超分子修饰纳米铁膜对水环境中亚硝基胺的降解及界面转化机理研究

N-nitrosodimethylamine (NDMA) in natural water was strong carcinogenic compound which was difficult to be degraded by the current alternative treatment methods. There is considerable need for the high-efficiency method to remove the pollutant. In this research, super-molecule cyclodextrin modified nano iron was self-assembled in the surface of polymer membrane. This modified nano iron membrane could efficiently selective capture and degrade NDMA due to its special surface structure and chemical property. The structure of nano iron and assembled layer should be characterized in the study. The relevance between the physicochemical property of nano iron and its efficiency for NDMA reduction should be studied in this research .To elucidate the adsorption and reduction mechanism of NDMA by modified nano iron membrane, the microcosmic structure of nano iron and the transformation processing of NDMA in the material surface could be researched. The influence of coexisting mater in natural water and environmental factor on NDMA removing by nano iron will also be investigated. This research should provide a new approach to resolve the NDMA pollution and develop the method and theory on account of nano iron reduction. Therefore, this research has important significance both theoretical and practical in water deep purification and the water quality enhancing.

存在于环境水体中的亚硝基二甲胺（NDMA）污染物具有强致癌性，其在水体中浓度低、难降解，难以采用传统水处理技术进行处理，迫切需要建立新型的高效去除方法及原理。本项目设计合成具有选择性识别、还原降解NDMA功能的环糊精超分子修饰纳米铁自组装膜，表征膜层中纳米铁的微观结构及化学性能；研究修饰型纳米铁的结构性能与降解转化NDMA效能的关系，获得优化纳米铁性能的结构调控机制；研究NDMA污染物在纳米铁膜表界面的还原转化途径，揭示污染物在固/液界面吸附-还原反应的本质和机理；探明复杂水体环境条件对修饰型纳米铁膜降解污染物的影响机制。该研究为解决水环境中亚硝基胺类强致癌物的污染问题开辟了一条新的途径，发展了纳米铁还原降解NDMA的基本原理和方法，在水质深度净化及提高水质安全方面具有重要的应用价值。

本项目对Fe0-PAA-MAH-β-CD/PEI膜以及Fe0-PDADMAC/PAA膜的进行了制备及形貌表征，同时获得了痕量NDMA在Fe0-PAA-MAH-β-CD/PEI膜界面降解转化的效能，获得了Fe0-PAA-MAH-β-CD/PEI膜结构对NDMA降解转化的影响规律；通过考察β-CD及β-CD组装膜对NDMA吸附性能，获得Fe0膜吸附-还原NDMA污染物的转化过程和机理；探明复杂水体环境条件下，常见几种共存离子和天然有机物对Fe0膜降解NDMA污染物的影响作用规律。合成获得了新的阳离子聚电解质PAA-MAH-β-CD与Fe离子进行配位，并与阴离子聚电解质PEI交替组装于荷电化的PAN平板膜。通过控制PAN平板膜的荷电化程度以及组装层数、组装后处理方式可以调控复合膜的通量及Fe0量。Fe离子通过配位的方式与聚电解质结合，最终形成的Fe0颗粒在膜表面分布均匀，且尺寸在200nm左右。NDMA在Fe0界面还原的过程中，阳离子聚电解质所含的β-CD对NDMA具有一定的吸附效应，但对于溶液中强极性的痕量NDMA，这种吸附作用贡献不大，NDMA的转化主要依靠膜界面Fe0的还原作用。还原的产物检测到NH4+，另外一种转化产物推测为二甲胺。Fe0还原NDMA后形成的Fe2+/3+可以与膜表面的羧基络合而稳定在膜表面。由于复合膜含有的羧基基团的缓冲作用，Fe0膜还原NDMA过程中，溶液pH值在中性范围时反应活性较高。而溶解氧对于Fe0膜还原NDMA的影响也不大。溶液中存在的HCO3-、Cl-、SO42-对Fe膜还原NMDA没有抑制效应，而NO3-仍然会与NDMA竞争Fe0释放的电子。本研究中还制备了Fe0-PDADMAC/PAA膜，Fe离子与阴离子聚电解质配位，也保证Fe0颗粒在膜表面均匀稳定的分布，对NDMA的还原转化速率更高，且膜中含有的配位基团对于反应中对生成的Fe离子也具有较好的稳定作用。