界面聚合法制备聚哌嗪酰胺复合纳滤膜

以聚醚砜超滤膜为基膜,哌嗪(PIP)为水相单体,均苯三甲酰氯(TMC)为有机相单体,采用界面聚合法制备了复合纳滤膜,扫描电镜、表层的红外分析结果表明在基膜表面聚合了一层聚酰胺膜,膜性能测定结果表明膜表面荷负电,对不同无机盐的截留率为Na2SO4MgSO4MgCl2NaCl。界面聚合条件对膜性能的影响表明,最佳聚合条件为:PIP浓度0.5%～2%,TMC浓度0.15wt%～0.75wt%,聚合时间≥1min,热处理温度60℃～80℃,时间15 min左右。     

单体结构对聚酰胺类复合膜分离性能的影响

采用间苯二甲酰氯、均苯三甲酰氯、均苯四甲酰氯分别与间苯二胺、乙二胺、哌嗪在耐高温杂萘联苯聚醚砜酮(PPESK)超滤膜表面进行界面聚合,制备了7种具有不同功能层结构的新型超薄复合膜.采用红外、X射线衍射、原子力显微镜等测试手段对复合膜结构进行表征,测试了7种复合膜对0.2%的Na2SO4水溶液,0.2%NaCl水溶液的分离性能,分析了单体结构与复合膜分离性能的关系.     

聚酰胺纳滤膜对黄连中生物碱的截留性能

以盐酸小檗碱为模型分子,考察循环时间、操作压力、料液浓度和离子强度等因素对聚酰胺纳滤膜截留盐酸小檗碱性能的影响。实验表明: 聚酰胺纳滤膜对盐酸小檗碱的截留率80min后基本稳定;随着操作压力的增加,膜通量和截留率都增大;随着料液浓度的增加,聚酰胺纳滤膜通量下降,对盐酸小檗碱的截留率先增大后下降;随着溶液中离子强度的增加,膜通量和截留率都减小。在黄连提取液中生物碱含量为0.025g/L、操作压力为0.4MPa条件下,聚酰胺纳滤膜5min可使黄连提取液中生物碱浓缩6.27倍。     

耐温高分子纳滤膜研究进展

耐温高分子纳滤膜在较高操作温度下具有稳定的分离性能,可应用于化纤、医药和食品等领域的分离纯化过程。本文总结了部分商品化纳滤膜的主要指标包括产水量、截留率和最高使用温度,综述了耐温高分子纳滤膜的制备方法、材料特性和应用领域等方面的最新进展。重点介绍了如何通过制备耐温基膜、设计合成新型分离层、引入纳米材料、增强界面反应以及调控界面聚合条件等策略来增强高分子纳滤膜的热稳定性。最后,对耐温高分子纳滤膜的研究进行了总结和展望。     

盐湖提锂纳滤膜研究进展

锂是我国发展新能源等产业的关键资源,进口依赖度大。盐湖提锂是应对锂短缺问题的重要途径,然而盐湖中高浓度的伴生镁离子给高效提锂带来挑战。纳滤膜可通过孔径筛分和电荷排斥效应的协同,有效分离镁锂离子,在盐湖提锂中扮演着重要的角色。本文从纳滤膜结构(孔径、电荷、厚度)调控出发,介绍了新单体设计、表面改性、共混掺杂、底膜改性等膜结构调控策略,阐述了膜结构与镁锂分离性能的构效关系,总结了不同制膜方法在镁锂分离过程中的优劣,展望了新型镁锂分离纳滤膜的研究方向。     

基于“可控”表界面工程的聚合物纳滤膜

复合纳滤膜凭借其效率高与能耗低的特点在分离膜领域占据着越来越重要的地位.但其制备所面临的最大挑战在于如何实现选择性皮层构建过程及结构性能的有效调控.通过\"可控\"的表界面工程可以实现对界面性质及界面反应速率的调控,从而实现复合纳滤膜的可控制备和性能提升.因此,我们提出通过\"\"可控\"聚合-界面沉积\"构建选择性皮层以实现复合纳滤膜分离层的创新制备和多功能化、基于\"基膜-单体溶液界面构建\"调控界面聚合以获得更薄分离层和更优异的纳滤性能.本文总结和评述了基于\"可控\"表界面工程的聚合物纳滤膜的重要进展,分析了该领域的未来研究方向,旨在为高性能复合纳滤膜的可控制备提供系统的方法学及理论支持.     

高分子量芳香共聚酰胺的合成

系统地对对苯二甲酰氯、对苯二胺和４，４′－二氨基二苯醚三元共缩聚体系低温溶液聚合的多种影响因素进行了研究，得到对数比浓粘度为５．８～７．０ｄｌ／ｇ的芳香共聚酰胺。实验结果表明：反应时间、反应温度、二酰氯与二胺的摩尔比、酸吸收剂吡啶用量、助溶盐氯化锂用量、４，４′－二氨基二苯醚用量以及单体浓度对共缩聚物的对数比浓粘度都有较大影响。     

氮气等离子体改性壳聚糖-聚丙烯腈复合纳滤膜

以氮气低温等离子体对壳聚糖-聚丙烯腈复合纳滤膜进行表面改性。用接触角、扫描电镜、扫描探针显微镜、X射线光电子能谱观察膜表面的亲水性和形貌特征,分析膜表面化学组成;以γ-氨基丁酸为分离对象表征膜的纳滤性能。结果表明:经50 W、20 Pa的氮气等离子体作用2 min,壳聚糖膜表面的亲水性大幅改善,其接触角由102.0°下降至44.3°,平整度明显提升;膜表面中的C—C、C—O和酰胺基团均减少,而胺基和羰基相应增加;在pH=6.15的水溶液中对w=1.0%的γ-氨基丁酸进行纳滤,液体通量由原来的1.12 L/(m~2·h)提高至1.75 L/(m~2·h),且对氨基酸的截留率从28%提升至83%。     

动电法研究聚酰胺类纳滤膜界面电现象

以DK膜为研究对象,以透过式流动电位测试系统为分析手段,采用动电法研究聚酰胺类纳滤膜的界面电现象。根据Helmholtz-Smoluchowski方程和Gouy-Chapman模型系统地考察了电解质溶液浓度和离子种类、价态等因素对膜ζ电位和电荷密度的影响。研究发现,在一定浓度范围内,DK型纳滤膜的电荷密度与电解质溶液浓度之间符合Freundlich吸附等温式,其中对于Na2SO4溶液:ln|σ|(mC/m2)=2.436 0.505lnC(mol/m3);对于MgSO4溶液:ln|σ|(mC/m2)=-0.539 1.412lnC(mol/m3);对于KCl溶液:ln|σ|(mC/m2)=-0.140 0.280lnC(mol/m3);对于CaCl2溶液:ln|σ|(mC/m2)=-2.287 1.105lnC(mol/m3)。结果表明,电解质溶液中阴离子的特性吸附是聚酰胺类纳滤膜荷电现象产生的主要原因。     

三甲基苯二胺芳香聚酰胺的结构与性能

利用ＩＲ，ＷＡＸＤ，ＤＳＣ及ＴＧ等表征了多取代芳香族聚酞胺的结构与性能。     

Influence of the polyacyl chloride structure on the reverse osmosis performance,surface properties and chlorine stability of the thin-film composite polyamide membranes

This paper aims to study the structure–property relationship and make several reasonable suggestions for tailoring special separation performance and surface properties of thin-film composite polyamide membranes. In the experiments, composite membranes of different thin films with small structural differences were prepared through interfacial polymerization of trimesoyl chloride (TMC), 5-isocyanato-isophthaloyl chloride (ICIC), and 5-chloroformyloxy-isophthaloyl chloride (CFIC) with m-phenylenediamine (MPD) separately, after which their reverse osmosis performances were evaluated by permeation experiment with salt aqueous solution, and film properties were characterized by AFM, SEM, XPS, ATR-IR, contact angle and streaming potential measurements. Chlorine stability was also studied through the evaluation of membrane performance before and after hypochlorite exposure. The results show that the polyacyl chloride structure strongly influences the reverse osmosis performance, surface properties and chlorine stability of the composite membranes; that the introduction of isocyanato group into polyacyl chloride improves the hydrophilicity, water permeability and surface smoothness of the thin-film composite membrane, and increases the absolute value of zeta potential at both low and high pH, but reduces the chlorine stability; and that the introduction of chloroformyloxy group increases the salt rejection rate and the surface roughness of the composite membrane, but lowers the water permeability.     

PES中空纤维复合纳滤膜的制备

采用界面聚合法制备聚醚砜（PES）中空纤维复合纳滤（NF）膜,讨论了制备条件对PES中空纤维复合NF膜性能的影响。实验结果表明,聚合反应时间、均苯三甲酰氯浓度、哌嗪浓度和酸吸收剂三乙胺浓度对复合NF膜性能有显著影响,同时二次反应能够提高复合NF膜的截留率,对2g／L的Na2SO4截留率可达到99．2％。     

Interfacially polymerized thin film composite membranes on microporous polypropylene supports for solvent-resistant nanofiltration

Interfacial polymerization (IP) is a powerful technique for fabrication of thin film composite (TFC) membranes. The polymers used most often as support are polysulfone (PS) or polyethersulfone (PES). These supports have limited stability in organic solvents. In this work, microporous polypropylene (PP) flat film and hollow fiber membranes were used as a support to fabricate TFC membranes for nanofiltration by the IP technique. Porous polypropylene membranes can provide substantial chemical, pH, and solvent resistance and are therefore suitable as supports for fabricating TFC membranes functioning as solvent-stable nanofiltration membranes. The surface and the pore interior of polypropylene flat sheet and hollow fiber membranes were hydrophilized first by pre-wetting with acetone followed by oxidation with chromic acid solution. A standard procedure to successfully coat the hydrophilized flat film and hollow fiber membranes was developed next. The monomeric system chosen for IP was poly(ethyleneimine) and isophthaloyl dichloride. The TFC hollow fiber membranes were characterized by nanofiltration of safranin O (MW 351) and brilliant blue R (MW 826) dyes in methanol. Rejection values of 88% and 43% were achieved for brilliant blue R and safranin O, respectively at a transmembrane pressure of 413 kPa in the TFC hollow fiber membranes. Pressure dependences of the solvent flux and solute rejection of the TFC membranes were studied using the modified flat sheet membranes up to a pressure of 965–1241 kPa. Solvent flux increased linearly with an increase in the transmembrane pressure. Solute rejection also increased with an increase in the transmembrane pressure. All modified membranes were also characterized using scanning electron microscopy. Extended-term solvent stability of the fabricated membranes was studied in toluene; the membranes demonstrated substantial solvent stability in toluene.     

High flux nanofiltration membranes based on interfacially polymerized polyamide barrier layer on polyacrylonitrile nanofibrous scaffolds

Electrospun polyacrylonitrile (PAN) nanofibrous scaffold was used as a mid-layer support in a new kind of high flux thin film nanofibrous composite (TFNC) membranes for nanofiltration (NF) applications. The top barrier layer was produced by interfacial polymerization of polyamides containing different ratios of piperazine and bipiperidine. The filtration performance (i.e., permeate flux and rejection) of TFNC membranes based on electrospun PAN nanofibrous scaffold was compared with those of conventional thin film composite (TFC) membranes consisting of (1) a commercial PAN ultrafiltration (UF) support with the same barrier layer coating and (2) two kinds of commercial NF membranes (i.e., NF90 and NF270 from Dow Filmtec). The nanofiltration test was carried out by using a divalent salt solution (MgSO₄, 2000 ppm) and a cross-flow filtration cell. The results indicated that TFNC membranes exhibited over 2.4 times more permeate flux than TFC membranes with the same chemical compositions, while maintaining the same rejection rate (ca. 98%). In addition, the permeate flux of hand-cast TFNC membranes was about 38% higher than commercial NF270 membrane with the similar rejection rate.     

Study on the thin-film composite nanofiltration membrane for the removal of sulfate from concentrated salt aqueous: Preparation and performance

Thin-film composite (TFC) nanofiltration (NF) membrane was prepared through the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC) on the polysulphone support membrane. The chemical structure of membrane surface was studied by attenuated total reflectance infrared (ATR-IR) and X-ray photoelectronic spectroscopy (XPS). Parametric studies were conducted by varying reaction time, curing temperature, curing time and additives in PIP solution for obtaining the optimum polymerization conditions. Systematic performance studies were conducted with different feed solutions, feed concentrations, feed pHs, operating temperatures and pressures. Continuous and comparative tests were also conducted to determine the performance stability and separation efficiency of the thin-film composite NF membrane prepared. High performance thin-film composite NF membrane for the selective sulfate removal from concentrated sodium chloride aqueous with the water permeability coefficient of 75 L/(m² h MPa) could be prepared under specific conditions. Experimental results on concentrated mixed solution of NaCl and Na₂SO₄ demonstrated that the NF membrane developed could be successfully used for the removal of sodium sulfate from the concentrated brine of chloralkali industry with high permeate flux, selectivity and performance stability.     

Preparation of Composite Charge-mosaic Hollow Fiber Membrane by Interfacial Polymerization

The preparation of composite charge-mosaic membrane included spinning of hollow fiber as the supporting membrane, preparing a selective layer on the inside surface of the fiber by interracial polymerization. The charge-mosaic membranes show a high salt permeability while retaining sucrose. The charge-mosaic membrane can be effectively used to separate multivalent salts with organic matter of molecular weight great than 300g/mol in industry.     

Influence of rupture strength of interfacially polymerized thin-film structure on the performance of polyamide composite membranes

The permeation properties of a thin-film composite (TFC) membrane depend upon the material properties as well as the structural properties of the polymer forming the active layer. Membranes with the active layers prepared with 1,3,5-benzentricarbonyl chloride (TMC) and aliphatic diamines including dimethylenediamine (DMDA), 1,6-hexamethylenediamine (HMDA), and 1,9-nonamethylenediamine (NMDA) exhibit inferior performance compared to membranes with active layers composed of aromatic diamines including 1,3-benzendiamine (MPDA) and 1,4-benzendiamine (PPDA). It is also observed that the water flux for these membranes decreases as the length of the methylene chain increases due to decreasing hydrophilicity. Furthermore, because of the low rupture strength of the thin-films that form the active layer, the salt rejection also decreases with increasing methylene chain length. The membranes prepared with MPDA and various acyl chlorides including 1,6-hexamethylenedicarbonyl chloride (SC), 1,3-benzenedicarbonyl chloride (IPC), and 1,4-benzene dicarbonyl chloride (TPC) have low rupture strength and poor performance characteristics except for the membrane having network structure, TMC. It is observed that while hydrophilicity has a small effect on the permeation performance of the thin-films its effect of the rupture strength is large. Membranes with weak rupture strength evidence low salt rejection. Hence, the permeation performance of composite membranes with thin-films having weak mechanical strength at high operating pressures depends upon not only the physicochemical properties of the active material including the chemical properties, but also the mechanical strength of the polymer comprising the thin-film.     

Effects of the polyamide molecular structure on the performance of reverse osmosis membranes

Thin-film composite reverse osmosis membranes of polyamides were prepared by interfacial polymerization. Various benzenediamines and poly(aminostyrene) were interfacially reacted with various acyl chlorides to prepare a skin layer of composite membranes. Among the membranes prepared from the structural isomeric monomers of benzenediamines and acyl chlorides, i.e., the same chemical composition but different in the position of functional groups on the aromatic ring, the membrane with the best salt rejection was obtained when the reacting groups forming amide are located at the same position on the aromatic ring. Membranes prepared by interfacially reacting various diamines with trimesoyl chloride revealed that the salt rejection depends on the linear chain structure of polyamides and network formed by crosslinking. Membranes obtained by interfacial polymerization of poly(aminostyrene) with trimesoyl chloride showed higher water flux but lower salt rejection than those obtained by interfacial polymerization of various benzenediamines with trimesoyl chloride. Membranes obtained here showed the typical trade-off behavior between salt rejection and water flux. However, membranes prepared by interfacially reacting trimesoyl chloride with a mixture of poly(aminostyrene) and m-phenylenediamine or a mixture of poly(aminostyrene), m-phenylenediamine, and diaminobenzoic acid showed a performance advantage over usual membranes, i.e., a large positive deviation from the usual trade-off trend. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 1821–1830, 1998     

On the prediction of permeate flux for nanofiltration of concentrated aqueous solutions with thin-film composite polyamide membranes

The nanofiltration of binary aqueous solutions of glucose, sucrose and sodium sulfate was investigated using thin-film composite polyamide membranes with different molecular weight cut-off's. The NF experiments, in total recycle mode, were performed in a plate-and-frame module Lab 20 (AlfaLaval), at 22 °C and with a flowrate of 8.2 L/min, using the membranes NF90, NF200 and NF270 from FilmTec (Dow Chemical), for transmembrane pressures between 1 and 6 MPa and with aqueous solutions with osmotic pressures of between 0.5 and 3.0 MPa. The permeate flux was predicted by the osmotic pressure model, using the membrane hydraulic resistance and the solution viscosity inside the membrane pores, and computing the concentration polarization with recourse to a mass-transfer correlation specific for the plate-and-frame module used. The flux predictions, using the pure water viscosity, agree reasonably with the experimental data only for low transmembrane pressures and with the most diluted solutions. For higher transmembrane pressures and for higher solute concentration the predicted fluxes can be as far as 2.5, 4.1 and 9.6 times higher than the experimental one, for the aqueous solutions of Na₂SO₄, glucose and sucrose, respectively. These deviations are strongly reduced when the pure water viscosity is replaced by the solution viscosity adjacent to the membrane. In this case, the maximum deviation between predictions and experiments occurs also for higher transmembrane pressures and for higher solute concentration, but the maximum ratio between predicted values and the experiments were reduced now to 1.8, 2.1 and 2.9, for the aqueous solutions of Na₂SO₄, glucose and sucrose, respectively. Even using the solution viscosity adjacent to the membrane, and for the systems investigated, the osmotic pressure model must used with caution for design purposes because it may over predict the permeate flux by a factor of about 2 when the solute concentration is high.