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1.
Blended chitosan and polyvinyl alcohol membranes for the pervaporation dehydration of isopropanol 总被引:2,自引:0,他引:2
A. Svang-Ariyaskul R.Y.M. Huang P.L. Douglas R. Pal X. Feng P. Chen L. Liu 《Journal of membrane science》2006,280(1-2):815-823
Homogeneous membranes were prepared by casting the solution of blended chitosan and polyvinyl alcohol (PVA) on a glass plate. The percent weight of chitosan in the membrane was varied from 0 to 100%. The membrane thickness was in the range of 15–30 μm. The membranes were heat treated at 150 °C for an hour. After that the membranes were crosslinked by glutaraldehyde and sulfuric acid in acetone aqueous solution. The membranes were tested at 30–60 °C for dehydration performance of 50–95% isopropanol aqueous solutions. At around 90% of isopropanol in the feed mixture, permeate flux increased whereas the percent of water in permeate tended to decrease when the feed temperature increased for all membranes, except that the water content in permeate from the membrane containing 75 wt.% chitosan remained constant. The swelling degree in water and the total flux increased with increasing chitosan content in membranes. The effect of temperature on permeate flux followed the Arrhenius relationship. The permeate flux decreased when isopropanol in the feed increased for all membranes. However, water content in permeate and isopropanol concentration in the feed formed complex relationship for different chitosan content membranes. Sorption did not appear to have significant effects on separation. The membrane containing chitosan 75% performed the best. For a feed solution containing 90% isopropanol at 60 °C, the permeate flux was 644 g/m2 h with water content of nearly 100% in the permeate. At 55% isopropanol in the feed at 60 °C, the permeate flux was 3812 g/m2 h. In the range of 55–95% of isopropanol in the feed, the water content in permeate was more than 99.5%. This membrane showed very excellent performance with good mechanical strength. It is promising to develop this membrane for industrial uses. 相似文献
2.
P.S. Rachipudi A.A. Kittur S.K. Choudhari J.G. Varghese M.Y. Kariduraganavar 《European Polymer Journal》2009,45(11):3116-3126
Using a solution technique, chitosan-based polyelectrolyte complexes (PECs) were developed as pervaporation membranes by incorporating phosphotungstic acid (PTA). The resulting membranes were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Membranes were tested for their ability to separate water–isopropanol mixtures by pervaporation in the temperature range of 30–50 °C. The experimental results demonstrated that both flux and selectivity were increased simultaneously with increasing PTA content in the membrane. The permeation flux of pure chitosan membrane was increased dramatically from 4.13 to 11.70 × 10−2 kg/m2 h and correspondingly its separation factor was increased from 4490 to 11,241 and then decreased to 7490 at 30 °C for 10 mass% of water in the feed. The total flux and flux of water were found to be almost overlapping particularly for PECs membranes, suggesting that these could be used effectively to break the azeotropic point of water–isopropanol mixtures. From the temperature dependency of diffusion and permeation values, the Arrhenius activation parameters were estimated and discussed in the context of membranes efficiency. The pure chitosan and a small amount of PTA-incorporated PECs membranes exhibited positive heat of sorption while other PECs membranes exhibited negative heat of sorption, giving exothermic contribution. 相似文献
3.
《Journal of membrane science》1999,156(1):17-27
Novel two-ply dense composite membranes were prepared using successive castings of sodium alginate and chitosan solutions for the pervaporation dehydration of isopropanol and ethanol. Preparation and operating parameters namely polymer types facing to the feed stream, NaOH treatment for the regeneration of chitosan, and crosslinking system types were investigated using the factorial design method. It was shown that these parameters were all critical to the performance of the membrane in the form of the main and interaction effects. The pervaporation performance of the two-ply membrane with its sodium alginate layer facing the feed side and crosslinked or insolubilized in sulfuric acid solution was compared with the pure sodium alginate and the chitosan membranes in terms of the flux and separation factors. It was shown that although its flux was lower than that of the pure sodium alginate and chitosan membranes, the separation factors at various alcohol concentrations were in between values for the two pure membranes. For the dehydration of 90 wt% isopropanol–water mixtures the performance of the two-ply membrane which was moderately crosslinked in formaldehyde was found to match the high performance of the pure sodium alginate membrane. This two-ply membrane had fluxes of 70 g/m2 h at 95% EtOH, 554 g/m2 h at 90% PrOH and separation factors of 1110 at 95% EtOH, 2010 at 90% PrOH and its mechanical properties were better than that of the pure sodium alginate membrane. 相似文献
4.
Composite membranes with a sub-nanoscale homogeneous distribution of CD toroids in the Matrimid matrix were developed for dehydration of aqueous isopropanol. The composite membranes demonstrated separation factor far surpassing that of the neat Matrimid dense membrane. The heart of this innovation is the utilization of a CD derivative, ethylenediamine-β-cyclodextrin (EDA-β-CD), where the amine of CD could react with the imide of Matrimid and efficiently immobilize the CD rings during membrane formation. The superior separation properties for membranes embedded with 2–5% EDA-β-CD were attributed to the additional water channels created by the hydrophilic outer surface of CD and its interactions with the polymer matrix. FT-IR, density measurements and XRD have confirmed these hypotheses. Nevertheless, the separation factor exhibited an increasing then decreasing trend as a function of CD content and the opposite trend was observed with permeation flux. Investigation on the effect of feed water concentration showed that the neat Matrimid membrane possessed almost constant performance, but the Matrimid/EDA-β-CD (0.05) composite membrane exhibited an obvious increase in permeability and a decrease in selectivity at high water content. Even though the composite membrane swelled more at higher water content due to the intensified hydrophilicity ascribed to the introduction of CD structure, it always had much better separation factor. In addition, the Matrimid mixed matrix membranes embedded with 2–5% EDA-β-CD held reasonably tensile strength and modulus. The newly developed mixed matrix membrane approach may open up a new way to prepare next-generation high-performance asymmetric pervaporation membranes for isopropanol separation. 相似文献
5.
《Journal of membrane science》2001,193(1):85-95
A novel organic dehydration membrane consisting of aminated polyacrylontrile (PAN) microporous membrane as sublayer, alginate coating as top layer has been prepared and characterized by pervaporation experiment. The influence of hydrolysis and amination of the microporous support layer on selectivity and flux was studied and it was shown that amination of the sublayer improved pervaporation performance of the composite membrane greatly. The counter cation of alginate coatings as dense separating layer also influenced separation properties of the membrane, which was better for K+ than for Na+. This novel composite membrane with K+ as counter ion has a high separation factor of 1116 and a good permeation rate of 350 g/m2 h for pervaporation of 90 wt.% ethanol aqueous solution at 70°C, higher separation factors and fluxes for n-PrOH/water, i-PrOH/water, acetone/water and dioxane/water systems. The results show that the separation factor and flux of this membrane increase with raising the operating temperature. At the same time, SEM micrographs show that the hydrolysis and amination of PAN microporous membrane change its pore structure. From the results it can be concluded that pore structure of the sublayer in addition to its chemical structure also make influence of separation properties of the composite membrane. 相似文献
6.
B. Vijaya Kumar Naidu Malladi Sairam K.V.S.N. Raju Tejraj M. Aminabhavi 《Journal of membrane science》2005,260(1-2):142-155
Novel nanocomposite polymeric membranes containing nanosized (30–100 nm) polyaniline (PANI) particles dispersed in poly(vinyl alcohol) (PVA) were prepared and used in the pervaporation separation of water–isopropanol feed mixtures ranging from 10 to 50 mass% of water at 30 °C. Of the three nanocomposite membranes prepared, the membrane containing 40:60 surface atomic concentration ratio of PANI:PVA produced the highest selectivity of 564 compared to a value of 77 observed for the plain PVA membrane. Flux of the nanocomposite membranes was lower than those observed for the plain PVA membrane, but selectivity improved considerably. Membranes were characterized by differential scanning calorimetry, dynamic mechanical thermal analyzer, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The highest selectivity with the lowest flux was observed for 10 mass% water containing feed mixture. Flux increased with increasing amount of water in the feed, but selectivity decreased considerably. These results were attributed to the acid-doped PANI particles in the PVA membrane as a result of change in the micromorphology of the nanocomposite membranes. In addition, molar mass between cross-links and fractional free volume of the membranes are responsible for the varying membrane performance. Temperature effect on permeability was investigated for 10 mass% water containing feed with the membrane containing higher concentration of PANI particles, the presence of which could be responsible for varied effect of water permeation through the membrane. Membranes of this study could remove as much as 98% of water from the feed. 相似文献
7.
A. S. Araujo M. J. B. Souza V. J. Fernandes Jr. J. C. Diniz 《Reaction Kinetics and Catalysis Letters》1999,66(1):141-146
The catalytic dehydration of isopropanol has been studied over a solid acid silicoaluminophosphate type SAPO-5. The reaction
was processed varying the temperature and weight hourly space velocity, using a fixed bed continous flow reactor. The isopropanol
undergoes inter- and intramolecular dehydration, forming propylene and isopropyl ether, respectively. Nevertheless, the catalyst
was selective to the olefin, with an activation energy of the order of 46.1 kJ/mol. 相似文献
8.
Pervaporation properties of chitosan films in a basic form prepared from thermally modified chitosan acetate in a salt form with respect to aqueous-organic media are studied. It is found that thermally treated films of smaller surface areas have higher permeability and selectivity than the initial chitosan film. A tenfold increase in the membrane surface area leads to a manyfold decrease in a permeate flux density through a thermally treated membrane as compared with an initial membrane and to the appearance of inverse selective permeability upon variations in a liquid phase composition. The results obtained are compared with the previous data. It is concluded that swelling complex polymeric materials are characterized insufficiently for explanation of specific transport properties with respect to low-molecular-weight substances that are capable of varying the supramolecular organization of a polymer. 相似文献
9.
《Journal of membrane science》1997,127(2):185-202
Three different types of blend membranes based on chitosan and polyacrylic acid were prepared from homogeneous polymer solution and their performance on the pervaporation separation of water-ethanol mixtures was investigated. It was found that all membranes are highly water-selective. The temperature dependence of membrane permselectivity for the feed solutions of higher water content (>30 wt%) was unusual in that both permeability and separation factor increased with increase in temperature. This phenomenon might be explained from the aspect of activation energy and suggested that the sorption contribution to activation energy of permeation should not always be ignored when strong interaction occurs in the pervaporation membrane system.A comparison of pervaporation performance between composite and homogeneous membranes was also studied. Typical pervaporation results at 30°C for a 95 wt% ethanol aqueous solution were: for the homogeneous membrane, permeation flux = 33 g/m2 h, separation factor = 2216; and for the composite membrane, permeation flux = 132 g/m2 h, separation factor = 1008. A transport model consisting of dense layer and porous substrate in series was developed to describe the effect of porous substrate on pervaporation performance. 相似文献
10.
《Journal of membrane science》1999,160(1):17-30
Chitosan composite membranes having a microporous polysulfone substrate were prepared and tested for the pervaporation dehydration of aqueous isopropanol mixtures. When the composite membrane experienced excessive swelling at the feed mixture of high water content, the composite membranes were found to be segregated in structure due to the opposite characteristics to water of chitosan and polysulfone. Efforts to enhance the structural stability under various pervaporation operational conditions were made. The polysulfone substrate was immersed into hydrophilic binding polymer solutions such as polyvinyl alcohol, polyacrylic acid, and hydroxyethylcellulose before the casting of chitosan layer to increase the affinity between the thin chitosan layer and porous polysulfone layer which resulted in increased geometrical stability of the chitosan/polysulfone composite membranes. The chitosan layer was crosslinked with glutaraldehyde and H2SO4 in acetone solution to control the permselectivity. 相似文献
11.
《Journal of membrane science》1999,154(2):155-162
The membranes in direct methanol fuel cells must both conduct protons and serve as a barrier for methanol. Nafion, the most common fuel cell membrane, is an excellent conductor but a poor barrier. Polyvinyl alcohol pervaporation membranes are good methanol barriers but poor conductors. These and most other pervaporation membranes offer no significant advantages over Nafion in methanol fuel cell applications. However, polybenzimidazole membranes have demonstrated characteristics that suggest up to a 15-fold improvement in direct methanol fuel cells. This improvement may be due to an alternate form of proton conduction in which protons travel via a Grotthus or “hopping” mechanism. 相似文献
12.
Shu-Hsien Huang Chao-Jen Hsu Der-Jang Liaw Chien-Chieh Hu Kueir-Rarn Lee Juin-Yih Lai 《Journal of membrane science》2008
Effect of chemical structures of amines on the performance of isopropanol dehydration by pervaporation through the polyamide thin-film composite membranes prepared by various amines reacting with TMC on the surfaces of the modified asymmetric polyacrylonitrile (mPAN) membranes was investigated. ATR-FTIR, SEM, AFM and water contact angle were used to characterize the chemical structures, morphologies and hydrophilicity of the polyamide active layers of the composite membranes. To investigate the correlation between the free volume of polyamide active layer and pervaporation performance, the free volume variation of the polyamide active layers was probed by positron annihilation spectroscopy (PAS) experiments performed using the slow positron beam. It was found that the pervaporation performance for separating 90 wt.% aqueous isopropanol solutions at 25 °C decreased in the order of EDA–TMC/mPAN membrane > MPDA–TMC/mPAN membrane > PIP–TMC/mPAN and HDA–TMC/mPAN membranes. The relationship between the performance of isopropanol dehydration and the physicochemical properties of the polyamide layers, that is, the free volume, surface roughness and hydrophilicity seemed very well. 相似文献
13.
Chitosan–poly(vinyl alcohol), CS–PVA, blended membranes were prepared by solution casting of varying proportions of CS and PVA. The blend membranes were then crosslinked interfacially with trimesoyl chloride (TMC)/hexane. The physiochemical properties of the blend membranes were determined using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), tensile test and contact angle measurements. Results from ATR-FTIR show that TMC has crosslinked the blend membranes successfully, and results of XRD and DSC show a corresponding decrease in crystallinity and increase in melting point, respectively. The crosslinked CS–PVA blend membranes also show improved mechanical strength but lower flexibility in tensile testing as compared to uncrosslinked membranes. Contact angle results show that crosslinking has decreased the surface hydrophilicity of the blend membranes. The blend membrane properties, including contact angle, melting point and tensile strength, change with a variation in the blending ratio. They appear to reach a maximum when the CS content is at 75 wt%. In general, the crosslinked blend membranes show excellent stability during the pervaporation (PV) dehydration of ethylene glycol–water mixtures (10–90 wt% EG) at different temperatures (25–70 °C). At 70 °C, for 90 wt% EG in the feed mixture, the crosslinked blend membrane with 75 wt% CS shows the highest total flux of 0.46 kg/(m2 h) and best selectivity of 986. The blending ratio of 75 wt% CS is recommended as the optimized ratio in the preparation of CS–PVA blend membranes for pervaporation dehydration of ethylene glycol. 相似文献
14.
A facile route for fabricating novel polyelectrolyte complex membrane with high pervaporation performance in isopropanol dehydration 总被引:1,自引:1,他引:0
Qiang Zhao Jin-Wen Qian Quan-Fu An Qian Yang Peng Zhang 《Journal of membrane science》2008,320(1-2):8-12
Polyelectrolyte complexes (PECs) of sodium carboxymethyl cellulose (CMCNa) and poly(diallyldimethylammonium chloride) (PDDA) were prepared in dilute hydrochloric acid (HCl) aqueous solution and obtained in its solid form. Element analysis and FT-IR showed that the composition of PECs could effectively be tuned by the concentration of HCl in parent polyelectrolyte solution. The PECs were then dissolved in 0.1 mol/L aqueous NaOH and subsequently cast onto polysulfone ultra-filtration membrane. This composite membrane, which has a unique homogeneous PECs separation layer, was subjected to pervaporation test for the first time and gave a performance of J = 3.0 kg/m2 h, α = 960 for 10 wt% water–isopropanol feed at 75 °C. Meanwhile, performance of the PECs membrane displays good stability and unique dependence on feed temperature. These findings, together with its ultra-high performance, are primarily explained by the structure characteristic of PECs. 相似文献
15.
Two negatively charged polyelectrolyte complex colloidal nanoparticles (PEC−) and one positively charged nanoparticle (PEC+) were prepared and used as novel layer-by-layer (LbL) building blocks. These PEC nanoparticles include poly(2-methacryloyloxy ethyl trimethylammonium chloride)/sodium carboxymethyl cellulose (PDMC/CMCNa PEC−), poly(diallyldimethylammonium chloride)/CMCNa (PDDA/CMCNa PEC−) and PDDA/poly(sodium-p-styrenesulfonate) (PDDA/PSS PEC+). LbL multilayer films based on (PEC+/PEC−) were constructed on both quartz slides and modified polyamide (MPA) reverse osmosis support membranes. UV–vis spectroscopy, quartz crystal microbalance (QCM), field emission scanning microscopy (FESEM) and atomic force microscopy (AFM) were utilized to follow the thickness growth and morphology evolution of these multilayer films with increasing bi-layer numbers. LbL multilayer films deposited on MPA support membranes were subjected to pervaporation dehydration of 10 wt% water–isopropanol and effect of bi-layer numbers and feed temperature on pervaporation performance was studied. Generally, PEC+/PEC− can be LbL self-assembled successfully on both substrates with a thickness growth rate ca. 200 nm/bi-layer. Moreover, PEC+/PEC− multilayer films show high pervaporation performance with film thickness up to several micrometers. For example, performance of the multilayer films in dehydrating 10 wt% water–isopropanol at 50 °C is J = 1.18 kg/m2 h, α = 1013 for (PEC+/PDMC-CMCNa PEC−)24 and J = 1.36 kg/m2 h, α = 938 for (PEC+/PDMC-CMCNa PEC−)25, respectively. 相似文献
16.
Qiang Zhao Jinwen Qian Quanfu An Meihua Zhu Minjie Yin Zhiwei Sun 《Journal of membrane science》2009,343(1-2):53-61
Poly(vinyl alcohol) (PVA) was blended with soluble polyelectrolyte complex (PEC) made from poly(diallyldimethylammonium chloride) (PDDA) and sodium carboxymethyl cellulose (CMCNa). Crystallinity, thermal transition, and thermal stability of the PVA/PEC blends were characterized by using wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermal gravity analysis (TGA), respectively. Surface morphology, cross-section and phase structure of the blend membranes were examined by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Surface hydrophilicity and swelling behavior of the blend membranes were examined by water contact angle (CA) and swelling tests. Blend membranes were subjected to isopropanol dehydration, and effects of blend composition, feed composition and feed temperature on pervaporation performance are discussed in terms of phase structures of blend membranes. A performance of J = 1.35 kg/m2 h, α = 1002, was obtained for blend membrane containing 50 wt% PEC in dehydrating 10 wt% water–isopropanol at 70 °C. 相似文献
17.
《Journal of membrane science》1999,157(1):63-71
We investigated the efficiency of pervaporation separation of methanol/methyl-t-butyl ether (MTBE) mixture through chitosan composite membrane modified with sulfuric acid and four surfactants. Effects of feed concentration, temperature, crosslinking degree and type of surfactants were studied. The chitosan composite membrane modified with sulfuric acid showed the pervaporation performance of over 70 wt% methanol in the permeate and flux of 100 g/m2 h measured at 25°C. At 50°C, the separation factor decreased while the flux increased exceeding 300 g/m2 h. For the membrane complexed with surfactants, the permeate showed 98.3 wt% methanol concentration and 470 g/m2 h of permeate flux at 25°C. With increasing operating temperature, the permeate flux remarkably increased to 1170 g/m2 h and the permeate showed 97.8 wt% methanol concentrations. 相似文献
18.
《Journal of membrane science》1997,123(1):35-46
In this work, the pervaporation performance and mechanism of water-ethanol mixtures through symmetric and asymmetric TPX [poly(4-methyl-1-pentene)] membranes were investigated. The results show that TPX is a highly water permselective material although it is strongly hydrophobic. It was found that, for a symmetric dense TPX membrane, the feed solution vaporizes first and then permeates through the membrane. The water selectivity stems from the huge difference in diffusivity between water and ethanol vapors. To improve the permeation flux, asymmetric TPX membranes were prepared by a wet inversion method. However, due to the swelling effect of ethanol on TPX, small pores occur when the dense skin contacts the feed solution, resulting in a loss of water selectivity. Stain experiments were carried out to verify this mechanism. In addition, it was found that a parallel model can describe the mechanism quite accurately. Good agreement between the theoretical calculation and experimental measurement has been obtained. Furthermore, we also found that the loss of selectivity can be avoided by turning the asymmetric membrane over; that is, let the dense skin face the permeate. 相似文献
19.
Wei Xin Yunjun LuoXuejing Song Jingru LiuYin Yang Yong LvYongbin Jiu 《Journal of membrane science》2008
Pervaporation membranes containing hyperbranched polymer were prepared from the blends of ethyl cellulose (EC) and hyperbranched polyester (HBPE). The FT-IR analysis indicated that the interactions between EC and HBPE decreased as increasing the generation of HBPE. The membrane containing HBPE (EC-HBPE) showed both higher sorption ratio and selectivity than pure EC membrane. The effects of HBPE content as well as temperature of feed solutions on the membrane performance were investigated in detail. The EC-HBPE membrane exhibited much higher permeate flux than the EC membrane, while the separation factor maintained at same level. 相似文献
20.
《Journal of membrane science》1999,154(2):221-228
Using glycidyl methacrylate (GMA) as a grafting monomer and a porous high density polyethylene film as a substrate, plasma-graft polymerized membranes were prepared by the different plasma treatment manners, namely, homogeneous both-side (HBS) and one side (OS) treatments. The poly(GMA)-grafted membranes displayed two different types of the feed composition dependence of permeation flux and separation factor for pervaporation (PV) of benzene/cyclohexane (Bz/Cx) mixtures, depending on the plasma treatment manner and the graft yield. The membranes prepared by the HBS treatment and under mild polymerization conditions displayed the highest performance with a permeation flux of 0.30–0.37 kg/m2 h and a separation factor of 19–22 at feed Bz of 60 wt% and 70°C. The membranes exhibited high performance with excellent durability for PV of other aromatic/aliphatic hydrocarbon mixtures. 相似文献