传质过程强化对二氧化铅电催化性能的影响研究

The hydroxyl radicals generated on the PbO2 electrode surface are adsorbed hydroxyl radicals. Due to the limitation of mass transfer, it is difficult for the absorbed hydroxyl radicals to interact with the organic molecules fully.This results in a low apparent catalytic performance of the PbO2 electrode. In this project, we proposed to introduce the adsorption process into the electro-catalytic process of lead dioxide electrode, which can form an in-situ integration of adsorption and electro-catalytic process. Due to the to-and-fro movement of adsorption particles, the migration of organic molecules to the electrode surface can be enhanced, which will increase the contact probability of organic molecules and hydroxyl radicals. Thereby, the apparent catalytic performance of the electrode can be improved. To do this, we plan to form the in-situ system based on the hollow titanium-base lead dioxide electrode and Fe3O4/PPy/TiO2 particles. And the in-situ system will be used to treat organic wastewater. The first key point of this project is to reveal the synergistic effect between adsorption and electro-catalytic processes on the organic wastewater degradation. The second one is to reveal the reaction pathway of typical organic molecules in the in-situ system. The results of the project can provide theoretical and technical supports for the future application of PbO2 electrode in electrochemical wastewater treatment.

二氧化铅电极生成的羟基自由基以吸附态为主；由于传质过程的限制，有机物分子难以与吸附态羟基自由基充分接触，造成该电极的表观催化性能较低。本项目提出将吸附过程引入二氧化铅的电催化过程，组成原位吸附-电催化降解体系，利用吸附剂颗粒在溶液本体与电极表面之间的往复迁移过程，完成有机物分子从溶液本体向电极表面处的强制传质过程，提高其与吸附态羟基自由基的接触机率，进而提高有机物的降解效率。为此，以空心钛基体二氧化铅电极（其空心处放置可变电磁场系统）和带Fe3O4磁性内核的PPy/TiO2吸附剂颗粒为核心，构建原位吸附-电催化体系，并利用该体系进行有机物的催化降解。本项目重点研究原位吸附-电催化体系中，吸附过程与电催化过程对有机物的协同降解机理与机制，并分析典型有机物分子在该体系中的迁移转化过程以及降解途径。本项目的研究结果将为二氧化铅电极在电催化氧化技术中的进一步应用提供相应的理论及技术支持。

由于传质过程限制，有机物分子难以与PbO2电极表面吸附态羟基自由基充分接触，造成该电极的表观催化性能较低。本项目提出将吸附过程引入PbO2电催化过程，组成吸附-电催化降解体系，利用吸附过程完成有机物分子从溶液本体向电极表面处的强制传质过程，提高其与吸附态羟基自由基的接触机率，进而提高有机物的降解效率。项目发现采用PVDF掺杂改性，可以显著改善PbO2电极形貌，提高电极安全性能、催化性能及稳定性。综合考虑，确定PbO2电极沉积液中合适的PVDF添加量为2g/L。项目后续工作都以该种类型电极作为阳极。在此基础上，以包有磁性内核的Sb-SnO2颗粒吸附于钛电极外层，构成新型2.5D电极体系。新2.5D体系提高了电极系统的稳定性，增加体系的羟基自由基产量，显著增加体系的传质系数，使得在同等条件下，2.5D体系对酸性红G电催化降解的处理效率提高、处理能耗下降。再以Fe3O4为核心，合成具有吸附能力的复合磁性吸附剂，将其引入电催化过程，构建异位吸附-电催化体系，并完成对低浓度有机物的电催化降解过程。同等条件下，联用技术对酸性红G废水处理能耗为0.474kWh/gCOD，远小于单纯电催化技术时的1.24 kWh/gCOD，能耗降低61%。本项目相应的研究为二氧化铅电极在电催化氧化技术中的进一步应用提供相应的理论及技术支持。