多孔碳电极增强电化学/臭氧耦合体系去除水中PPCPs机理研究

Pharmaceutical and personal care products (PPCPs) are a diverse group of environmental chemicals that are difficult to be biodegraded and removed by conventional water treatment processes. Besides, they have potential risk for the endocrine and reproduction system of human body even with very low concentration. This research project is trying to probe a new approach for removing trace level of PPCPs from aqueous solution by porous carbon electrode for enhancing the coupling processes of electrochemical oxidation and ozonation. A series of porous carbon materials, including reticulated vitreous carbon (RVC), activated carbon/Polytetrafluoroethene (PTFE), active carbon fiber (ACF), and carbon nanotube (CNTs)/PTFE et al., are proposed as cathodes for increasing the efficiency of the coupling processes of electrochemical oxidation and ozonation. Then, the mechanism responsible for the results is also proposed to be investigated with various experimental methods. The relationship between the chemical and physical properties of porous carbon materials and the efficiency of the coupling processes of electrochemical oxidation and ozonation is proposed to be revealed. Moreover, the removal kinetic model, influence factors, reaction pathways, production of bromate, and the change of toxicity and biodegradability of three typical PPCPs by the combined process is planned to be studied. The outcome of the project will be beneficial for understanding the mechanisms of PPCPs removal by the coupling processes of electrochemical oxidation and ozonation. And this study has important theoretical value and practical significance for developing new water treatment technologies.

医药品与个人护理品（PPCPs）是一类广泛存在、能引起人体不良健康反应的有机污染物，难以生物降解和通过常规水处理工艺去除，即使微量也可能引起人类内分泌及生殖系统紊乱。此项研究基于水处理过程中单独电化学与单独臭氧氧化的局限性，探索多孔碳电极增强电化学与臭氧耦合体系去除水中低浓度PPCPs的新途径。尝试将网状玻璃态碳、活性碳/聚四氟乙烯、活性碳纤维、碳纳米管/聚四氟乙烯等多种多孔碳电极用于增强电化学/臭氧耦合体系的效能；采用循环伏安法等多种试验方法探索多孔碳电极增强电化学/臭氧耦合体系效能的作用机制和多孔碳材料物理化学性质与其增强体系效能的关系；并对该体系去除和降解水中典型PPCPs的效果、影响因素、反应途径及溴酸盐生成、急性毒性和可生化性的影响等进行研究，建立去除动力学模型。此项目的工作有助于加深对电化学/臭氧体系去除水中PPCPs机理的理解，对开发水处理新技术、积累知识储备具有重要意义。

单独臭氧氧化难以彻底快速地降解水中难降解有机污染物，且臭氧的利用效率较低。当将活性炭与臭氧结合使用时，有机污染物的降解效率得到了大幅提高。这是因为活性炭表面的碱性活性官能团能够促进臭氧分解并转变为羟基自由基的效率。但是，随着活性炭在臭氧环境中反应时间的延长，活性炭表面碱性官能团不断减少，活性炭对臭氧分解的促进能力快速下降。该研究通过在活性炭纤维表面施加阴极电场，维持了活性炭纤维表面的结构性质及官能团数量，不但避免了臭氧对活性炭纤维表面结构及官能团的破坏，保持了活性炭纤维对臭氧的催化活性，还通过在电化学还原氧气产生过氧化氢与臭氧反应生成更多的羟基自由基，大大提高了臭氧的利用效率和污染物的降解及矿化速率，为微量难降解有机物在水环境中的高效低耗降解去除提供了一种新的理论解决方案。.通过研究比较不同工况下活性炭纤维耦合臭氧和电场作用条件下活性炭纤维耦合臭氧对难降解有机物硝基苯的降解和矿化，通过对反复使用100次前后活性炭纤维的表征和分析，发现其对硝基苯的降解符合拟一级动力学，其动力学常数仅从14.90╳10-2.min-1缓慢下降到12.18╳10-2.min-1，且反复使用前后活性炭纤维的比表面积、官能团和结构保持稳定；而在不通电的同等情况下，活性炭纤维耦合臭氧的反应同样符合拟一级动力学，其动力学常数从8.47╳10-2.min-1快速下降到2.25╳10-2.min-1，且反复使用前后活性炭纤维的表面官能团和结构发生明显变化。该研究创新性地提出自由电子在阴极注入可以将活性炭纤维从臭氧的促进剂转变为催化剂理论，合理地解释了相关实验现象。研究成果在2016年以Short communication的形式发表在顶级期刊“Chem. Eng. J.”(IF 5.310)上, 该研究发现了一种新的能够高效快速并可持续使用地降解和矿化水中难降解有机污染物的新方法，目前后续研究正在进行中。