Department of Solid Waste Treatment and Recycling, 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.
BCEG Environmental Remediation Co. Ltd.,No.6 Jingshun East Street, Chaoyang District, Beijing 100015, China.
J Hazard Mater. 2017 Jul 5;333:116-127. doi: 10.1016/j.jhazmat.2017.03.022. Epub 2017 Mar 12.
Recent researches indicate that mechanochemical treatment (MCT) is a promising method to degrade the environmental hazards, especially in the area of persistent organic pollutants (POPs) disposal. However, the mechanochemical dechlorination mechanism of POPs still needs to be further verified. In this mechanochemical process, hexachlorobenzene (HCB) was chosen as a model pollutant with aluminum and alumina (Al+AlO) powders as the co-milling regents. Both of the intermediate analysis and quantum chemical calculations were adopted to elucidate the free radical dechlorination mechanism of HCB. The solid residues were characterized by electron spin-resonance (ESR) spectroscopy, Fourier transform infrared (FTIR) spectra and X-ray photoelectron (XPS) spectra, which proposed that the radicals formed in the mechanochemical process were chlorinated phenoxyl radicals (CB-O). Four quantum chemical descriptors were selected in predicting the intermediates and reaction pathway: (i) atomic charge, (ii) electrostatic potential (ESP), (iii) frontier molecular orbitals (FMO) theory and (iv) dual descriptor. Then, a stepwise dechlorination mechanism based on CB-O was proposed. It was found that the intermediates and radical-related reactions in the mechanochemical dechlorination of HCB are quite different from that happen in a typical photocatalytic dechlorination process. Impacts of different radical reactions on the dechlorination of HCB were also compared at last.
最近的研究表明，机械化学处理（MCT）是一种很有前途的方法，可以降解环境危害，特别是在持久性有机污染物（POPs）处理领域。然而，POPs 的机械化学脱氯机制仍需要进一步验证。在这个机械化学过程中，六氯苯（HCB）被选为模型污染物，铝和氧化铝（Al+AlO）粉末作为共磨试剂。采用中间分析和量子化学计算来阐明 HCB 的自由基脱氯机制。通过电子自旋共振（ESR）光谱、傅里叶变换红外（FTIR）光谱和 X 射线光电子能谱（XPS）对固体残留物进行了表征，提出了在机械化学过程中形成的自由基是氯化苯氧自由基（CB-O）。选择了四个量子化学描述符来预测中间体和反应途径：（i）原子电荷，（ii）静电势（ESP），（iii）前沿分子轨道（FMO）理论和（iv）双描述符。然后，提出了基于 CB-O 的逐步脱氯机制。研究发现，HCB 的机械化学脱氯过程中的中间体和与自由基有关的反应与典型的光催化脱氯过程中的反应有很大的不同。最后还比较了不同自由基反应对 HCB 脱氯的影响。
