基于两性离子的纳滤膜抗污染改性方法研究进展

纳滤膜对水中污染物的分离截留性能优异,膜污染控制和抗污染强化是该技术发展的研究热点。纳滤膜改性是强化纳滤膜抗污染性能的方法之一,基于两性离子材料的改性纳滤膜凭借两性离子材料静电作用与水分子结合的特性,在渗透性和抗污性方面表现优秀。系统综述了强化抗污染的两性离子纳滤膜的改性方法,包括涂覆法、接枝法、界面聚合法、自组装和共混掺杂法等,并阐释了各方法所制备纳滤膜的抗污效能和适用条件,最后对各改性方法做出了展望,以期为两性离子材料在纳滤膜改性和实际应用中的研究提供参考。     

两性离子二元胺单体的设计合成及其对哌嗪聚酰胺纳滤膜分离性能的影响

利用前驱体N,N-双（3-氨丙基）甲胺（BAMA）和1,3-二氨基-2-羟基丙烷（DAP）分别合成两种分子尺寸不同的两性离子二胺单体N,N-双（3-氨丙基）甲胺丙烷磺酸（BAMAPS）和2-N,N-二甲基丙二胺丙烷磺酸（DAPPS）,分别利用前驱体、两性离子二胺单体与PIP共同组成为水相溶液,与TMC通过界面聚合制备复合纳滤膜,并以二次界面聚合的方式将两性离子二胺单体引入到纳滤膜中。利用ATR/FTIR、SEM和接触角测定仪对膜进行表征,并考察单体结构,加入方式和单体含量对纳滤膜性能的影响。结果表明,前驱体、二胺基两性离子都被成功引入到纳滤膜的聚酰胺分离层中,随着水相组成中两性离子二胺单体含量增加,纳滤膜的亲水性增强,水通量提高而截留性能下降。BAMA和BAMAPS的分子结构较长,与分子长度较短的DAP和DAPPS相比,制备的纳滤膜水通量更高,截留性能下降。研究表明,侧基较长的二胺单体的位阻效应较强,使哌嗪聚酰胺链段形成大孔结构,导致无机盐截留率下降,水通量增加。结果表明,二胺单体的链长对于纳滤膜的渗透和分离性能有重要影响。     

氧化石墨烯改性复合纳滤膜的研究进展

氧化石墨烯(GO)掺杂到膜表面制备的GO-复合纳滤膜具有抗污染能力强、污染物截留率高的特点,是目前研究解决复合纳滤膜污染问题的热点。本文综述了GO-复合纳滤膜的材料选择和主要制备方法,并讨论了GO对GO-复合纳滤膜抗污染性能的影响,为进一步提高GO-复合纳滤膜抗污染性能的研究提供了理论依据和建议。     

改性纳滤膜处理镧离子稀土废水

研究以石墨烯量子点（GQDs）作为水相添加剂加入到哌嗪（PIP）水溶液中与均三苯甲酰氯（TMC）发生界面聚合反应制备复合纳滤膜,并用该膜处理镧离子稀土废水。通过正交实验确定制备改性膜的最佳比例质量分数为1.5% PIP、0.2% TMC、0.003% GQDs。在 30 ℃、0.6 MPa 条件下,改性纳滤膜对镧离子稀土废水的综合处理效果最好,长时间运行后改性纳滤膜的通量和截留率分别保持在 27.73 L/（m²·h）和 97.31%。有望为今后纳滤膜处理稀土尾矿水提供方向。     

氧化石墨烯改性聚乙烯醇纳滤膜的制备及性能研究

以聚砜超滤膜为支撑层,以聚乙烯醇为分离层材料,通过向聚乙烯醇中添加氧化石墨烯,制备了氧化石墨烯改性聚乙烯醇纳滤膜。分别以氯化钠溶液和硫酸钠溶液为原料液,测试了改性纳滤膜的分离性能,并与聚乙烯醇纳滤膜进行了对比。结果表明,与聚乙烯醇纳滤膜相比,氧化石墨烯改性聚乙烯醇纳滤膜的通量有一定下降,但对盐的截留率显著提高,对硫酸钠的截留率最高达96.1%,对氯化钠的截留率在30%左右,显示出较好的分盐性能。     

GO改性纳滤膜在富集回收稀土离子中的应用研究

离子型稀土乃国家战略资源,研究浸矿尾水中离子型稀土的富集回收具有重大意义。采用实验室自制的氧化石墨烯（GO）改性纳滤膜和未改性纳滤膜分别对浸矿尾水中离子型稀土进行富集试验。结果表明,两种膜在进料流量为5～6 L/min、操作压力为0.6～0.8 MPa时,对离子型稀土的富集呈现最佳状态,而且GO改性纳滤膜对离子型稀土的富集效果优于未改性纳滤膜。且在最佳操作条件下,未改性纳滤膜和GO改性纳滤膜的水通量分别为15.5～37.35、23.3～48.3 L/（m²·h）;两种纳滤膜对浸矿尾水中稀土离子的截留率分别可达73.4%～89.6%,82.3%～99.2%。通过抗污染性能研究得出,GO改性纳滤膜在持续运行16 h后的纯水通量恢复率约高出未改性纳滤膜16.6%,说明经过GO改性的纳滤膜拥有更强的抗污染性能。     

纳滤膜在染料工业脱盐浓缩中的应用

对CA50(醋酸纤维素)纳滤膜的盐截留率和染料截留率进行了考察,并将CA50纳滤膜应用于染料工业脱盐浓缩,考察了膜污染现象,对综合效益进行了分析。结果表明,CA50纳滤膜的盐截留率较低,对染料则有很高的截留率：将CA50纳滤膜应用于黄染料工业生产中,使主体染料的纯度提高20％,对黑染料膜分离过程进行优化,当盐浓度保持在5％时能获得最佳的脱盐效果;膜分离蓝色染料一段时间后,会造成膜污染,引起膜污染的物质主要是油污、无机物、有机物和染料分子,通过适当的预处理和清洗可以保持膜通量和防止膜污染：采用膜分离工艺使染料工业在经济、环境和社会效益得到提高．     

耐溶剂复合纳滤膜的研究进展

耐溶剂纳滤是一种新型的膜分离技术,用于有机混合物的分离。商品耐溶剂纳滤膜大多是采用相转化法制备的整体皮层非对称膜,膜皮层较厚,通量较低。耐溶剂复合纳滤膜由基膜和分离层组成,具有薄皮层、高溶剂通量和高溶质截留率的优点。耐溶剂复合纳滤膜的制备与改性也因此成为近年来的研究热点。本文从界面聚合、表面涂覆、层层自组装、原位生长、有机-无机杂化和表面改性六个方面介绍耐溶剂复合纳滤膜的研究进展,最后对其发展前景进行展望。     

温敏性抗污染纳滤膜的制备及性能表征

膜污染是制约纳滤膜发展应用的关键问题之一,表面改性是提高纳滤膜抗污染性能的有效途径。利用溶液浸涂工艺,将具有合适低临界温度(LCST)值和亲水性的温敏性聚N-异丙基丙烯酰胺(PNIPAm)类功能材料涂覆于聚酰胺纳滤膜表面对其进行修饰,制备出一种温敏性抗污染纳滤膜。测试结果表明,改性后的纳滤膜抗污染性能明显提高,死端过滤试验持续运行32h,通量衰减率只有8.7%,通量恢复率可达98.4%。     

丙烯酸接枝聚酰胺/聚醚酰亚胺复合纳滤膜的制备

为了提高复合纳滤膜的抗污染性能,采用紫外光照接枝法将丙烯酸接枝到聚酰胺/聚醚酰亚胺(PA/PEI)复合纳滤膜的皮层上,通过引入羧基基团来增加膜表面的亲水性。考察了丙烯酸单体质量分数、辐照时间对表面接枝率和膜分离性能的影响,并对优选的膜进行了抗污染性能测试。结果表明:丙烯酸质量分数与紫外辐照时间对膜分离性能的影响规律相同,膜通量随质量分数的增加与辐照时间的延长呈现先增加后减小的趋势,而截留率则保持基本不变,当丙烯酸质量分数2%,辐照时间2 min时,膜的通量达到13.12 L/(m2·h),较接枝前的11.94 L/(m2·h)略高;在含有1 g/L牛血清蛋白(BSA)的溶液中,接枝后的膜通量下降明显低于接枝前的膜。研究表明丙烯酸接枝可以有效改善膜表面亲水性,从而有利于提高膜的抗污染性能。     

Surface modification of polyamide nanofiltration membrane by grafting zwitterionic polymers to improve the antifouling property

A simple two‐step surface modification method of polyamide nanofiltration membrane, involving the activation of amide groups by formaldehyde and the subsequent cerium [Ce (IV)]‐induced graft polymerization of zwitterionic 3‐(methacryloylamino) propyl‐dimethyl‐(3‐sulfopropyl) ammonium hydroxide) (MPDSAH) monomers, was employed to improve membrane antifouling property. The membranes before and after modification were characterized by attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), scanning electron microscopy, and atomic force microscopy. The changes in both surface chemical composition and morphology of membranes confirmed the successful graft polymerizations of MPDSAH onto polyamide nanofiltration membrane. The static water contact angle measurements showed that surface hydrophilicity of the modified membranes was significantly enhanced. As the MPDSAH concentration increased, the water flux of grafted membrane decreased gradually, while salt rejection increased slightly. The fouling experiments with bovine serum albumin solution demonstrated that modified membranes exhibited better resistance to protein fouling. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41144.     

Preparation and characterization of carboxylated multiwalled carbon nanotube/polyamide composite nanofiltration membranes with improved performance

Polyamide thin‐film composite nanofiltration (NF) membranes were prepared via the interfacial polymerization (IP) process of piperazine and 1,3,5‐trimesoyl chloride on the polysulfone/nonwoven fabric ultrafiltration membrane surface. Carboxylated multiwalled carbon nanotubes (cMWNTs) were incorporated into the aqueous phase during the IP process to improve the membrane performance. The composition and morphology of the membrane surface were examined by means of attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy–energy dispersive spectrometry, and atomic force microscopy. The effects of the cMWNTs content on the membrane hydrophilicity, separation performance, and antifouling properties were characterized through water contact angle and crossflow filtration measurements. The experimental results show that membrane surface hydrophilicity, water permeability, salt rejection (R ), and antifouling properties all improved. In particular, when the cMWNTs content was 50 ppm, the magnesium sulfate R of the composite NF membrane reached a maximum value of 98.5%; meanwhile, the membrane obtained an obviously enhanced water flux (62.1 L m^?2 h^?1 at 0.7 MPa), which was two times larger than that of the original NF membrane. The modified NF membranes showed enhanced antifouling properties; this was mainly attributed to changes in the microstructures and surface features of the polyamide layer after the addition of the cMWNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45268.     

Zwitterionic monolayer grafted ceramic membrane with an antifouling performance for the efficient oil-water separation

Enormous demands on the separation of oil/water (O/W) emulsions in various industries, such as petrochemical, food and pharmaceutical industries, are looking for high performance and energy-efficient separation methods. Ceramic membranes have been used to deal with O/W emulsions, for its outstanding characteristics of easy-operation, high-flux, and long-term stability. However, membrane fouling is still a challenge in the industrial application of ceramic membranes. Herein, antifouling ceramic membranes were fabricated by grafting zwitterions on the membrane surface via an environment-friendly two-step grafting method, which improves the antifouling property and permeability. Successful grafting of such zwitterion on the ceramic surface was assessed by the combination of FTIR and XPS characterization. More importantly, the hydration can be formed by electrostatic interactions layer on the modified membrane, which was confirmed by TGA characterization. The antifouling performance of prepared zwitterionic ceramic membranes in the separation of O/W emulsions was systematically tested. The results suggested that zwitterion can significantly improve the flux of ceramic ultrafiltration membrane, and can also improve antifouling property dramatically by reducing the irreversible fouling in the separation of O/W emulsions. Therefore, zwitterionic ceramic membranes hold promising potentials as an antifouling, highly efficient and green method in the practical purification of the O/W emulsions.     

PAN ultrafiltration membranes grafted with natural amino acids for improving antifouling property

In this report, antifouling polyacrylonitrile (PAN) ultrafiltration membranes were prepared from blends of PAN/polyglycidyl methacrylate (PGMA) via phase inversion method followed by the grafting of natural amino acids through epoxy ring-opening reaction. The grafted PAN membranes possessed highly stable hydrophilic surfaces as a result of the grafting of amino acids, which was adequately demonstrated in attenuated total reflectance–Fourier transform infrared spectroscopy (ATR/FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of tensile strength and scanning electron microscopy (SEM) images further proved that the surface modification had little effect on their mechanical properties, surface, and cross-sectional morphologies. Meanwhile, remarkable resistance against bovine serum albumin (BSA) and lysozyme (Lyz) fouling was observed for the neutral amino acid-based PAN membranes due to the formation of zwitterionic hydration layer on the membrane surface, while PAN membranes grafted with charged amino acids were able to prohibit the approach of like charged proteins with reduced deposition and provide the driving force for oppositely charged protein adsorption. Furthermore, the ultrafiltration and antifouling performance of PAN membranes were investigated by BSA filtration experiments. Compared with the pristine PAN membrane, all the modified PAN membranes exhibited higher pure water flux, better flux recovery ratio, lower rejection, less total permeation resistance, and preferable stability, having potential applications in protein separation and purification.     

Recent developments in nanofiltration membranes based on nanomaterials

Nanofiltration membranes are the core elements for nanofiltration process. The chemical structures and physical properties of nanofiltration membranes determine water permeability, solute selectivity, mechanical/thermal stability, and antifouling properties, which greatly influence the separation efficiency and operation cost in nanofiltration applications. In recent years, a great progress has been made in the development of high performance nanofiltration membranes based on nanomaterials. Considering the increasing interest in this field, this paper reviews the recent studies on the nanofiltration membranes comprising various nanomaterials, including themetal andmetal oxide nanoparticles, carbon-based nanomaterials,metal–organic frameworks (MOFs),water channel proteins, and organic micro/nanoparticles. Finally, a perspective is given on the further exploitation of advanced nanomaterials and novel strategy for fabricating nano-based nanofiltration membranes. Moreover,the development of precision instruments and simulation techniques is necessary for the characterization of membrane microstructure and investigation of the separation and antifouling mechanism of nanofiltration membranes prepared with nanomaterials.     

Ionic liquid-induced deep grafting of polyelectrolyte to reform polyamide layer for antifouling nanofiltration membrane

Surface grafting has been widely used to tune hydrophilicity and chargeability of nanofiltration membranes for reducing membrane fouling potential. However, surface grafting typically leads to a significant pore narrowing and resultant permeability loss, and monocharged surface still struggles to resist mixed foulants with different charges. Herein, ionic liquid (IL)-ethanol (EtOH) solution containing polyethyleneimine (PEI) is used to rearrange the nascent polyamide layer. The high affinity of IL to the PA layer and the low diffusion steric hindrance of EtOH contribute to the polyamide swelling and PEI deep grafting, during which the “self-regulation” effect (larger pores would be filled with more PEI molecules) narrows the pore size distribution and enhances hydrophilicity. The nearly charge-neutral and smooth separation layer shows impressive antifouling capacity to hydrophobic macromolecules and mixed charged molecules, along with long-term operating stability for real wastewater treatment. This study emphasizes the importance of solvent properties on the membrane grafting behavior.     

单宁酸-多巴胺涂覆制备染料分离用纳滤膜

通过单宁酸及聚多巴胺涂覆,制备了单宁酸(TA)-聚偏氟乙烯(PVDF)纳滤膜,同时评价了改性膜对刚果红、伊文思蓝、活性嫩黄等染料的分离性能。结果表明,改性后膜表面粗糙度略微增大,亲水性明显增强。同时,改性膜具有水下超疏油的性质,能够完全抵抗水下油污的污染。2wt% TA-PVDF纳滤膜对多种染料的截留率能达到96.5%以上,且对刚果红、伊文思蓝、活性嫩黄等染料的截留通量都超过65.7 L/(m2?h?bar)。另外,改性膜在染料分离时截留通量基本不变,稳定性较强,在工业染料废水处理方面有一定的应用前景。     

Preparation and properties of hollow fibre nanofiltration membrane with continuous coffee-ring structure

Polyamide(PA)hollow fibre composite nanofiltration(NF)membranes with a coffee-ring structure and beneficial properties were prepared by adding graphene oxide(GO)into the interfacial polymerization process.The presentation of the coffee-ring structure was attributed to the heterogeneous,finely dispersed multiphase reaction system and the“coffee-stain”effect of the GO solution.When the piperazine concentration was 0.4 wt-%,the trimesoyl chloride concentration was 0.3 wt-%,and the GO concentration was 0.025 wt-%,the prepared NF membranes showed the best separation properties.The permeate flux was 76 L·m^?2·h^?1,and the rejection rate for MgSO4 was 98.6%at 0.4 MPa.Scanning electron microscopy,atomic force microscopy,and attenuated total reflectance-Fourier transform infrared spectroscopy were used to characterize the chemical structure and morphology of the PA/GO NF membrane.The results showed that GO was successfully entrapped into the PA functional layer.Under neutral operating conditions,the PA/GO membrane showed typical negatively charged NF membrane separation characteristics,and the rejection rate decreased in the order of Na2SO₄>MgSO₄>MgCl₂>NaCl.The PA/GO NF membrane showed better antifouling performance than the PA membrane.     

共混改性法对有机分离膜影响进展

有机聚合物如聚砜类、聚偏氟乙烯类、醋酸纤维素类、聚烯烃类等具有优良特性,是重要的膜材料。然而,膜污染问题限制了膜的应用。共混改性法操作简单,改性和成膜同时进行,效果稳定,通过共混改性法对有机聚合物膜进行膜改性可以有效降低膜污染。一方面通过共混亲水性聚合物、两亲性聚合物、两性离子聚合物对有机聚合物膜进行膜改性,制备改性膜的防污性和渗透性等性能均有不同程度的提升;另一方面,共混如TiO₂、SiO₂、碳纳米管（CNTs）、Al₂O₃、氧化石墨烯（GO）和ZrO₂等无机纳米粒子也可以制备高性能分离膜。本文从以上两方面综述了共混改性法的研究进展和存在的问题,并指出了通过共混改性提升膜的抗污染等性能是今后主要的发展趋势。