Formation of free radicals by direct photolysis of halogenated phenols (HPs) and effects of DOM: A case study on monobromophenols
Formation of free radicals by direct photolysis of halogenated phenols (HPs) and effects of DOM: A case study on monobromophenols
复制标题
卤代酚 (HP) 直接光解形成自由基以及 DOM 的影响：以一溴酚为例
DOI：
10.1016/j.jhazmat.2020.122220
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发表时间：
2020
影响因子：
13.6
通讯作者：
Qu Baocheng
中科院分区：
文献类型：
--
作者：
Jiang Jingqiu;Zhao Hongxia;Xia Deming;Li Xintong;Qu Baocheng
自由基对于理解有机污染物的直接/间接转化机制具有重要作用。然而，很少有人努力阐明直接光解产生的自由基。采用电子顺磁共振（EPR）技术研究了模拟太阳光照射下卤代酚类化合物（HPs）的短寿命自由基。结果表明，HPs直接辐照产生三种自由基：碳中心自由基（dotC自由基）、氢自由基（dotH自由基）和羟基自由基（dotOH自由基）。与其他取代基相比，对位卤代取代基的生成量最高，这与密度泛函理论计算的能量一致。通过对反应物种和相应中间产物的分析，初步探讨了这些自由基的反应途径。溶解性有机物（DOM）通过直接影响自由基的生成，主要是通过生成受激三重态DOM（3DOM*）来促进HPs的光降解。不同DOM的水化电子浓度与稳定态3DOM * 之间存在正相关关系。我们的研究结果提供了深入了解环境光化学命运的HPs通过其直接光解，将有助于更准确地了解其在环境中的光转化机制。
The free radicals play an important role to understand direct/indirect transformation mechanisms of organic pollutants. However, very few efforts have been made to elucidate the radicals produced by direct photolysis. In this study, the short-lived radicals generated under simulated sunlight irradiation from representative halogenated phenols (HPs), monobromophenols, were investigated by electron paramagnetic resonance (EPR). The results showed that three radicals, carbon-centered radical (radical dotC), hydrogen radical (radical dotH) and hydroxyl radical (radical dotOH), were generated from the direct irradiation of HPs. Compared to other substitutions, halogenated atom atpara-position led to the highest production of these radicals which is in accordance with the energies calculated by density functional theory. Based on the analyses of the reactive species and corresponding intermediate adducts, the possible reaction pathways for these radicals were tentatively proposed. Dissolved organic matters (DOM) could enhance the photodegradation of HPs by directly affecting the radicals’ formation, mainly due to generation of excited triplet DOM (3DOM*). A positive correlation was found between the concentrations of hydrated electron and the steady state3DOM* from different DOM. Our findings provided insights into environmental photochemical fate of HPs through their direct photolysis and will help more accurately understand their phototransformation mechanisms in the environment.