水分子有序透过且亲水性高的分离膜开发及高品质饮用水处理效能与机制

Conventional ultrafiltration membranes have good performance for the removal of turbidity and contaminants in relatively large size such as microorganisms, while most of the organic compounds cannot be removed. Plus low flux and membrane fouling, the application of conventional ultrafiltration membrane is confined. We intend to develop a novel hybrid filtration membrane based on PVDF membranes in this work by inducing super hydrophilic nano mica materials of high chemical stability with restrained nanochannels between layered mica nanosheets for water permeation. Together with the regulation of the membrane pore size, novel high-flux membranes with small molecular weight cut-off, appropriate permeation of essential trace elements and good antifouling performance are supposed to be developed. Collaborative water treatment processes for drinking water of high quality are also to be designed. Surface remote plasma modification on mica particles and enlarging of the nanochannels are to be carried out; Novel high performance membranes are to be developed based on mixing modified nano mica materials with PVDF membranes and the regulation of the pore size; The quality of the yielding water and the mechanism are to be assessed; The mechanism of ordered transport of water molecules through the restrained nanochannels between the mica nanosheets and the coordination of it with the super hydrophilicity of mica which raises the flux are to be illustrated. Influence of microstructure of the developed membranes on the permeation of trace elements and the rejection of small-size organic chemicals are to be observed. The rejection of a variation of contaminants, the permeation performance of essential trace elements and the interaction between the membrane and the solutes are to be interpreted. The mechanism of fouling of our novel membranes are also to be investigated.

现有超滤膜存在只能去除饮用水中浊度、微生物等大尺度污染物，大部分有机物不能去除，通量低（投资大）、易污染等问题，限制了其应用。本课题拟将具有超亲水界面、层间纳米受限通道、高化学稳定性的纳米云母与PVDF杂化，并对PVDF膜孔径进行调控，制备水分子可在云母的层间纳米受限通道中高速传输、化学稳定性好、截留分子量小、微量元素透过、抗污染的新型分离膜，并构建以该膜为核心的高品质饮用水处理工艺。开展云母层间纳米通道扩增及其表面低温等离子体改性；基于纳米云母与PVDF杂化以及PVDF膜孔径调控，开发新型高性能膜；评价以该膜为核心的高品质饮用水处理工艺的水处理效能与机理；解析水分子在云母层间纳米受限通道高速有序传输的原理及其与云母超亲水性协同增大膜通量的机制；考察膜微孔结构及尺度等对微量元素透过、小分子有机物截留的原理；阐明新型分离膜对污染物截留和对微量元素透过的效能、相互作用规律及膜污染机制等科学问题

饮用水水源中的各种有机污染物是饮用水安全的主要威胁，对此，很多自来水厂采用臭氧-活性炭工艺对其进行处理，但该工艺对有机物的去除率并不高，而且还会产生溴酸盐等副产物。近年来，自来水厂开始尝试将纳滤膜用于处理饮用水中的有机污染物，纳滤膜虽然可以大大提高有机物的去除率，但是，其产水率较低，能耗和投资较大，并且其在去除有机物的同时也去除了水中部分矿物质，使饮用水的品质降低。超滤膜的突出优点是能保留水中的矿物质，对浊度、微生物等大尺度的污染物去除效果好，但，其存在对小分子有机物去除率低，膜通量相对较小，易污染等问题。对此，本课题将具有超亲水界面、受限纳米通道、高化学稳定性的纳米云母与PVDF进行共混杂化、并通过PVP调控膜孔径，制备出了新型超滤膜；该超滤膜过滤水时，水分子可以在超滤膜中云母的层间受限纳米通道中高速传输、小分子有机物能有效去除，但，微量元素可以透过，并且抗污染性能好；以此提出将该新型纳滤膜用于饮用水深度处理，构建以该超滤膜为核心的高品质饮用水处理工艺系统，并解析水分子在云母层间受限纳米通道高速有序传输的原理及其与云母协同增大膜通量的机制，阐明超滤膜微孔结构截留小分子有机物、透过微量元素的原理。研究结果表明：纳米复合颗粒与PVDF共混的杂化膜较未杂化的PVDF超滤膜，通量提高了97.4%，接触角下降20.8%，膜孔隙度提高34.5%，拉伸强度提高33.5%；该超滤膜对模拟水、实际地表水的处理效果好、稳定，对水中浊度、TOC和UV254去除率分别大于98%、84%和83%，均高于未进行杂化的PVDF超滤膜；同时杂化膜的抗污染性能好，清洗周期延长70%，水力清洗时通量恢复率高出未杂化膜8.23%-10.41%，处理实际地表水时化学清洗通量恢复率为98.84%；杂化膜中的纳米颗粒在酸液和碱液中长期浸泡时的流失率很低，说明纳米颗粒和PVDF超滤膜相容性好、稳定。这些研究成果，为饮用水深度处理开辟了新的途径，特别是为高品质饮用水处理提供了科学与技术支持，对发展水的膜分离理论，推动膜技术在水处理中的推广应用都具有重要意义。