Separation of alcohol–water mixture by pervaporation through a novel natural polymer blend membrane–chitosan/silk fibroin blend membrane

A novel natural polymer blend membrane, namely chitosan/silk fibroin blend membrane, was prepared. The selective solubility and the pervaporation properties of alcohol–water mixture were studied. The results showed that the membrane was water selective and the separation factor of ethanol–water mixture could be improved compared to pure chitosan membrane, when silk fibroin content in blend membrane was no more than 40 wt %. The blend membrane exhibited a best performance, (i.e., the water in permeate was large than 99 wt % when silk content was 20 wt % and the crosslinking agent–glutaraldehyde content was 0.5 mol %). The mechanism of improvement on pervaporation properties was explained by reducing the free volume and freeing hydrophilic groups of chitosan because of the strong intermolecular hydrogen bond forming between chitosan and silk fibroin in blend membrane. In addition, the influence of operation temperature and feed concentration as well as the pervaporation properties of isopropanol–water mixture were also studied. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 975–980, 1999     

Separation of phenol–water mixture by membrane pervaporation using polyimide membranes

Separation of components of aqueous waste streams containing organic pollutants is not only industrially very important but also is a challenging process. In this study, separation of a phenol–water mixture was carried out by using a membrane pervaporation technique with indigenously developed polyimide membranes. The membranes were found to permeate water selectively. The total flux as well as that of the individual components were measured. The effect of lithium chloride modification of polyimide film on total flux was investigated. The total flux obtained with 2% lithium chloride modification was about 3.6 times higher than that obtained with virgin membrane. The effects of different parameters such as feed composition and temperature on flux, and separation factor were determined. With modified membrane, a separation factor as high as 18.0 was obtained for water at 27°C and with 8.0 wt % phenol solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 822–829, 2002     

Preparation of crosslinked alginate composite membrane for dehydration of ethanol–water mixtures

The purpose of this article was to develop new membranes with a high selectivity and permeation rate for separation of an alcohol/water system. Crosslinked alginate composite membranes were prepared by casting an aqueous solution of alginate and 1,6‐hexanediamine (HDM) onto a hydrolyzed microporous polyacrylonitrile (PAN) membrane. The influence of hydrolysis of the support membrane and crosslinking agent content in a dense layer on the selectivity and flux was studied and it was shown that both could improve the separation performance of the composite membrane greatly. The countercation of alginate coatings as a dense separating layer also influenced the separation properties of the membrane, which was better for K⁺ than for Na⁺. This novel composite membrane with K⁺ as a counterion has a high separation factor of 891 and a good permeation rate of 591 g m⁻² h⁻¹ for pervaporation of a 90 wt % ethanol aqueous solution at 70°C. At the same time, SEM micrographs showed that the pore structure of the PAN microporous membrane is changed by hydrolysis. The reason for the influence of the preparation conditions on the separation performance of the novel membrane is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3054–3061, 2000     

Preferential separation of ethanol from aqueous solution through hydrophilic polymer membranes

The pervaporation behaviors of aqueous ethanol mixtures through the poly(ethylene oxide) (PEO)/chitosan (CS) blend membrane were investigated. The results show that both CS and PEO/CS membrane preferentially permeate ethanol at a lower alcohol concentration in feed, and the selectivity of CS membrane toward alcohol can be greatly improved by introducing hydrophilic polymer PEO into CS. The PEO/CS blend membrane gave a separation factor of 4.4 and a flux of 0.9 kg m⁻² h for 8 wt % of ethanol in the feed at 20°C. At the same time, the reason introducing PEO can improve alcohol-permselectivity of CS membrane is explained on the basis of experimental data. Blending with PEO made the structure of CS chain looser, which resulted in ethanol molecules passing through easily, on the other hand, strengthened the ability of forming water clusters that inhibit the permeation of water molecules. From the experimental results, although the PEO/CS blend membrane was not a usable membrane with high selectivity to alcohol, a new method to prepare alcohol-permselective membranes appears to be developed by modifying hydrophilic polymers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1145–1151, 1999     

Swelling behavior of pervaporation membranes in ethanol–water mixtures

Novel hydrophobic composite membranes made of crosslinked poly(dimethylsiloxane) and poly(methyl hydrogen siloxane) (PDMS–PMHS) with various amounts of catalyst were prepared. Pervaporation experiments with water–ethanol mixtures revealed that an optimum ratio of catalyst to polymer base existed. Both swelling behavior and dynamic–mechanical properties of these silicone films were studied. The swelling experiments in different mixtures of ethanol and water determined that ethanol is preferentially sorbed and that the membranes are only capable to absorb a limited quantity of solvent. Equilibrium swelling data were also used in combination with the analysis of the viscoelastic relaxation of the swollen samples to obtain the dependence of the dynamic–mechanical properties of the silicone films on the quantity of permeants sorbed into the membrane. It was observed that the permselective parameters were related with the mobility of the chains and the free volume. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1424–1433, 2000     

Separation of alcohol–water mixture by pervaporation through a reinforced polyvinylpyridine membrane

A membrane consisted of cross-linked poly(4-vinylpyridine) and reinforced by a nonwoven cloth made of poly(ethylene terephthalate) was prepared by copolymerization of 4-vinylpyridine with divinylbenzene in the presence of the nonwoven cloth. Pervaporation performance of this polyvinylpyridine membrane was examined at several feed alcohol concentrations and temperatures. The membrane showed water selectivity, and the permselectivity, α_W/_A, for the alcohol–water mixture was in the order isopropyl > propyl > tert-butyl > ethyl > methyl. The membrane showed a large permeability, and the pervaporation flux, ?, for the ethanol–water mixture was 7–13 kg/h per square meter of the membrane in pervaporation with sweeping of carbon dioxide under atmospheric pressure and at 40°C. The membrane was durable and long lasting for a prolonged-period, and permselectivity and permeability of the membrane did not fall off even after repeated use for 1000 h. © 1993 John Wiley & Sons, Inc.     

Novel sodium alginate/polyethyleneimine polyion complex membranes for pervaporation dehydration at the azeotropic composition of various alcohols

Dense polyion complex membranes of anionic sodium alginate (NaAlg) and cationic polyethyleneimine (PEI) were prepareand crosslinked with glutaraldehyde for dehydration of alcohol–water mixtures by pervaporation (PV). The membranes were characterized by ion‐exchange capacity measurement, Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy to investigate the extent of cross‐linking, intermolecular interactions, thermal stability, and surface and cross‐sectional morphologies, respectively. Wide‐angle X‐ray diffraction was used to investigate the crystallinity of the membranes. PV dehydration characteristics of the membranes were determined as a function of PEI content, crosslinking time as well as feed water composition. Transport parameters such as sorption, diffusion and permeability of water and alcohols through the membranes were determined. Among the four different membrane compositions, the polyion complex containing 40% PEI was found to yield optimum separation data in terms of membrane stability, selectivity and permeability. On the other hand, 10% PEI‐containing membrane gave the highest selectivity with the lowest flux at ambient temperature, but the membranes were not sufficiently stable. Copyright © 2007 Society of Chemical Industry     

Water–alcohol separation by pervaporation through poly(amide-sulfonamide)s (PASAs) membranes

Pervaporation membranes derived from seven homopolymers of poly(amide-sulfonamide)s (PASAs) were prepared by casting 10–17% polymer solutions of N,N-dimethylacetamide. The membranes were characterized by sorption experiments, scanning electron microscope, and wide-angle X-ray diffraction. During the pervaporation of 90 wt % aqueous solution of methanol, ethanol, 1-propanol, and 2-propanol, all membranes were preferentially permeable to water, and their separation factors were mainly dependent on the molecular weight of the solvent. The exact structure of the PASAs had a profound effect on their pervaporation characteristics. Polymeric membrane based on N,N′-bis(4-aminophenylsulfonyl)-1,3-diaminopropane and isophthaloyl chloride exhibited the best selectivity factor of 1984 for a 10 : 90 (by weight) mixture of water/ethanol at 20°C. However, the permeation rates of all materials for dehydration of 90 wt % ethanol were slow in a range of 6.6–34.4 g m⁻² h⁻¹. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1113–1119, 1997     

Improvement of properties of silica‐filled styrene–butadiene rubber compounds using acrylonitrile–butadiene rubber

Since silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica‐filled styrene–butadiene rubber (SBR) compounds was studied using acrylonitrile–butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica‐filled SBR compounds were compared with the carbon black‐filled compounds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1127–1133, 2001     

Permeate pressure build-up in shellside-fed hollow fiber pervaporation membranes

Pervaporation of water, ethanol and isopropanol through polydimethylsiloxane hollow fiber membranes was studied, with emphasis on elucidating the significance of permeate pressure build-up inside the fibers when the shell-feed mode of operation was used. The differential form of the Hagen-Poiseuille equation was used to describe the permeate pressure profile, and the theoretical predictions of permeate productivity were confirmed by experimental data. A parametric analysis showed that the dimensions of the hollow fiber (inside and outside diameters, and length) significantly affected the overall pervaporation performance of a hollow fiber membrane module, and the fiber dimensions must be optimized in order to achieve high productivity.     

Removal of pyridine from water by pervaporation using filled SBR Membranes

Styrene butadiene rubber (SBR) was efficiently cured (crosslinked) by using sulfur to accelerator ratio less than unity. This cured SBR was further compounded with carbon black filler (grade N330) with three different doses i.e., 5, 10, and 20 wt % of filler to form three different filled and crosslinked membranes, i.e., SBR5, SBR10, and SBR20. These filled rubber membranes and one unfilled but efficiently cured membrane, i.e. SBR0, were used for pervaporative removal of pyridine from its mixtures with water. The filled membranes were found to show better selectivity and mechanical properties but lower flux than the unfilled membrane. All of these membranes showed reasonably good range of flux and pyridine selectivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Acrylonitrile‐based copolymer membranes for the separation of methanol from a methanol–toluene mixture through pervaporation

The membrane selection criteria for the preferential permeation of a particular component were examined for the pervaporative separation of methanol from a mixture of methanol and toluene. One polyacrylonitrile homopolymer and five different copolymer membranes (i.e., acrylonitrile with maleic anhydride, acrylic acid, methacrylic acid, methyl methacrylate, and styrene) were prepared through emulsion polymerization. All these monomers were selected on the basis of the solubility parameter concept. The second monomer had an influence on the permselectivity and flux, and this effect was investigated. The structures of the copolymers, the features of their sorption layers, and their permeation paths were examined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 243–252, 2005     

Ethanol/water mixture pervaporation performance of b‐oriented silicalite‐1 membranes made by gel‐free secondary growth

b‐oriented silicalite‐1 membranes on porous silica supports were synthesized using gel‐free secondary growth. The porous silica supports were made by pressing crushed quartz fibers followed by sintering and polishing, and further modified by slip‐coating three layers of Stöber silica particles (1000, 350, and 50 nm). The b‐oriented seed layers were prepared by rubbing silicalite‐1 particles (2 μm × 0.8 μm × 3 μm along a‐, b‐, and c‐axis, respectively) after depositing a polymeric layer on the support. After silicalite‐1 seed deposition, a final coating of spherical silica particles was applied. Well‐intergrown, μm‐thick, b‐oriented membranes were obtained, which, after calcination, exhibited ethanol permselectivity in ethanol/water mixture pervaporation. At 60°C and for ～5 wt % ethanol/water mixtures, the best membrane exhibited overall pervaporation separation factor of 85 (corresponding to membrane intrinsic selectivity of 7.7) and total flux of 2.1 kg/(m²·h). This performance is comparable to the best performing MFI membranes reported in the literature. © 2015 American Institute of Chemical Engineers AIChE J, 62: 556–563, 2016     

Reliable production of highly concentrated bioethanol by a conjunction of pervaporation using a silicone rubber sheet‐covered silicalite membrane with adsorption process

For the production of highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, pervaporation performance was investigated using a silicalite membrane entirely covered with a silicone rubber sheet to prevent direct contact with acidic compounds. By using a resistance model for membrane permeation, the separation factor of the covered silicalite membrane towards ethanol can be estimated from the individual pervaporation performances of the silicalite membrane and the silicone rubber sheet. No decrease in the ethanol concentration through the silicone rubber sheet‐covered membrane was caused when ethanol solutions containing succinic acid were supplied. By directly passing the permeate‐enriched ethanol vapor mixed with water vapor through a dehydration column packed with a molecular sieve of pore size 0.3 nm, highly concentrated bioethanol up to 97% (w/w), greater than the azeotropic point in the ethanol/water binary systems, can be obtained from 9% (w/w) fermentation broth. Copyright © 2004 Society of Chemical Industry     

Separation of aqueous phenol through polyurethane membranes by pervaporation

The separation of a phenol-water mixture using a polyurethane membrane by a pervaporation method was investigated. Polyurethane was selected as a membrane material because its affinity for phenol was considered to be high. Polyurethane was prepared by the polyaddition of 1,6-diisocyanatohexane and polytetramethyleneglycol. The polyurethane layer was sandwiched with a porous polypropylene membrane (Celgard® 2500). Pervaporation measurement was carried out under vacuum on the permeate side, and the permeate vapor was collected with a liquid nitrogen trap. The phenol concentration in the permeate solution increased from 0 to 65 wt % with increasing feed concentration of phenol from 0 to 7 wt %. The total flux also increased up to 930 g m^-2 h^-1 with increasing phenol partial flux. In the sorption measurement at 60°C, the concentration of phenol in the membrane was 68 wt %, which was higher than that of the permeate solution. Therefore, it was considered that the phenol selectivity was based on high solubility in the polyurethane membranes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:469–479, 1997     

Natural rubber/poly(acrylic acid) semi‐interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures

Pervaporation membranes for the dehydration of water–ethanol mixtures were prepared from a semi‐interpenetrating polymer network (semi‐IPN) of natural rubber (NR) and crosslinked poly(acrylic acid) (PAA). The swelling studies revealed that hydrophilic PAA present in the semi‐IPN membranes caused the membranes to swell greatly in water. The swelling degree of the membranes in water was significantly affected by the amount ratio between the hydrophobic NR and the hydrophilic PAA. The sorption experiments of the NR/PAA membranes in various concentrations of water–ethanol mixtures suggested the preferential sorption to water. However, for the membrane with high PAA content, the water sorption selectivity decreased considerably at high water concentration of water–ethanol mixtures because the membrane was in the highly swollen state. Pervaporation separations of water–ethanol mixtures using NR/PAA membranes were performed and it was found that at low water concentrations of feed mixtures, increasing the PAA content of the membrane can enhance both water permeation flux and selectivity. Additionally, under low feed water concentration, increasing the feed temperature would increase the water flux with the decreasing of the ethanol flux. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A型分子筛膜在分离乙二醇水溶液中的应用

采用抽空涂晶二次生长法成功地合成出了A型分子筛膜,研究了乙二醇水溶液在A型分子筛膜上的渗透气化和蒸气渗透分离性能,考察了温度、浓度对渗透通量的影响,完成了1000 h的稳定性实验。结果表明,A型分子筛膜对EG水溶液具有非常高的分离选择性和稳定性,分离系数达到10000,在120 ℃透量达到10 kg/(m2•h)。     

Separation of alkane–acetone mixtures using styrene–butadiene rubber/natural rubber blend membranes

Conventionally vulcanized styrene–butadiene rubber/natural rubber blend membranes were prepared for the pervaporation separation of alkane–acetone mixtures. Swelling measurements were carried out in both acetone and n‐alkanes to investigate the swelling behavior of the membranes. The swelling behavior was found to depend on the composition of the blend. The effects of blend ratio, feed composition, and penetrant size on the pervaporation process were analyzed. The permeation properties have been explained on the basis of interaction between the membrane and solvents and blend morphology. The SBR/NR 70/30 blend membrane showed higher selectivity among all the membranes used. Flux increases with increasing alkane content in the feed composition. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3059–3068, 1999     

Pervaporation separation of water/alcohol mixtures through hydroxypropylated chitosan membranes

The present study investigated the pervaporation performance of novel hydroxypropylated chitosan (HPCS) membranes to separate water from an aqueous alcohol solution. Hydroxypropylated chitosan was prepared from the reaction of chitosan and propylene oxide. The results show that the separation factor decreases and the flux increases with increasing of the substitution degree of the hydroxypropylated chitosan membrane. Crosslinking with glutaraldehyde or treatment with Cu²⁺ can improve the pervaporation performance of modified chitosan membrane grately. The performance data indicate that the crosslinking hydroxypropylated chitosan membrane treated with Cu²⁺ is an excellent pervaporation membrane for the separation of alcohol–water mixtures, and one-stage separation is attainable for some alcohol–water mixtures such as an n-propanol–water and an isopropanol–water system, which has a good separation factor of 220 for the n-PrOH/water system and 240 for the i-PrOH/water system using 85 wt % alcohol concentration at 60°C. The flux for both cases is around 0.5 kg m⁻² h⁻¹. At the same time, the structure of the chemically modified chitosan membranes and their separation characteristics for aqueous alcohol solutions are also discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2035–2041, 1998     

Three‐component mixed matrix organic/inorganic hybrid membranes for pervaporation separation of ethanol–water mixture

Mixed matrix membranes (MMMs) were made by incorporating vinyltrimethoxysilane (VTMS)‐modified Silicalite‐1 zeolite nanoparticles (V‐Silicalite‐1 NPs) into fluorinated polybenzoxazine (F‐PBZ) modified polydimethylsiloxane (PDMS) polymer through in situ polymerization method. The membrane morphology, surface wettability, and pervaporation performance were systematically investigated. The addition of F‐PBZ into PDMS membranes resulted in substantially improved flux and marginal increase of separation factor, which is the result of higher free volume and higher hydrophobicity caused by the addition of F‐PBZ. The modification of Silicalite‐1 NPs improved the interfacial contact between zeolite crystals and polymer phase. The incorporation of hydrophobic V‐Silicalite‐1 zeolite NPs into the PDMS membranes led to much higher separation factor but reduced flux, which is the result of increased hydrophobicity and reduced free volume. The three‐component MMMs with V‐Silicalite‐1 zeolite NPs in the F‐PBZ fluorinated PDMS exhibited separation factor of 28.7 and flux of 0.207 kg m^?2 h^?1 for 5 wt % ethanol aqueous solution at 50 °C, while the pure PDMS membranes only had separation factor of 4.8 and flux of 0.088 kg m^?2 h^?1. The substantial increase of both flux and separation factor were attributed to the higher hydrophobicity and free volume caused by the incorporation of both hydrophobic zeolite crystals and F‐PBZ polymer into the PDMS membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44753.