA 降解。我们的模型可以预测各种电流密度、初始 PFOA 浓度和流速下的 PFOA 浓度分布。
更新日期:2022-09-29
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