Application of surfactant modified montmorillonite with different conformation for photo-treatment of perfluorooctanoic acid by hydrated electrons
Application of surfactant modified montmorillonite with different conformation for photo-treatment of perfluorooctanoic acid by hydrated electrons
复制标题
不同构象表面活性剂改性蒙脱石在水合电子光处理全氟辛酸中的应用
DOI：
10.1016/j.chemosphere.2019.07.032
复制
发表时间：
2019-11-01
期刊：
影响因子：
8.8
通讯作者：
Gu, Cheng
中科院分区：
文献类型：
--
作者：
Chen, Zhanghao;Tian, Haoting;Gu, Cheng
全氟烷基和多氟烷基物质（PFASs）是一类具有高生物蓄积性和高毒性的高度持久性污染物。我们前期的研究表明，在有机蒙脱土/吲哚乙酸（IAA）体系中，全氟辛酸（PFOA）在紫外照射下可以完全脱氟。然而，目前对其降解机理和废水处理试验的研究还很缺乏。在此，我们系统地研究了不同有机蒙脱石存在下的脱氟反应，发现降解过程明显受表面活性剂构型的控制。在十六烷基三甲基铵（HDTMA）改性蒙脱土中，HDTMA以倾斜构象和与水溶液隔离的粘土夹层存在，保护IAA光照射产生的水合电子不被氧猝灭。除氟加氢过程是主要的降解途径。而在聚-4-乙烯基吡啶-co-苯乙烯（PVPcoS）改性蒙脱土中，由于PVPcoS的多重电荷，预计会形成与粘土表面平行的平面构象。羟基自由基是由扩散到粘土夹层中的水合电子与氧分子反应产生的，也参与了降解过程。我们的研究结果进一步表明，混合改性蒙脱土可以结合两种改性的优点，因此即使在没有任何预处理的实际工业废水中也表现出优异的反应性。该技术在实际废水处理中具有很大的潜力。(C) 2019 Elsevier Ltd.版权所有。
Perfluoroallcyl and polyfluoroalkyl substances (PFASs) are a class of highly persistent contaminants with high bioaccumulation and toxicity. Our previous studies showed that perfluorooctanoic acid (PFOA) can be completely defluorinated under UV irradiation in organo-montmorillonite/indole acetic acid (IAA) system. However, there is still lack of information for the degradation mechanism and the test for wastewater treatment. Here, we systematically investigated the defluorination reaction in the presence of different organo-montmorillonites and found that the degradation process was apparently controlled by the configuration of surfactants. In hexadecyltrimethyl ammonium (HDTMA)-modified montmorillonite, HDTMA exists as a tilt conformation and isolated clay interlayer from the aqueous solution, protecting hydrated electrons generated by photo-irradiation of IAA from quenching by oxygen. Defluorination hydrogenation process was the dominant degradation pathway. While in poly-4-vinylpyridine-co-styrene (PVPcoS)-modified montmorillonite, due to the multiple charges of PVPcoS, a flat conformation parallel to clay surface was expected. Hydroxyl radicals, which were generated by the reaction of hydrated electrons with oxygen molecules diffused into clay interlayer, are also involved in the degradation process. Our results further demonstrate that mixture modified montmorillonite could combine the advantages of both modifications, thus showing superior reactivity even for actual industrial wastewater without any pretreatment. This technique would have great potential for treatment of actual wastewater. (C) 2019 Elsevier Ltd. All rights reserved.