聚酰胺复合膜微孔支撑基底的研究进展

通过界面聚合法获得的聚酰胺复合膜在污废水处理、海水淡化等领域得到广泛应用,然而聚酰胺复合膜的结构对其应用起到关键作用,以往研究多数聚焦在分离层,而对复合膜微孔支撑基底的研究相对较少。研究表明,微孔基底的物化特征对于聚酰胺分离层结构的形成及复合膜性能起着至关重要的影响作用。为此,本文从支撑基底的制备工艺出发,围绕微孔基底的不同改性手段,介绍了传统基底改进方法和新型基底的材料与结构,并探讨了基底结构对压力驱动膜（纳滤、反渗透）与渗透压驱动膜（正渗透）分离层结构与性能的影响。分析表明,具有高孔隙率、亲水性好的微孔基底可有效调控界面聚合过程中单体的储存与扩散,有利于获得高渗透和高选择性能的聚酰胺复合膜。因此,未来仍需从聚合物材料及纳米改性等几个方面,发展更具潜力的微孔基底材料与结构,以推动聚酰胺复合膜的应用发展。     

聚酯酰胺反渗透复合膜的制备及其表征

以间苯二胺、氨基葡萄糖与均苯三甲酰氟为反应物，在聚砜基膜上用界面聚合法制备聚酯酰胺反渗透复合膜。用红外光谱仪（FT-IR）和扫描电子显微镜（SEM）及原子力显微镜（AFM）对所制备膜的结构和形态进行表征。红外光谱的结果表明有聚酰胺和聚酯结构的生成，扫描电镜结果显示复合膜表面呈明显的峰谷状结构，原子力显微镜分析结果表明聚酯酰胺膜表面粗糙度较聚酰胺膜表面粗糙度大。实验考察了界面聚合反应中的水相单体配比对所制备复合膜分离性能的影响；并进一步考察了操作条件及物料性质对制备的聚酯酰胺反渗透复合膜分离性能的影响。研究表明：随水相中氨基葡萄糖配比的增加，复合膜的脱盐率下降，通量上升。聚酯酰胺反渗透复合膜在1．6MPa操作压力下水通量达到27．4L／m^2·h以上，对2000mg／L的NaCl、KCl、MgCl2、Na2SO4、MgSO4等无机盐的脱盐率均在97．5％以上。     

金属有机骨架/聚酰胺薄层纳米复合膜的研究进展

相较于传统聚酰胺薄层复合（TFC）膜,金属有机骨架/聚酰胺薄层纳米复合（TFN）膜得益于MOFs材料的高比表面积、有序可控的孔隙结构、良好的聚合物相容性和可定制的化学功能,展现出更高的渗透选择性,在工业应用中显示出巨大的分子和离子分离潜力。本文首先简述了MOFs聚酰胺复合膜的研究背景,然后从MOFs材料的特性和MOFs聚酰胺复合膜的制备策略两个方面出发,总结了MOFs聚酰胺膜研究的最新进展。讨论了MOFs的物化特征在TFN膜的微观结构和分离性能中起的作用;介绍了MOFs聚酰胺复合膜的制备策略,重点对MOFs负载方法及效率进行了分析。最后简述了MOFs聚酰胺复合膜在气、液体系分离中的应用;对MOFs聚酰胺膜在应用过程中的稳定性问题进行了分析,并对未来MOFs聚酰胺复合膜优化MOFs负载和功能性设计的研究进行了展望。     

功能性中间层对聚酰胺膜水处理性能影响

含聚酰胺层（PA）的复合膜自被发明以来，就广泛应用于纳滤（NF）、反渗透（RO）、正渗透（FO）等水处理领域。但是，聚酰胺膜的渗透性和选择性的相互制约使得对其的研究亟待产生新的突破。近年来，一种位于基膜和选择层之间的中间层成为膜制备研究的热点。这种中间层会影响聚酰胺层的形貌以及界面聚合过程，因而较先前的聚酰胺膜及纳米材料复合膜在通量及截留率方面均有一定提高，是解决目前聚酰胺膜渗透性和选择性矛盾的重要途径。综述了近年来有关中间层对聚酰胺膜水处理性能的影响和机理，介绍了基于有机涂层、纳米材料及二者结合的不同类型中间层的结构和性能，以及以此制备的聚酰胺膜的性能变化，为制备高性能的聚酰胺膜提供依据。     

反渗透复合膜研究(Ⅱ)初生态膜的原位改性

界面聚合是制备超薄复合膜是通过两种互不相溶的单体溶液在多孔支撑的表面进行聚合,再经热处理,洗涤等工艺后得到超薄复合膜。初生态膜(IniM)是指完成界面聚合反应而未经后处理（热处理,洗涤等）的膜。采用间苯二胺和均苯三甲酰氯通过在多孔聚砜膜上界面聚合得到初生态反渗透复合膜,再用四乙烯五胺对初生态膜进行表面原位改性,经后处理得到改性反渗透复合膜。对改性反渗透复合膜面XPS分析结果为：改性膜表面的O/N比明显低于未改性的,这说明四乙烯五胺通过反应接枝在膜表面;同时,改性膜面接触角大于未改性膜的,进一步证明了这一点。脱盐性能测试结果为：改性反渗透复合膜的水通量和NaCl脱除率随着进水pH值的增大而减小,这与未改性的反渗透复合膜变化趋势完全相反;这是因为改性反渗透复合膜面含有氨基（—NH₂）或亚胺基（=NH）,当pH值增大时,其与水的亲和力减小;而未改性的反渗透复合膜表面含有羧基（—COOH）, 当pH值增大时,其与水的亲和力增大。     

共溶剂对反渗透复合膜表面形貌及分离性能的影响

以聚砜超滤膜为底膜,间苯二胺为水相单体,均苯三甲酰氯为有机相单体,通过界面聚合的方法制备了聚酰胺反渗透复合膜。研究了有机相共溶剂1,3-二甲基-2-咪唑啉酮、N,N-二甲基丙烯基脲、磷酸三丁酯对聚酰胺反渗透复合膜表面形貌及分离性能的影响。扫描电子显微镜观察表明,共溶剂的存在有助于复合膜表面形成"叶片状"结构;傅里叶变换红外光谱仪则对聚酰胺分离层化学结构进行了分析。通过改变共溶剂的种类和含量,可有效改变聚酰胺复合膜的表面形貌,最终调控膜的水通量和截留率。     

芳香聚酰胺反渗透复合膜界面聚合影响因素分析

目前应用较为广泛的反渗透复合膜的制备方法是由单体间苯二胺和均苯三甲酰氯在超滤支撑膜上界面聚合生成聚酰胺脱盐皮层。该制膜方法影响因素众多,能够影响反渗透复合膜分离性能的因素主要有支撑膜的结构和化学性质、单体结构和浓度、添加剂的选择、反应温度和时间、后处理温度和时间等。对界面聚合的一些主要影响因素进行分析。     

芳香聚酰胺系列反渗透复合膜的初步研究

本文研究了以芳香族聚酰胺为超薄层,聚砜多孔膜为支撑膜的反渗透复合膜,简要地讨论了成膜过程中的各种因素对膜性能的影响,如胺类和酰氯的种类、比例和浓度,以及反应时间等。探讨了膜性能与进料浓度的关系,膜的低压和耐氯性能及膜的电学性能和膜结构。实验表明选择不同胺类和酰氯,控制一定的成膜工艺条件,可制出具有各种不同反渗透特性的复合膜。     

反渗透复合膜研究进展与展望

反渗透技术凭借其高效率、操作维护方便等优点在近几十年得到长足的发展,并超越蒸馏等热法技术成为主流淡化技术。反渗透膜是反渗透技术的核心,其中芳香聚酰胺复合膜相比其他反渗透膜具有更高的通量和脱盐率、更好的耐压性和酸碱耐受范围,在反渗透技术中应用最为广泛。但聚酰胺类复合膜因较高的能耗,较弱的耐污性和较差的耐氯性,限制了其在海水淡化技术领域的发展,也成为研究人员关注的热点和和亟待解决的问题。随着新型功能性聚合物以及无机纳米材料的引入,反渗透复合膜的潜力被不断挖掘,研究人员进行了大量新型反渗透膜的制备研究,当前存在的问题有望得到解决。本文将分别针对聚酰胺反渗透膜的缺陷,结合反渗透技术和复合反渗透膜的研究现状,讨论新型反渗透膜的改进策略,并对其发展进行展望。     

用于反渗透复合膜的海绵状结构支撑膜制备研究

通过调节铸膜液中聚砜浓度和非溶剂含量,浸没沉淀法制备海绵状结构的支撑膜,并在支撑膜上界面聚合制备聚酰胺反渗透复合膜。分别对支撑膜及反渗透复合膜的结构和性能进行表征,考察聚砜浓度对支撑膜结构和性能的影响,以及不同结构支撑膜对反渗透复合膜结构和性能的影响。结果显示,随着聚砜浓度的增加,支撑膜表面孔径和孔隙率下降,断面结构变致密,耐压性增强。在不同支撑膜上制备的反渗透复合膜具有不同的通量和脱盐率。综合考虑支撑膜及反渗透复合膜的性能,以聚砜浓度为15%制备的海绵状结构支撑膜更适于作为制备反渗透复合膜的支撑层。     

TMC/TMPIP纳滤超薄复合膜的制备

基于哌嗪(PIP)与均苯三甲酰氯(TMC)界面聚合制备纳滤膜的原理,设计并合成了具有支化结构的三亚胺功能基团水相单体--均苯三甲酰哌嗪(TMPIP)盐酸盐,并与TMC界面聚合制得分子结构与TMC/PIP相同的TMC/TMPIP超薄纳滤复合膜。采用傅里叶红外光谱(FTIR)和扫描电镜(SEM)表征了复合膜皮层的化学结构和表面形貌,结果表明在聚砜底膜表面形成了膜厚为100 nm左右的TMC/TMPIP超薄皮层。通过与TMC/PIP复合膜对PEG 200水溶液的分离性能相比较发现,TMC/TMPIP复合膜因其高度的网络化结构和超薄皮层,因而具有更高的截留率和水通量。考察了TMC/TMPIP复合膜对水中不同盐的截留性能,其截留率顺序与TMC/PIP复合膜相同,而通量和截留率均优于后者。     

Ultra-thin skin carbon hollow fiber membranes for sustainable molecular separations

A transformative platform is reported to derive ultra-thin carbon molecular sieve (CMS) hollow fiber membranes from dual-layer precursor hollow fibers with independently tuned skin layer and substrate properties. These ultra-thin CMS hollow fiber membranes show attractive CO₂/CH₄ separation factors and excellent CO₂ permeances up to ~1,400% higher than state-of-the-art asymmetric CMS hollow fiber membranes. They provide a unique combination of permeance and selectivity competitive with zeolite membranes, but with much higher membrane packing density and potentially much lower costs.     

Study of synthesis parameters and active layer morphology of interfacially polymerized polyamide–polysulfone membranes

Thin film composite (TFC) polyamide membranes were prepared on a polysulfone support membrane and the effect of various synthesis conditions on the active layer morphology, the physicochemical properties and the membrane performance was investigated. The support membrane porosity factor had a significant effect on the TFC membrane performance. A polyamide top layer was formed within 15 s of reaction. Prolonging the reaction time, although resulting in a thicker active layer, only had a minor influence on the membrane performance. This highlights the importance of the incipient layer of the polyamide structure on its performance. The addition of both a surfactant and a base to the amine solution resulted in a change of the active layer morphology and an improved performance. The effect of additives was attributed to changes in the polymerization mechanism. In addition, it was demonstrated that curing at 50 °C resulted in an improved membrane performance, due to more cross-linking of the active layer. Curing at higher temperatures deteriorated the structure of the support membrane. This research shows that the TFC membrane performance is well correlated with the changes in the active layer morphology, measured using SEM, AFM and TEM; whereas only minor changes in the physicochemical characteristics of the membranes were detected by zeta potential and ATR-FTIR spectroscopy when the same synthesis parameters were varied.     

Selection of substrate manufacturing techniques of polyamine-based thin-film composite membranes for forward osmosis process

This paper is a comparative study on the preparation techniques used to make the support layer of polyamide-thin-film composite forward osmosis (TFC-FO) membranes. The role played by the support layer preparation technique in membrane performance is thoroughly investigated in this study. Electrospinning is shown to produce membranes of lower structural parameter compared to those obtained by conventional phase inversion techniques. The electrospun polyamide selective layer can also be tailored with the required properties. This makes electrospinning a promising process to design efficient FO membrane substrates. It is shown in this work that the FO water flux is more dependent on the internal structure of the support layer than the preparation materials. The main challenge remaining for substrates to operate in FO is to achieve simultaneously a low structural parameter, a high surface porosity, and the required mechanical properties. As most of today's approaches are not suitable, further materials development is essential in future investigations on TFC-FO membranes.     

Influence of binding interface between active and support layers in composite PDMS membranes on permeation performance

Effect of the binding interfaces of composite polydimethylsiloxane (PDMS) membranes on their pervaporation performance was studied. The membranes were made up of PDMS as active skin layer and polysulfone (PSF) or polyamide (PA) as supporting layer. PDMS‐PSF membrane was numbered 1, and PDMS‐PA membrane numbered 2. The pervaporation experiments were carried out by using the composite membranes and dilute ethanol–water mixture. The experimental measurements for the permeation performance under various operating conditions (e.g., feed concentration and temperature) showed that the specific permeation rate of membrane 2 was over membrane 1 by seven times at least. A resistance‐in‐series model was applied to formularize the transport of the permeants. Influence of the binding interfaces between the active skin layer and support layers in these membranes on pervaporation performance was analyzed. The cross section morphology of the membranes and chemical element distribution along membrane thickness were examined by using SEM and EDS. It was found that, although the PDMS intrusion layer into PSF near the interface was only about 2 μm, it gave significant effect on the permeation performance. It implied that the resistance produced by the intrusion layer into PSF was apparently larger than that of PDMS intruding PA and over intrinsic PDMS resistance. These should be probably attributed to structures and formation of the binding interfaces. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2468–2477, 2007     

Preparation and pervaporation performances of fumed‐silica‐filled polydimethylsiloxane–polyamide (PA) composite membranes

Fumed‐silica‐filled polydimethylsiloxane (PDMS)–polyamide (PA) composite membranes were prepared by the introduction of hydrophobic fumed silica into a PDMS skin layer. The cross‐sectional morphology of these filled composite membranes was observed with scanning electron microscopy. Their pervaporation performances were tested with aqueous ethanol solutions at 30, 35, and 40°C. Increasing the amount of the fumed silica resulted in significantly enhanced ethanol permeability of the membranes. When the content of the fumed silica in the PDMS skin layer was 20 wt %, the ethanol permeability increased to nearly twice that of the unfilled PDMS–PA composite membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Novel nanofiltration membranes with tunable permselectivity by polymer mediated phase separation in polyamide selective layer

Microstructure in selective layer has played a decisive role in permselectivity of nanofiltration (NF) membranes, and nanomaterials were well-known additives that had been applied to mediate the microstructure and permeability of polyamide NF membranes. However, nanoadditives generally displayed a poor dispersion in membranes or in fabrication process. To solve this problem, we showed an interesting concept that novel NF membranes with hybrid selective layer consisting of flexible polyisobutylene (PIB) and rigid polyamide could be fabricated from wel-defined interfacial polymerization. The hydrophobic polymer mediated phase separation and microdomains formation in polyamide layer were found. The immiscibility between the rigid polyamide and flexible PIB as well as the resultant interface effect was interpreted as the reason for the polymer enhanced permselectivity, which was similar with the well-known thin film nanocomposite (TFN) membranes that nanoparticles incorporated contributed significantly to membrane permeability and rejection performance. Our results have demonstrated that novel NF membranes with enhanced performance can be prepared from im-miscible polymers, which is a new area that has not been extensively studied before.     

Inhibiting the concentration polarization of FO membranes based on the wettable microporous supporting layer and the enhanced dense skin layer

A novel thin film composite‐type forward osmosis (FO) membrane with inhibited concentration polarization phenomenon and expectant separation performance was prepared by continuous interfacial polymerization method. The nylon‐6,6 microfiltration membrane with the average pore size of 5 μm and the self‐wetting property was for the first time used as the supporting layer of the FO membranes, which decreased the mass transfer resistance in the porous supporting layer. The skin layer was prepared via the continuous interfacial polymerization of polyamide as a relatively dense layer, with the reverse salt flux of less than 1 g/m^?2 h^?1. The mass transfer resistance and the reverse salt flux of the prepared FO membranes were remarkably reduced due to the functional design of the double‐layer structure, which effectively enhanced the separation selectivity and restrain the concentration polarization of the FO membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45133.     

Unexpected new phase detected in FT30 type reverse osmosis membranes using scanning transmission X-ray microscopy

FT30 type thin film composite membranes used for reverse osmosis water purification are very difficult to analyze. With the remarkably thin polyamide layer and surface modification of the polymers now being reported, a new analytical technique is needed to determine the surface structure and chemical distribution in the active layer. In this study we show that scanning transmission X-ray microscopy (STXM) can be used to determine the spatial distribution of polyamide and polysulfone and we report on the detection of an unexpected new phase. The new phase was identified as a homopolymer of the meta-phenylene diamine (MPD) that forms in MPD solutions and can be incorporated into the discrimination layer during the interfacial reaction with the TMC to produce a mixed polyamide polyMPD layer. The detection of this second phase was only made possible by STXM. At the levels detected in membranes in this study (less than 8%) the second phase had no effect on the flux or salt passage of the membranes, however at higher levels a change in the membrane properties most likely would occur and the quantity of the polyMPD present should be eliminated or controlled.     

Adsorption of perfluorinated compounds on thin‐film composite polyamide membranes

The adsorption behavior of perfluorinated compounds (PFCs), of various chain lengths and two different functional groups, on widely used thin‐film composite polyamide membranes has been investigated. Three commercially available polyamide membranes and two classes of PFCs were evaluated: Dow‐Filmtech BW30, NF90, and NF270 membranes; perfluorosulfonic and perfluoroalkanoic acid with 5, 7, 9, and 11 carbon atoms. The adsorption of PFCs on the membranes strongly depended on the active skin‐top layer material of the membranes, solution chemistry, and structure of PFCs. The piperazine based NF270 membrane showed higher adsorption of PFCs compared to BW30 and NF90 membranes (FT‐30 type membranes). The BW30 membrane, which has a coating layer of aliphatic carbons and hydroxyl groups on the surface of the polyamide substrate, had less interaction with PFCs than the NF90 polyamide membrane had. The adsorption of PFCs increased with increasing ionic strength, decreasing pH, and in divalent ion solutions. PFCs with longer chain lengths and more hydrophobic functional groups showed more attractive interactions with thin‐film composite membranes and, thus, greater adsorption on the membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012