Interfacial formation of environmentally persistent free radicals-A theoretical investigation on pentachlorophenol activation on montmorillonite in PM2.5.
Interfacial formation of environmentally persistent free radicals-A theoretical investigation on pentachlorophenol activation on montmorillonite in PM2.5.
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DOI：
10.1016/j.ecoenv.2018.11.041
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发表时间：
2019-03
影响因子：
6.8
通讯作者：
Wenxiao Pan;Jiamin Chang;Xian Liu;Q. Xue;Jianjie Fu;A. Zhang
中科院分区：
文献类型：
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作者：
Wenxiao Pan;Jiamin Chang;Xian Liu;Q. Xue;Jianjie Fu;A. Zhang
大气细颗粒物（PM2.5）中的环境持久性自由基（EPFRs）具有很高的生物活性，导致严重的健康问题。芳香族污染物在PM2.5的重要固体成分蒙脱土（MMT）上容易转化为epfr，是空气污染物向毒性更强的化学物质的激活，也是PM2.5中epfr的二次来源。本研究利用密度泛函理论（DFT）计算了空气污染中典型EPFR前体五氯酚（PCP）在Fe(III)-、Ca-和Na-MMT表面的界面反应。发现PCP分子在三个MMT表面被放热吸附。此外，由于Fe(III)-MMT中Fe3+的半填满的3位可以充当电子受体，使得电子从PCP中酚O的2位转移到Fe离子上，因此PCP向Fe离子发生了显著的电荷转移，并最终导致Fe(III)-MMT表面上形成表面结合的苯氧基自由基。然而，Ca-和Na-MMT表面没有类似的电荷转移，PCP转化反应在Ca-和Na-MMT表面受到阻碍。也就是说，在Ca-MMT和Na-MMT表面，PCP不可能活化到相应的EPFRs，而pm2.5中具有催化活性的Fe(III)-MMT可以在室温下将氯化苯酚转化为毒性更强的苯氧型EPFRs。因此，具有催化能力的MMT对PM2.5毒性的影响值得关注。
Environmentally persistent free radicals (EPFRs) in atmospheric fine particulate matters (PM2.5) possess high bioactivity and result in severe health problems. The facile transformation of aromatic pollutants into EPFRs on montmorillonite (MMT), an important solid component in PM2.5, is an activation of air pollutants into more toxic chemical species and also attributes to the secondary source of EPFRs in PM2.5. In this study, the interfacial reactions of pentachlorophenol (PCP), a typical EPFR precursor in air pollution, on the Fe(III)-, Ca- and Na-MMT surfaces have been explored by the density functional theory (DFT) calculations using the periodic slab models. The PCP molecule is found to be exothermically adsorbed on the three MMT surfaces. Moreover, significant charge transfer from PCP to Fe takes place and finally leads to the surface-bound phenoxyl radical formation on the Fe(III)-MMT surface since the half-filled3dorbital of Fe3+in Fe(III)-MMT could act as electron acceptor allowing the electron transferring from the2porbital of the phenolic O in PCP to Fe ion. However, similar charge transfer is not found in the Ca- and Na-MMTs, and the PCP transformation reaction is hindered on the Ca- and Na-MMT surfaces. Namely, the PCP activation to the corresponding EPFRs is impossible on the Ca-MMT and Na-MMT surfaces, while the catalytically active Fe(III)-MMT in PM2.5can transform the chlorinated phenols into more toxic phenoxy-type EPFRs at ambient temperatures. Accordingly, more attention should be paid on the effect of MMT with catalytical capacity on the toxicity of PM2.5.