渗透汽化-结晶耦合分离稀溶液中的香兰素

以聚醚嵌段共聚酰胺(PEBA2533)为膜材料,采用干法相转化法制备性能优异的高分子膜,用于渗透汽化-结晶耦合(PVCC)分离系统中回收稀水溶液中的香兰素。采用扫描电子显微镜(SEM)对PEBA2533膜的形貌进行表征。考察原料液浓度、温度对膜渗透汽化性能的影响。结果表明:随着溶液浓度的增加,PEBA2533膜溶胀性能增加,说明PEBA2533能够优先吸附香兰素;随原料液浓度增加,香兰素渗透通量增加,分离因子略微下降;原料液温度增加,香兰素渗透通量和分离因子都增加;并通过Arrhenius方程计算得到香兰素比水对温度更加敏感。PVCC系统中控制一级冷凝器温度为2℃时,一级冷凝器中结晶态香兰素通量为39.52 g·m~(-2)·h~(-1),纯度在99%以上。     

聚醚共聚酰胺复合膜制备及其在渗透汽化膜法脱盐中的应用研究

以亲水性聚醚共聚酰胺PEBA为分离层膜材料,采用浸渍涂覆法制备了具有较薄致密皮层的PEBA复合膜,并对其渗透汽化膜法脱盐性能进行了研究。在操作条件下,PEBA复合膜可获得5.6～51.3 L/（m2/h）的渗透液流量,盐截留率可达99%以上。随着原料液氯化钠质量浓度（0～70 g/L）的增大,渗透液流量减小,氯化钠截留率基本保持不变;随着操作温度的升高（30～70℃）,渗透液流量呈指数增大,渗透液流量和温度的关系满足阿伦尼乌斯方程,通过拟合计算得到纯水的表观活化能为26.8 kJ/mol,原料液中加入盐后,水的表观活化能略微升高,在27.5～29.8 kJ/mol。     

SiO_2-PEBAX/PAN膜渗透汽化分离吡啶

以聚醚共聚酰胺(PEBAX)为分离膜材料,聚内烯腈(PAN)超滤膜为支撑层,纳米气相二氧化硅(n-Si O2)颗粒为填充物,分别制备了PEBAX/PAN复合膜及n-Si O2-PEBAX/PAN填充型复合膜,旨在通过渗透汽化分离吡啶。采用扫描电镜(SEM)、X射线衍射(XRD)、傅里叶红外光谱(FT-IR)对复合膜进行表征,表明n-Si O2与聚合物只是物理混合。以吡啶/正庚烷混合物为模拟溶液,考察膜的溶胀及渗透汽化分离性能。溶胀实验结果表明:膜溶胀度随料液吡啶含量及温度的增加而增大。渗透汽化实验结果表明:n-Si O2填充量为10‰(wt)时总渗透通量最大,填充量为5‰(wt)时分离因子最大。总渗透通量和分离因子都随料液吡啶浓度增大而增加;渗透汽化操作温度升高,总渗透通量增大,而分离因子减小。当填充量为5‰(wt)、温度为30℃、以及料液吡啶含量为5000?g?g?1时,Pn5膜的总渗透通量为5.05 kg?m?2?h?1,分离因子为3.39。研究结果表明,Si O2-PEBAX/PAN复合膜对吡啶有较好的富集作用。     

聚醚共聚酰胺(PEBA)膜的溶胀和渗透汽化行为研究

用涂布法制备出PEBA均质膜,分别测试了膜在纯醋酸正丁酯、水以及醋酸正丁酯稀水溶液中的溶胀率,并考察了浸泡时间、温度和溶液浓度对溶胀率的影响;结果表明:PEBA膜在水中溶胀很小,对醋酸正丁酯具有优先吸附能力;溶胀率随浸泡时间的延长、浸泡液浓度和温度的升高而逐渐上升。渗透汽化实验表明膜对醋酸正丁酯的良好选择性,膜的渗透通量和分离因子随着浓度的增加而增加,渗透通量随着温度的升高而增加,但分离因子随温度的升高而减小;当原料液浓度为0.6%(wt)时,醋酸正丁酯的渗透通量为143.9g·m-2·h-1,分离因子达到236.9。     

含酚废水的渗透蒸发分离研究进展

含酚废水对环境有较大危害,近年来发展较快的渗透蒸发技术对含酚废水的处理较有潜力。论文综述了聚二甲基硅氧烷(PDMS)、聚氨酯(PU)和聚醚嵌段聚酰胺(PEBA)三类聚合物膜及其改性膜在渗透蒸发分离含酚废水方面的进展,并进行了比较,展望了含酚废水渗透蒸发分离的未来发展方向。     

渗透汽化分离乙酸的研究进展

渗透汽化作为一种新型的膜分离技术应用于乙酸的分离,可以优先透水或乙酸。特别是应用在发酵法制备乙酸等低酸含量溶液的分离中,可以优先透酸制备高纯度的乙酸,具有显著的优势。本文综述了渗透汽化技术在分离纯化乙酸中所涉及的膜材料、耦合工艺及其应用现状,并展望了其发展趋势。     

新型有机分离体系渗透汽化膜材料

综述了固载活性基团促进传递膜、新型共聚物和树枝型聚合物材料在提高膜的选择性与渗透通量中的作用.介绍了从分子结构角度设计的材料在提高分离效果与成膜稳定性中的应用,指出了新型高聚物膜材料在渗透汽化分离有机混合物领域具有较好的工业化应用前景.     

APTES改性ZIF-L/PEBA混合基质膜强化渗透汽化分离苯酚研究

渗透汽化(PV)膜分离是一种高效节能、无污染的化工分离技术,在有机废水处理领域的应用潜力巨大。以3-氨丙基三乙氧基硅烷(APTES)改性二维ZIF-L(AZLs),将其引入聚醚嵌段酰胺(PEBA)内制备AZLs/PEBA混合基质膜,用于分离水溶液中的苯酚。系统表征了所制膜的微结构与物化特性,考察了APTES添加量、AZLs填充量、操作温度、料液浓度等对膜分离性能的影响。结果表明：AZLs均匀分散在PEBA基质中,表明两者具有良好的界面相容性。AZLs的加入使得膜疏水性增强而表面自由能降低,从而提高了PEBA膜的选择性。当分离80℃、1000 mg/kg苯酚水溶液时,AZLs/PEBA膜总通量可达2046 g/(m²·h),分离因子为25.4,并且具有一定的稳定性。所制AZLs/PEBA混合基质膜在含酚废水处理方面具有应用前景。     

改性聚酰亚胺膜用于甲醇/甲基叔丁基醚的渗透汽化分离

本文以己二酸对聚酰胺羧酸进行改性，制得改性聚酰亚胺膜，用于甲醇／甲基叔丁基醚的渗透汽化分离。研究了制膜液浓度、己二酸含量、原料液组成及温度等条件对膜分离性能的影响，并分析了膜的结构与特征基团的光谱图。     

渗透汽化技术在液体分离中的研究新进展

渗透汽化是近年膜科学研究中最活跃的领域之一,在分离液体混合物,尤其是痕量、微量物质的移除,近、共沸物质的分离等方面有独特优势。简要介绍了渗透汽化技术的历史及发展过程,着重介绍了近几年渗透汽化技术在液体分离方面的研究进展。从研究结果来看,从水溶液中分离有机物研究主要集中在醇、酯的分离。在有机物脱水方面,开发出了选择性更好、渗透量更高的膜,乙醇脱水也有不少新的研究成果。特别是在有机混合物分离方面,取得了长足的进展,可以分离更多的有机物。     

Mass transfer of dilute 1,2‐dimethoxyethane aqueous solutions during pervaporation process

Pervaporation of 1,2‐dimethoxyethane (1,2‐DME) is evaluated by crosslinked oligosilylstyrene–poly(dimethylsiloxane) composite membranes. A low flow velocity of the feed solution (1.0 L/min), corresponding to a Reynolds number of 220, is used. The pervaporation models are developed by combining the resistance in series and solution–diffusion models. The effects of the boundary layer on the performance of pervaporation are estimated by comparing experimental and theoretical data. The permeation fluxes of 1,2‐DME and water fit very well with the calculated data from the models, but a deviation of the separation factor between the experimental and theoretical data is observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:2075–2084, 2006     

Separation of organic solvent from dilute aqueous solutions and from organic solvent mixtures through crosslinked acrylate copolymer membranes by pervaporation

The composite membranes of acrylate polymers and porous substrate were prepared. The separation of the organic solvent–water mixtures and the organic solvent–organic solvent mixtures through these membranes by pervaporation was investigated. The acrylate copolymer membrane showed the organic solvent permselectivity for the separation of the organic solvent–water mixture, especially for the chlorinated hydrocarbon–water mixture separation. The high organic solvent permselectivity should be governed by solubility selectivity. The influence of the ester residue of acrylate on the phenol–water mixture separation was observed. The copolymerization of the macromonomers containing the polystyrene, poly(methyl methacrylate), and polydimethylsiloxane chain had a small effect on the separation of the chlorinated hydrocarbon–water mixture. High flux and low selectivity of organic solvent were observed in the case of the organic solvent mixture separation through the n-butylacrylate membrane. The difference of permeability of organic solvent was observed for the acrylate copolymer which has various structures of ester residue. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 1483–1494, 1998     

Separation of aqueous phenol through polyurethane membranes by pervaporation. III. Effect of the methylene group length in poly(alkylene glycols)

Separation of phenol from dilute aqueous solution through polyurethane membranes by pervaporation was investigated. The effect of the methylene group length in poly(alkylene glycols) on permselectivity and solubility of phenol was studied. The poly(alkylene glycols) were obtained by polycondensation of 1,6‐hexanediol, 1,8‐octanediol, and 1,10‐decanediol with a sulfuric acid catalyst. Polyethyleneglycol and polytetramethyleneglycol were commercially available. Progress of the polymerization in the poly(alkylene glycols) was confirmed by FTIR, ¹H‐NMR analysis, and SEC measurement. The polyurethanes were obtained by polyaddition reaction of 1,6‐hexamethylenediisocyanate and the poly(alkylene glycol), and were confirmed by FTIR analysis and SEC measurement. The phenol concentration in a permeate liquid increased from 25.1 to 36.2 wt %, and the phenol partial flux also increased from 49.3 to 68.9 g · m⁻² · h⁻¹ with increasing the methylene group length in the poly(alkylene glycols), whereas the water partial flux slightly decreased. As a result of sorption measurements, the change in the degree of swelling was small, and the phenol concentration in the membrane increased from 42.1 to 70.8 wt %. The increase in the methylene group length of the poly(alkylene glycols) should contribute to an increase in the hydrophobicity of the polyurethane so that the solubility of phenol to the membrane should increase. The phenol concentration in the permeate liquid and the phenol partial flux increased with an increase in the methylene group length of the poly(alkylene glycols) due to the increase in the phenol solubility for the polyurethane membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 654–664, 2000     

Separation of aqueous organic liquid solutions through polymer membranes

Characteristics of permeation and separation for aqueous dimethyl sulfoxide, acetic acid and ethanol solutions through some polymer membranes such as chitosan, poly(vinyl chloride) and poly(dimethyl siloxane) membrane were studied by evapomeation. In temperature difference controlling evapomeation (TDEV), when the temperature of the feed solution was kept constant and the temperature of the membrane surroundings was changed, permselectivity for water increased in the chitosan and poly(vinyl chloride) membranes; in the poly(dimethyl siloxane) membrane the perm-selectivity for ethanol increased while decreasing the temperature of the membrane surroundings. Permeation and separation mechanisms for aqueous organic liquid solutions through the above polymer membranes by the TDEV method are discussed.     

水溶液中挥发性有机化合物渗透蒸发分离技术

介绍了水溶液中挥发性有机化合物 (VOCs)的各种分离方法 ,重点分析了渗透蒸发分离技术经济优势。阐释了渗透蒸发膜的选择标准、渗透蒸发过程的传质机理 ,以及原料液浓度、原料液温度、原料液流量、渗透侧压力、添加剂和膜组件型式等因素对渗透蒸发过程分离效率的影响 ,并简要预测了渗透蒸发过程的发展趋势与动态。     

Apparent specific volumes of polymers in dilute solutions

New results obtained on various polymers in solvents of differing molecular size and polarity confirm the dependence of their apparent specific volume ø₂ on polymer molecular weight and solvent molar volume. Existing models are discussed and a new model is proposed which assumes that ø₂ essentially depends on α, the expansion coefficient of the macromolecular coil, through the variation of the conformer sequence length in the chain. Some technical problems encountered with the vibrating tube densimeter are discussed.     

Separation of Phenol from Aqueous Streams by a Composite Hollow Fiber Based Pervaporation Process Using Polydimethyl siloxane (PDMS)/Polyether-Block-Amide (PEBA) as Two-Layer Membranes

Abstract

In order to simultaneously achieve both high permselectivity and permeability (flux) for the recovery of aromatic compounds such as phenol from aqueous streams, a composite organophilic hollow fiber based pervaporation process using PDMS/PEBA as two-layer membranes has been developed. The process employed a hydrophobic microporous polypropylene hollow fiber, having thin layers of silicones (PDMS) and PEBA polymers coating on the inside diameter. The composite membrane module is used to investigate the pervaporation behavior of phenol in water in a separate study; and that of a mixture of phenol, methanol, and formaldehyde in an aqueous stream (a typical constituent of wastewater stream of phenol-formaldehyde resin manufacturing process) in another study. The fluxes of phenol and water increase relatively linearly with increasing concentration especially at low feed concentration, and exhibit a near plateau with further increase in concentration. As a result, the phenol/water separation factor decreases as the feed concentration increases. Significant improvement in phenol/water separation factor and phenol flux is achieved for this two-layer (PDMS/PEBA) membranes as compared to that achieved using only PDMS membrane. The phenol and water fluxes and the separation factor are highly sensitive to permeate pressure as all decrease sharply with increase in permeate pressure. For this membrane, an increase in temperature increases the separation factor, and also permeation fluxes of phenol and water. An increase in feed-solution velocity does not have a significant effect on phenol and water fluxes, and also on the separation factor at least within the range of the feed-solution velocity considered. In the study of pervaporation behavior of a typical constituent of wastewater stream of phenol-formaldehyde resin manufacturing process, phenol permeation shows a much higher flux and a higher increase in flux with increase in concentration is also exhibited as compared to that exhibited by methanol permeation. This thus indicates that the membrane is more permeable to phenol than to methanol and formaldehyde.     

Removal of zinc from dilute aqueous solutions by galvanochemical treatment

The possibility of zinc removal, a common toxic metal, from simulated liquid effluents by the application of a novel treatment method, termed galvanochemical, was investigated. The galvanochemical process is considered as a simple, economic, friendly to the environment, method, which does not create harmful end‐products. Synthetic wastewaters were examined, these contained concentrations of zinc commonly found in real wastewaters from small‐to‐medium size industrial units, such as metal‐plating or metal‐treatment plants. These liquid wastes pose an important environmental problem, due to the content of heavy metals. The optimization of the main operating parameters was the objective of the study. The galvanic pair scrap ratio iron:coke was used for these investigations. It was found that the use of the galvanic pair mixture of 80 g dm^?3 (weight per solution volume ratio), agitated at 160 rpm for 5 h, removed more than 90% of zinc from the initial solution, containing initially 50 mg dm^?3 of zinc. The scanning electron microscopy/energy disperse spectrometry (SEM/EDS) analysis performed on the products showed that zinc was adsorbed onto the coke to a small extent and that the zinc removal was mainly based on the adsorption of zinc onto the surface of active iron oxides formed as a result of galvanochemical reactions. Copyright © 2005 Society of Chemical Industry     

Dynamic light scattering of dilute PVA-borax aqueous solutions

Poly(vinyl alcohol)-borate (PVA-borate) complexes in dilute aqueous solutions were investigated by dynamic light scattering (DLS). Two relaxation modes obtained, were scattering vector-q² dependent and diffusive. The amplitude of slow mode was independent of borax concentration. In the very dilute PVA concentration regime ( [PVA] < 5 g/L), the PVA di-diol-borate complexation was dominated by intra-molecular reaction, and the fast mode correlation length ς_f which corresponds to the polymer chain dimension increased rapidly with borax concentrations lower than 0.06 M, and reached an asymptote in the higher borax concentration regime. However, for a dilute PVA aqueous solution with higher PVA content (i.e., [PVA] = 9 g/L), both intra-and inter-molecular PVA di-diol-borate complexations might happen. The chain expansion and shrinkage of PVA-borate complex with increasing borax concentration was observed due to the balance between the electrostatic repulsion of the charged diol-borate complexes and the intra-molecular crosslink induced by the intra-molecular di-diol-borate complexation.     

Extraction of 1-butanol from aqueous solutions by pervaporation

The extraction of 1-butanol from fermentation broths by pervaporation offers potential for use in biotechnology. Various membrane materials have been screened for their suitability for this process. Polydimethylsiloxane (PDMS) membranes gave the best results in terms of flux and selectivity, with large variations depending on their nature and preparation. Selectivity was further increased by including either organophilic adorbents (cyclodextrins, zeolites), or oleyl alcohol in dense PDMS membranes. The predominance of driving force (i.e. activity gradient) on pervaporation extraction performances was shown by a comparative study on different binary aqueous solutions of alcohols. Water flux remained practically constant while the alcohol flux was linearly related to its feed concentration. The conclusions obtained with binary mixtures were consistent with those obtained with two model ternary solutions; the influence of salt on 1-butanol permeability was negligible, whereas ethanol had a strong effect.