Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Yunnan Institute of Environmental Science, Kunming 650034, China.
J Hazard Mater. 2018 Jun 15;352:172-181. doi: 10.1016/j.jhazmat.2018.03.045. Epub 2018 Mar 26.
Mechanochemical degradation (MCD) is a promising eco-friendly method to dispose persistent organic pollutants (POPs). Mechanically induced free-radical attack was thought to be one of the key elements in initiating and accelerating the dechlorination and degradation of POPs. In this study, mechanochemical formation of free-radicals and their roles in the remediation of hexachlorobenzene (HCB) contaminated soil were explored using both of experimental analysis and quantum chemical calculations. It was found that chlorinated phenoxy radicals(CB-O) can be produced in the milling process and they played a vital role in the dechlorination of HCB, based on the results of electron spin-resonance (ESR) and X-ray photoelectron spectra (XPS). Two transition states of mechanochemical reaction along the formation of pentachlorinated phenoxy radical (PeCB-O) were located, with the energy barriers of 39.4 and 3.4 kJ/mol. The localized orbital locator (LOL), Mayer bond order and topological analysis were also implemented to depict the process in detail. Free-radical attack dominated dechlorination pathway of HCB in the MCD process was also verified by the Fukui function analysis. The study on the mechanically-induced generation of free-radicals and their associated modes of action on the degradation of HCB will provide a deep insight into mechanochemical remediation mechanism of POPs contaminated soil.
机械化学降解（MCD）是一种很有前途的环保方法，可用于处理持久性有机污染物（POPs）。机械诱导自由基攻击被认为是引发和加速 POPs 脱氯和降解的关键因素之一。在这项研究中，使用实验分析和量子化学计算两种方法，探讨了机械化学过程中自由基的形成及其在六氯苯（HCB）污染土壤修复中的作用。研究发现，在研磨过程中可以生成氯代苯氧基自由基（CB-O），基于电子自旋共振（ESR）和 X 射线光电子能谱（XPS）的结果，它们在 HCB 的脱氯过程中起着至关重要的作用。还定位了沿着五氯苯氧基自由基（PeCB-O）形成的两个机械化学反应的过渡态，其能垒分别为 39.4 和 3.4 kJ/mol。还实施了局域轨道定位器（LOL）、Mayer 键序和拓扑分析，以详细描述该过程。通过福井函数分析还验证了 MCD 过程中自由基攻击主导的 HCB 脱氯途径。这项关于机械诱导自由基生成及其在 HCB 降解中相关作用模式的研究，将深入了解 POPs 污染土壤的机械化学修复机制。
