界面聚合在渗透汽化膜分离领域的应用进展

蒸馏、萃取等传统分离方法能耗高,污染环境,而渗透汽化由于低能耗、高效、环保等优势,为共沸物、近沸点混合物的分离提供了新的思路,但渗透汽化膜制备过程中面临的最大问题是获得性能优异且稳定的膜材料。在众多制备方法中,界面聚合法具有反应活性高、常温下生成膜层稳定、制备活性层致密等特点而备受关注。通过对界面聚合过程的调控,可以优化活性层,从而制备出兼具高通量和高选择性的渗透汽化膜。本文综述了界面聚合的原理、在渗透汽化膜制备方面的优势和近年来国内外的研究进展,详细阐述了复合膜制备过程中底膜的选择与改性、界面聚合条件的调控对渗透汽化膜结构和分离性能的影响机制,并对界面聚合制备渗透汽化膜所面临的问题及前景进行了总结与展望。     

抗污正渗透复合膜活性层的研究进展

归纳了基于不同方法-界面聚合、聚电解质层层组装、水通道蛋白仿生、双皮层设计构筑抗污正渗透复合膜活性层的优缺点,分析了膜表面物化性质与其正渗透及抗污性能之间的构效关系。认为支撑层的性质对活性层的形成及层间结合强度有显著影响;另外,平滑亲水及电中性或带与污染物相反电荷的活性层抗污性能更佳,选择合适的正渗透系统运行参数和清洗策略,可获得长期稳定的高水通量。未来除开发具低结构参数和优良物化性能的抗污支撑层,可针对目标污染物的尺寸及物化性质,进一步从活性层的设计和制备参数上进行简化、优化,均衡其渗透性和选择性,有效预防和改善膜污染,同时发展适配易回收的新型汲取液,充分发挥出正渗透的低能耗和耐污染优势。     

分离有机／有机混合物的PVA，CA系列膜及其渗透汽化性能研究（I）膜材料与成膜工艺

依据溶度参数原则和分离甲基叔丁基醚（MTBE）/甲醇（MeOH）混合物的选择渗透性,选择了聚乙烯醇（PVA）为复合膜的分离层材料,聚丙烯腈（PAN）、醛酸纤维素（CA）系列为支撑层的膜材料。初步讨论了膜材料和复合膜结构对分离性能的影响,给出了用不同成膜工艺制备的膜性能。获得了可用于有机/有机体系分离的性能优良的PVA/PAN和PVA/CA复合膜,以及CTA中空纤维渗透汽化膜。     

分离有机/有机混合物的PVA、CA系列膜及其渗透汽化性能研究(Ⅰ)膜材料与成膜工艺

依据溶度参数原则和分离甲基叔丁基醚(MTBE)/甲醇(MeOH)混合物的选择渗透性,选择了聚乙烯醇(PVA)为复合膜的分离层材料,聚丙烯腈(PAN)、醋酸纤维素(CA)系列为支撑层的膜材料.初步讨论了膜材料和复合膜结构对分离性能的影响,给出了用不同成膜工艺制备的膜性能,获得了可用于有机/有机体系分离的性能优良的PVA/PAN和PVA/CA复合膜,以及CTA中空纤维渗透汽化膜.     

静电纺丝法制备正渗透膜材料

通过静电纺丝法制备多孔纤维支撑层,再通过界面聚合法在其表面制备聚酰胺皮层,形成正渗透膜。首先,采用聚砜作为高分子材料,制备聚砜静电纺丝纤维支撑层,探究纺丝参数对纤维支撑层形态和性能的影响。然后采用聚偏氟乙烯为材料,通过静电纺丝法制备出纳米级蜘蛛网纤维结构的纤维支撑层,降低纤维支撑层的表面孔径,避免膜表面聚酰胺皮层的缺陷产生。最终界面聚合正渗透膜的NaCl截留率达到95%,并且具有较低的膜结构参数S值(2.23×10~(-4)m),减轻了正渗透过程中的内浓差极化程度。     

支撑层结构对PTFE-PDMS复合膜渗透汽化性能的影响

以不同结构的聚四氟乙烯(PTFE)平板膜为支撑层、聚二甲基硅氧烷(PDMS)为活性层,通过表面涂覆方法制备PTFE-PDMS复合膜,并用于渗透汽化过程,以实现乙醇-水混合溶液的分离;研究了支撑层结构及制膜参数对其分离性能的影响。结果表明,支撑层结构对复合膜分离因子几乎无影响,对孔径大孔隙率高的支撑层,制膜时,PDMS聚合物向支撑层中渗入过多会使复合膜的渗透通量降低。PDMS聚合物向支撑层渗透形成的过渡层是复合膜传质阻力的重要部分,且过渡层厚,复合膜的耐溶胀性好。综合考虑渗透通量及分离因子,复合膜优化制备条件是交联剂正硅酸乙酯的质量分数4%,交联温度80℃,交联时间为5 h。     

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。     

支撑层对硅橡胶复合膜渗透汽化分离性能的影响

引言 为了扩大渗透汽化技术的应用领域,科研工作者需要进一步增强渗透汽化膜的分离性能.从工业化的观点而言,用于实际应用的渗透汽化膜大多是复合膜,它由选择层(或分离层)和支撑层组成.一般认为,选择层决定着复合膜的选择性和通量,支撑层起支撑和机械稳定作用.Nijhuis[1]在从甲苯-水体系中分离甲苯的过程中对均质膜和以聚砜为支撑层的复合膜的分离性能进行了比较;Sturken[2]分别用聚醚酰亚胺和聚偏氟乙烯为支撑层的硅橡胶膜从二氯乙烷-水体系中提取二氯乙烷,他们得到了相同的结论:支撑层的影响可以忽略.然而Scholz[3],Heinzelmann[4],Rautenbach[5],Borges[6],Vankelecom[7],Farooq[8],Lipnizki[9]等均在各自研究中发现,由于基膜和分离层的物理化学性质以及制膜方法等众多因素的存在使得支撑层在一定程度上影响复合膜的分离性能;Feng[10]对均质硅橡胶膜和有微孔支撑层的硅橡胶复合膜的分离性能进行了比较,发现均质硅橡胶膜优先透过异丙醇,而有微孔亲水性支撑层的硅橡胶复合膜则优先透过水,这表明在一定的情况下,支撑层甚至起主导作用并能够决定复合膜的分离性能.因此,通过系统研究以不同多孔材料为支撑层的复合膜对有机物-水溶液的分离性能的影响,能够找到最优的复合膜支撑层,从而能够提高复合膜的分离性能.然而,至今关于支撑层对渗透汽化膜分离性能影响的系统研究仍相当少.     

聚酰胺薄层复合膜的界面聚合制备过程调控研究进展

界面聚合法制备的聚酰胺薄层复合膜凭借着渗透通量以及分离选择性高、化学稳定性佳等优点在水处理等领域有着广泛应用。聚酰胺分离层的物理结构和化学性质决定着复合膜的分离性能,通过调控界面聚合过程来优化聚酰胺层的理化性质可提高复合膜的分离性能。本文聚焦聚酰胺分离层性质与复合膜性能之间的关系,从基膜改性、调控单体反应过程、聚酰胺层后处理三个方面综述了近年来调控界面聚合制膜过程的研究进展。通过分析单体传质对界面聚合反应的影响以及膜结构与性能间的构-效关系,总结了界面聚合制备聚酰胺复合膜的调控机理和方法,为进一步提升聚酰胺复合膜的分离性能提供理论依据和发展方向。     

聚酰胺复合正渗透膜的制备及其脱盐性能研究

通过溶液相转化法制备四种基膜,然后采用界面聚合法制备不同基膜的聚酰胺复合正渗透(FO)膜,并对其结构与性能进行表征。结果表明,正渗透膜基膜表面开孔率高、孔径分布均匀,且纯水通量大;在基膜中引入聚酯(PET)筛网使其厚度增大、孔隙率和纯水通量降低。基膜材料为聚砜(PSF)时,复合膜聚酰胺分离层较为疏松,以聚偏氟乙烯(PVDF)为基膜材料,形成的分离层较为致密且具有典型峰谷结构,从而使反向盐通量更小。四种复合膜的正渗透纯水通量均大于10 L/m2·h,最高达20 L/m2·h。120 min连续正渗透脱盐实验表明,复合膜截盐率及其稳定性优于商用膜,尤其PET筛网支撑PVDF基复合膜的截盐率基本稳定在97. 5%左右,表现出良好的运行可靠性。     

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     

中空纤维渗透汽化膜分离研究现状与展望

本文综述了中空纤维渗透汽化膜分离的研究进展,包括中空纤维支撑膜的制备、复合膜的制备方法、中空纤维渗透汽化膜的工业应用和中空纤维渗透汽化膜传质特性等几个方面,对这个方面所存在的问题以及今后发展方向进行了展望.     

Novel interfacially-polymerized polyamide thin-film composite membranes: Studies on characterization, pervaporation, and positron annihilation spectroscopy

To improve the pervaporation performance of thin-film composite membranes, novel thin-film composite membranes were prepared via interfacial polymerization by reacting 5-nitrobenzene-1,3-dioyl dichloride (NTAC) or 5-tert-butylbenzene-1,3-dioyl dichloride (TBAC) with triethylenetetraamine (TETA) on the surface of a modified polyacrylonitrile (mPAN) membrane (TETA-NTAC/mPAN and TETA-TBAC/mPAN). The effect of the acyl chloride monomers chemical structure on the pervaporation separation of an aqueous ethanol solution was investigated. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water contact angle measurements were applied to analyze the chemical structure, surface chemical composition, surface roughness and hydrophilicity of the polyamide active layer of the composite membrane. To correlate the variations in the free volume of the polyamide active layers with the pervaporation performance, positron annihilation spectroscopy (PAS) experiments were performed with a variable monoenergetic slow positron beam. From the results of the PAS and XPS experiments, the S parameter, o-Ps annihilation lifetime τ₃ (corresponding to free volume size) and its intensity I₃ (corresponding to free volume concentration), the τ₃ and I₃ of TETA-NTAC polyamide layer (positron incident energy of 1-1.7 keV) were both higher than those of TETA-TBAC polyamide layer. The S parameter for TETA-NTAC polyamide layer was also higher than that of the TETA-TBAC polyamide layer even though the former was more crosslinking than that of the latter. In the aqueous ethanol solution dehydration experiments, the TETA-NTAC/mPAN membrane produced both a higher permeation rate and water concentration in the permeate than the TETA-TBAC/mPAN membrane.     

中空纤维渗透汽化复合膜及组件研究进展

中空纤维渗透汽化膜组件具有器件小型化及成本较低等方面的优势,其工业应用潜力巨大。本文介绍了中空纤维渗透汽化复合膜及组件的研究进展,阐述了膜材料、成膜方法以及组件结构参数等对组件渗透汽化性能的影响,并对中空纤维渗透汽化膜组件的中试研究进行了总结。通过组件放大及中试研究发现,中空纤维渗透汽化膜组件的装填密度、长度以及抽吸方式均会影响其下游侧的真空度,从而影响其渗透汽化性能。膜材料的分子设计、组件的结构参数优化以及耐溶剂耐高温封装将是中空纤维渗透汽化膜组件未来工业放大过程中的关键环节。     

Influence of support layer and PDMS coating conditions on composite membrane performance for ethanol/water separation by pervaporation

A systematic study was performed on the combination of support properties and polydimethylsiloxane (PDMS) coating conditions for the lab‐scale preparation of a defect‐free, thin film composite membrane for organophilic pervaporation. Support layers having comparable surface porosities were prepared from three polymers with different chemical composition (PVDF, PSF, PI). Their exact role on the deposition of the PDMS coating (i.e., wetting and intrusion) and the final membrane performance (i.e., effect on mass transfer of the permeants) was studied. The crosslinking behavior of dilute PDMS solutions was studied by viscosity measurements to optimize the coating layer thickness, support intrusion and wetting. It was found essential to pre‐crosslink the PDMS solution for a certain time prior to the coating. Dip time for coating the PDMS solution on the supports was varied by using automated dip coating machine. The performance of the synthesized membranes was tested in the separation of ethanol/water mixtures by pervaporation. Both flux and selectivity of the membranes were clearly influenced by the support layer. Resistance of the support layers increased by increasing the polymer concentration in the casting solutions of the supports. Increasing the dip time of the PDMS coating solution led to increased selectivity of the composite membranes. Scanning Electron Microscopy analysis of the composite membranes showed that this leads to a minor increase in the thickness of the PDMS top layer. Top layer thickness increased linearly with the square root of the dip time (t^0.5) at a constant withdrawal speed of the support. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43670.     

渗透汽化膜的制备及其应用进展

渗透汽化（pervaportion, PV）作为一种新颖的分离技术在工业范围内得以应用,至关重要的是它在恒沸混合物、近沸混合物分离方面的显著优势。相比分馏、精馏、萃取等传统分离方法,渗透汽化技术具有经济、高效、便于管理的优点,但目前缺少优质的渗透汽化膜材料和先进的膜制备方法。本文综述了近年来渗透汽化技术以及渗透汽化膜的研究现状,首先介绍了PV技术的分离机理、PV膜的制备方法、PV技术在工业上的应用领域等,并重点讨论了料液温度、料液浓度、料液流速、膜上下游蒸汽压差、膜材料等关键因素对渗透汽化分离性能的影响。文中提出未来渗透汽化技术应在膜材料方面积极探索,选用聚合物为材料,并结合先进的膜制备方法来进一步降低膜的厚度,从而明显地提高膜渗透通量。     

New nanocomposite materials made of an insulating matrix and conducting fillers: Processing and properties

The work described in this paper deals with the preparation and the characterization of an homogeneous composite material composed of electrically conductive fillers dispersed in a thermoplastic insulating matrix. These fillers were chosen to have either a spherical shape or a high aspect ratio. Processing of these conductive polypyrrole particles, which were obtained either through a classical polymerization of pyrrole in the presence of stabilizer, or polymerization onto the surface of cellulose monocrystals is detailed. The relationship of filler content in the composite to electrical and mechanical properties was investigated. In order to characterize the connectivity of the fillers in the matrix, electrical measurements were performed and these results have been compared with the predictions of the statistical percolation theory. Further analysis was undertaken by considering the influence of the network of rigid particles on the viscoelastic properties of the composites. These results were compared with two models; first, with a mechanical percolation approach which was based on strong interactions between fillers, and second, with a mean field model, which in no way accounted for interactions bewteen fillers. In recent developments, it has been shown that these materials used as coating on various substrate could be good sensors, allowing to determine some specific features of the substrate deformation.     

Pervaporation properties of a three‐layer structure composite membrane

A novel composite membrane with a three‐layer structure has been prepared. The top layer is a thin dense film of chitosan crosslinked with glutaraldehyde, and the support layer is made of microporous polyacrylonitrile (PAN). Between the dense and the microporous layer, there is an intermolecular crosslinking layer. The performance data show that this is an excellent pervaporation membrane for alcohol dehydration and one‐stage separation is attainable for some alcohol/water mixtures such as ethanol/water and isopropanol/water systems, which has a good separation factor of 1410 and a good flux of 0.33 kg m⁻² h⁻¹ for the EtOH/H₂O mixture, and 5000 and 0.43 kg m⁻² h⁻¹ for the i‐PrOH/H₂O mixture using 90 wt % alcohol concentration at 70°C.Using 90 wt % methanol aqueous solution at 60°C, a flux of 0.17 kg m⁻² h⁻¹ and selectivity of 123 are also obtained. The structure and performance of the novel composite membrane varies with conditions of membrane preparation, such as hydrolysis degree of PAN membrane, content of crosslinking agent, and heat‐curing temperature. The results indicate that the separation factor and the permeation rate of this novel composite membrane increase with the increase of operating temperature. At the same time, the pervaporation properties can be adjusted by changing the structure of the top layer and the middle layer. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 740–745, 2000