碳基分离膜耦合过硫酸氢盐活化对水中有机污染物的强化去除及其协同作用机制

The industrial wastewater contains various toxic and refractory organic pollutants, which are difficult to be removed by traditional water treatment technologies and pose potential threaten to ecological environment. Ultrafiltration and nanofiltration are effective advanced treatment technologies for wastewater. However, membranes could only separate pollutants via size-exclusion, which is unfavorable for removing the contaminants with sizes smaller than membrane pores and usually leads to the serious membrane fouling. Carbon-based catalysts are capable of activating PMS to produce the sulfate radical with strong oxidative ability, which is suitable for degrading and mineralizing refractory organic pollutants. This work designed and constructed carbon-based PMS catalytic layer on the surface and pore channels of ceramic membrane support, aiming to realize the integration of membrane filtration and PMS activation for water treatment. With the assistance of the catalytic oxidation, the removal of refractory organic pollutants, including the targets which are unavailable by size-exclusion, could be effectively enhanced. Furthermore, the surface and pore fouling of membrane could also be effectively inhibited under catalytic oxidation, resulting in improved membrane flux. The main content of this work focuses on the developing the carbon-based catalytic membrane, exploring the synergistic effect mechanism of catalytic membrane and investigating the membrane performance for advanced treatment of industrial wastewater. This work elucidates the synergistic mechanism between membrane filtration and PMS activation for pollutants removal, and provides a novel and effective strategy for advanced wastewater treatment.

工业废水中含有多种难降解毒性有机物，传统水处理工艺无法对其有效去除，对生态环境造成潜在危害。超滤及纳滤膜技术是一种有效的废水深度处理技术，然而膜单一的孔径筛分作用无法有效去除尺寸小于膜孔径的污染物，且存在严重的膜污染问题。碳基催化剂能高效活化过硫酸氢盐(PMS)生成强氧化性的硫酸根自由基，适用于难降解有机物的分解矿化。本研究拟在陶瓷膜表层与孔道内构建具有PMS催化功能的碳基催化层，实现膜分离技术与PMS活化技术的耦合。利用催化氧化作用辅助膜分离过程对水中难降解有机物高效氧化甚至矿化，增强对难以被膜截留的小分子有机物的去除能力。同时，催化氧化还能有效缓解膜表面及孔道污染，提高膜通量。本研究的主要工作包括碳基催化膜的开发、催化膜协同作用机理的探索以及催化膜对工业废水的深度处理性能考察。通过本研究，阐明膜分离-PMS活化耦合技术对污染物的协同去除机理，为废水深度处理提供一种新型有效的方式。

基于超滤或纳滤的膜分离技术在污水深度处理过程中，难以有效去除尺寸小于膜孔的难降解毒性有机物并存在严重膜污染问题。本项目针对这两个关键问题，在碳基分离膜上实现膜分离技术和过硫酸氢盐(PMS) 活化技术的耦合联用，以缓解传统膜分离过程的不足。围绕开发高效碳基PMS催化膜，设计并制备了氮掺杂纳米碳球、氮空位修饰的g-C3N4纳米管两种碳基PMS催化剂及氮掺杂碳包覆碳纳米管负载陶瓷膜(CNT@NC/Al2O3)、表面及孔道共修饰的氮掺杂碳包覆陶瓷膜(CM@NC)、碳纳米管插层的氮掺杂还原石墨烯氧化物二维膜(NRGO-OCNT)三种碳基PMS催化膜。对膜的形貌、结构、组成等进行了系统的表征。以水体中常见的毒性有机物为模型污染物，考察了催化膜的性能及主要影响因素的影响规律。探究了膜结构与性能之间的构效关系并揭示了膜分离与PMS活化的协同作用机制。结果表明，膜分离耦合PMS活化可以在超短的停留时间内(最小到0.36 s)实现对多种典型毒性小分子有机污染物如苯酚、4-氯酚、双酚A、磺胺甲恶唑等的完全去除。耦合工艺的性能明显高于单独膜分离过程及粉体多相催化过程。表面及孔道负载催化层的功能膜可以有效抑制膜表面及孔道污染。碳基催化膜可以在宽pH范围内及实际水背景下保持高效及良好的稳定性，展现出实际应用的潜力。催化膜优越的水处理性能主要归因于膜分离和PMS活化之间的协同作用：一方面，膜催化层活化PMS通过自由基过程(SO4•−及•OH)和非自由基过程(1O2和电子传递过程)共同作用于污染物的去除及膜污染抑制；另一方面，膜分离过程的外加压力及孔道修饰产生的纳米限域效应显著提高反应物传质速率，进而提高催化层的PMS活化效率。本项目的研究结果将为设计开发新型、高效碳基功能膜，推动膜分离耦合高级氧化技术在水处理中的实际应用提供重要的理论指导。