【作者】 王月；

【导师】 吴慧青；

【作者基本信息】 东华大学 ， 化学工程与技术， 2021， 硕士

【摘要】 近些年来,纳滤膜已被广泛用于饮用水净化、苦咸水淡化和废水回收/再利用等领域。商业化纳滤膜多为薄膜复合（TFC）结构,由致密的分离表层和多孔支撑层组成。其中分离表层由水相单体（如哌嗪）和油相单体（如均苯三甲酰氯）在油-水界面处聚合形成,对膜的分离性能起决定性作用;支撑层通常为超滤/微滤膜,主要起机械支撑作用。因此,界面聚合过程是决定分离表层的结构、形貌及复合膜性能的关键。本文主要通过引入中间层和利用大环分子Noria辅助的无支撑界面聚合来调控界面聚合过程以制备高性能的复合纳滤膜。本文共分为四章:第一章为绪论部分,首先对纳滤膜进行了简要概述,然后主要介绍了薄膜复合纳滤膜的改性研究进展,最后提出了本文的研究思路和主要工作。第二章将水溶性聚乙烯醇（wsPVA）纤维负载到聚砜超滤基底上作为牺牲模板中间层,制备复合纳滤膜。首先我们研究了不同wsPVA负载量对膜性能及膜表面形貌的影响。然后通过90℃热水溶解中间层wsPVA,进一步分析了牺牲中间层之后膜性能和表面形貌的变化。结果表明,wsPVA中间层与水相单体哌嗪（PIP）氢键相互作用,能有效地调控界面聚合;随着wsPVA负载量的增加,膜表面形貌从斑点状向条纹状最后向褶皱状转变,膜厚度降低,膜通量增加到63.1L/m²·h,盐截留保持在较高水平。在除去中间层之后,膜表面形貌未发生明显变化,但是断面结构中出现额外的纳米孔隙,通量进一步增加到83.5 L/m²·h。此外,该膜显示出典型的荷负电性,对不同染料（CR、MB、RB19、VB）都有优异的截留（>98%）,在长期操作过程中也保持了优异的稳定性。第三章借助一种大环分子Noria,利用Noria-PIP主客体化学作用及多酚化学作用,在油-水界面处获得无支撑纳米膜,随后转移到基底上形成复合纳滤膜。我们探究了Noria与PIP的主客体化学作用,系统地研究了不同Noria与PIP的比例、不同Noria+PIP总浓度、不同反应时间对纳滤膜性能的影响,重点关注了Noria对PA层与基底之间粘附性的影响。结果表明,无支撑的界面聚合可以在低单体浓度下进行,Noria与PIP之间的主客体化学作用及氢键相互作用能有效地调节此过程,同时Noria的多酚粘附性有助于界面聚合形成的无支撑聚酰胺（PA）纳米膜转移到不同基底上形成稳定的TFC膜。通过对PA层与基底分别优化,获得多种综合性能优异的复合膜。例如Noria-PA/PAN膜水通量高达43.0 L/m²·h·bar且Na₂SO₄截留为95.3%,Noria-PA/PP膜可同时用于极性及非极性溶剂体系的分离。此外,所制备的复合膜具有优异的抗污染性及长期运行稳定性。第四章是全文总结与展望。本论文针对纳滤膜现存的渗透性不高、渗透-选择之间的“trade-off”效应等问题,通过合理设计,有效地调控了界面聚合过程,获得了高性能的复合纳滤膜,为开发高性能的复合纳滤膜提供了有价值的新思路。更多还原

【Abstract】 In recent years,nanofiltration membranes have been widely used in drinking water purification,brackish water desalination,and wastewater recovery/reuse.Commercial nanofiltration membranes are mostly thin film composite（TFC）structures,consisting of a selective layer and a porous support layer.The selective layer is formed on the interface of oil-water,wherein water phase monomers（such as piperazine）polymerized with organic phase monomers（such as trimesoyl chloride）,and it primarily determines the separation performance of the membrane;the substrate is usually ultrafiltration/microfiltration membrane,which mainly plays the role of mechanical support.Therefore,the interfacial polymerization process is the key to determining the structure,morphology and performance of the composite membrane.In this thesis,the introduction of an interlayer and the employment of macrocyclic Noria-assisted support-free interfacial polymerization were designed to control the interfacial polymerization process for the purpose of achieving high-performance nanofiltration membranes.This thesis is divided into four chapters:The first chapter is the introduction.First,it briefly introduces nanofiltration membrane,then mainly summarizes the research progress of nanofiltration membrane,and finally puts forward the research ideas and main work of this thesis.In the second chapter,water-soluble PVA（wsPVA）fibers were firstly loaded on a polysulfone ultrafiltration substrate as the sacrificial template interlayer,and a TFC nanofiltration membrane was prepared.The effect of wsPVA loadings on the membrane properties and morphologies were studied.Furthermore,the wsPVA was dissolved in 90℃water,and the properties and morphologies of membrane were also investigated after removing the interlayer.The hydrogen bonding between wsPVA and PIP could effectively regulate the interfacial polymerization;the results show that increasing of wsPVA loading,membrane surface changes from spotty to stripe and finally to crumples and membrane thickness decreases,the membrane flux increases to 63.1 L/m²·h,and salt rejection remains at a high level.After removing the interlayer,the membrane surface morphology does not change significantly,but additional nanovoids appear in membrane structure,the water flux further increases to 83.5 L/m²·h.The membrane shows negative charged and has excellent rejection of different dyes（CR,MB,RB19,VB）（>98%）,and also maintains excellent stability during long-term operation.In the third chapter,Noria,a macrocyclic molecule,was used to assist support-free interfacial polymerization via Noria-PIP host-guest chemistry and polyphenol chemistry to prepare freestanding nanofilms,then those nanofilms were transferred to various substrates construct TFC nanofiltration membranes.The host-guest chemistry of Noria and PIP was firstly determined,the effects of C_Noria/C_PIP,the total concentration of Noria+PIP and the reaction time on the performance of nanofiltration membranes was subsequently studied.Focused on the impact of Noria on the adhesion between PA layer and substrate.Support-free interfacial polymerization could occur at a low monomer concentration,and the host-guest chemistry and hydrogen bond interaction between Noria and PIP can effectively regulate this process.At the same time,Noria intrinsic polyphenol adhesion contributes to the formation of a stable TFC nanofiltration membrane.By optimizing the PA layer and the substrate respectively,varieties of TFC membranes with excellent comprehensive performance can be obtained.For example,the water flux of Noria-PA/PAN membrane is as high as 43.0 L/m²·h·bar and the rejection of Na₂SO₄is 95.3%.Noria-PA/PP membrane can be used for the permeation of polar and non-polar solvent.In addition,the prepared TFC membrane has excellent pollution resistance and stability.The fourth chapter is the summary and outlook of the thesis.We focus on the principal problems of state-of-art nanofiltration membranes such as low permeability,“trade-off”effect between permeability and selectivity.Through rational design,the interfacial polymerization process is effectively controlled and advanced nanofiltration membrane is finally obtained.This work sheds light on the development of high-performance composite nanofiltration membranes.更多还原