基于惰性与催化电极的多溴联苯醚(PBDEs)电化学还原降解及脱溴机理研究

Polybrominated diphenyl ethers (PBDEs), along with their widely used in human activities, are among one of the most frequently detected international persistent organic pollutants in environment, which have severe impact and even carcinogenicity on human health. The current pollution situations by PBDEs in China are extremely serious. Electrochemical reductive dehalogenation is among one of the most promising remediation methods toward halogenated organic compounds, but despite electrochemical debrominantion of PBDEs has been carried out preliminarily from worldwide, few studies on the systematic electrochemical dehalogenation of PBDEs to explain the reduction processes have been conducted: the electron transfer mechanism and thermodynamic studies on PBDEs are still lost; the effects of molecular structure on reductive debrominatin reaction have not been comprehensively demonstrated; the electrochemical debromination mechanisms toward PBDEs are still not very clear. Therefore, we wish to address the above mentioned mechanistic aspects of reductive debromination of PBDEs in this research. Cyclic voltammetry, potentiostatic electrolysis, gas chromatography-mass spectrometry and scanning probe techniques as well as other tools are used in this research. The electron transfer mechanism of electrochemical dehalogenation of PBDEs will be firstly investigated, based on which further develop the thermodynamic models of dehalogenation processes of PBDEs. Furthermore, the inherent relationships between the molecular structure of PBDEs and the dehalogenation reactivity, together with the influences of solvent conditions and cathode materials on the dehalogenation processes will be investigated, so as to better understand the principles and mechanisms of electrochemical debromination of PBDEs. We hope it can not only complete the electrochemcial dehalogenation mechanisms toward PBDEs through this work, but also it could further provide scientific support for the potential application of electrochemical reduciton method to remove PBDEs from polluted water.

多溴联苯醚（PBDEs）是一类在人类生产生活中大量使用、对人类具有潜在危害甚至致癌性、在水等环境介质中极易监测到的全球性持久性有机污染物。我国当前受PBDEs污染的形势尤为严峻。尽管国际上对PBDEs的电还原脱溴机理和方法进行了初步探讨，但当前还缺少系统的电还原脱溴研究：PBDEs的电子转移机理、热动力学研究仍然缺失；其分子结构对脱溴反应的影响还没得到全面阐述；电还原脱溴机理尚不清楚等。因此，本项目拟围绕上述问题开展研究，采用循环伏安、恒电位电解、气-质联用以及扫描探针等手段和技术，以期揭示PBDEs还原脱溴过程的电子转移机理；构建电还原脱溴反应的热动力学模型；阐明分子结构特性与脱溴活性的内在关联；考察溶剂条件、电极特性对脱溴反应的影响；明确PBDEs电还原脱溴过程的原理与机制。本研究不仅可以完善对PBDEs电还原脱溴机理的认识，还有望为电还原技术应用于含PBDEs污水的处理提供理论支撑。

有机卤化物主要包括有机氯化物和有机溴化物，是环境中最常见、毒性最高、受关注度最多的一类持久性有机污染物，广泛存在于各类环境介质中。有机卤化物的毒性主要来自于卤原子，因此，该类物质的脱毒处理在某种程度上转变成了脱卤过程。电还原脱卤技术被认为是一种极具应用前景的污染控制技术，可以实现对环境中有机卤化物的高效还原脱卤降解，无需投加化学药剂，近年在污染控制及电子转移机理方面引起了国际社会的广泛关注和研究。本项目以有机卤化物的电化学还原脱卤过程为研究对象，系统考察了有机卤化物的电子转移机理，探讨了电还原脱卤过程的热动力学特性，研究了催化电极（Ag）的电催化脱卤活性及机理，分析了分子电化学与电催化的内在关联，以期全面揭示有机卤化物的电还原脱卤原理与机制。研究取得的重要原创性学术成果包括：构建了有机卤化物的分子结构特性与脱卤活性和脱卤机理的内在关联，首次建立了基于分子结构的量子化学参数与有机卤化物氧化还原电位间的线性自由能关系；揭示了有机卤化物分子结构与电子转移机理的联系，提出了电子转移系数可以作为鉴别顺序电子转移机理和同步离解电子转移机理的判别标准，并指出分子结构决定电子转移机理；原创性的提出了催化电子转移理论，揭示了电催化脱卤反应的本质，建立了分子电化学与电催化的内在联系；提出了电子转移过程的热动力学模型，成功预测了脱卤反应标准自由能与活化自由能间的关系；通过同时控制电子转移和质子转移过程，阐明了电化学还原脱卤机理。本项目不仅完善了国际上对电化学还原脱卤机理的认识，还为环境中有机卤化物的电还原脱卤技术提供了理论技术支撑。