三相多孔空气阴极的制备及其电催化降解多溴联苯醚的机制研究

As a new kind of persistent organic pollutants (POPs), there is no solution to the problems such as time consuming, low efficiency, and secondary pollution during the degradation of polybrominated diphenyl ether ( PBDEs ). Based on the dual effect of good cathodic reduction and anodic oxidation of electrochemical degradation techniques, an efficient, inexpensive, and environment-friendly electrocatalytic process for the degradation of PBDEs will be developed in this research. In order to improve the efficiency of the dehalogenation of cathodic catalytic reduction and reduce energy consumption of oxygen supply, efficient and stable three-phase porous cathodes are prepared by improving existing materials and preparation methods of cathodes and combining the analysis of morphology characterization and electrocatalytic activity of electrodes. By using air as the oxygen source, an electrochemical system will be made up of the cathodes prepared and good anodes selected. Based on the efficient dehalogenation in preliminary experiments, the degradation of PBDEs will be studied. The laws of the degradation and priority control of PBDEs with different substrates and molecular structure will be revealed by investigating the mechanism of PBDEs with different solvents, the substituent position and number of bromides. At the same time, reaction kinetics, degradation pathways and product toxicity of PBDEs will be further analyzed. Ultimately, the research will provide theoretical guidance and scientific basis for the degradation of PBDEs as well as the application of electrochemical techniques.

作为一种新型的持久性有机污染物，多溴联苯醚（PBDEs）的降解存在时间长、效率低、二次污染等问题，目前尚未有有效的解决方法。本研究基于电化学降解方法特有良好的阴极还原和阴阳极氧化的双重功效，拟开发一种高效经济、环境友好的PBDEs电催化技术。为提高现有阴极催化还原脱卤效率、降低氧源供给能耗，研究改进现有阴极材料和制备工艺，并结合电极形貌表征和电催化活性分析制备出高效稳定的三相多孔阴极；以空气作为氧源，与筛选的优良阳极构成电化学体系，在前期实验保证了高效脱卤的基础上，研究其对PBDEs的降解机制；并考察不同溶剂、溴代位置、溴代数目PBDEs的降解机制，揭示不同底质条件、不同分子结构PBDEs的降解难易和优先控制规律；同时进一步进行反应动力学、降解路径及产物毒性分析，最终为PBDEs的降解以及电化学技术的应用提供理论指导和科学依据。

作为一种新型的持久性有机污染物，目前多溴联苯醚（PBDEs）的降解尚未有有效的解决方法。项目基于电化学体系对难降解有机物还原脱卤的优势，改进现有阴极材料和制备工艺，制备出高效稳定的三相多孔空气电极。与筛选的优良阳极组合，以空气代替纯氧，构建新型电化学体系。以含有苯环和卤取代基的有机物为代表进行降解实验研究，在电极间距3cm，电流密度80mA/cm2，电解质浓度0.2mol/L，固定pH值4，通气量60mL/min，浓度50mg/L的初始底物，1h即可完全降解（降解率达100%），卤取代基几乎完全脱除，过氧化氢的累积浓度可达到900mg/L，2h矿化率达到80%；经过多次重复使用后，电极表面形貌基本上不发生变化。机理研究表明，所构建的电化学体系主要通过阴极实现催化脱卤反应实现卤原子的脱除，而阴阳极的氧化作用又可以直接将中间产物再次降解，实现了阴阳两极催化脱卤的双效联合。同时，构建了催化还原降解PBDEs的反应体系，可实现1h内降解率达到87%以上。考察了系统对PBDEs的降解过程和动力学，表明体系中多溴联苯醚首先转化为九溴联苯醚和八溴联苯醚，随后再逐步转化为低数目的溴联苯醚，而低数目的溴联苯醚相对较为稳定而更难被降解，从而为不同分子结构PBDEs的降解难易提供参考。同时，电化学体系可实现过氧化氢和过硫酸铵的高原位产出，同步反应可取得更好的电流效率。研究最终可为PBDEs的降解以及电化学技术的应用提供理论指导和科学依据。