Separation of water–ethanol by pervaporation through polyion complex composite membrane

For the purpose of separating alcohol–water mixtures by the use of the pervaporation technique, new composite membranes composed of polyion complexes (PIC) as a separating layer were developed. The polyion complex structure, consisting of polyacrylic acid (PAA) and polycation, provided excellent permeation rate and selectivity. Among the polycations, ionenes, which have quaternary ammonium groups in the backbone chain, were effective in giving membranes of higher permselectivities. High selectivity of PIC membranes was observed at high ethanol concentration regions in the feed mixture. For the azeotropic mixture of water/ethanol (95 wt % EtOH) at 60°C, the PAA-based PIC membrane had the following separation properties: separation factor ～ 3,500 and permeation rate ～ 1.6 kg/m² h.     

Development of polyion complex membranes for the separation of water–alcohol mixtures. I. Synthesis and physical properties of the polycations based on 1,3-di (4-pyridyl) propane

To prepare good polymeric materials for the preparation of the polyion complex membranes useful for water–alcohol separation, polycations were synthesized by the quaternization polymerization of 1,3-di(4-pyridyl)propane with dibromoalkanes or with 1,8-bis (p-toluenesulfonyl)octane. The polycations were characterized by FTIR spectroscopy, viscometry, DSC, and X-ray diffractometry. The polycations were in molecular weight ranges good enough to be used as membrane materials. The polycations were very hygroscopic and easily soluble in highly polar solvents such as water and these properties might be good for the membrane materials. The thermal properties and X-ray diffraction patterns of these polycations suggested that the polycations were semicrystalline and difficult to form crystals by melt crystallization. © 1994 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     

Performance evaluation of sodium alginate–Pebax polyion complex membranes for application in direct methanol fuel cells

A novel polyion complex membrane was synthesized for direct methanol fuel cell application through the blending of the natural biopolymer sodium alginate (SA) with the synthetic polymer Pebax [poly(ether‐block ‐amide)]. The blend was covalently crosslinked with glutaraldehyde (GA) and sulfonated with sulfuric acid (H₂SO₄), after which characterization by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffractometry, thermogravimetric analysis, and universal testing machine techniques was carried out. The SA–Pebax–GA–H₂SO₄ membrane exhibited a high ion‐exchange capacity of 2.1 mequiv/g, an optimum water sorption of 17.3%, and a low methanol sorption of 9.5%. A desirably low methanol permeability of 9.25 × 10^?8 cm²/s and a high proton conductivity of 0.067 S/cm were obtained as against corresponding values of 1.82 × 10^?6 cm²/s and 0.077 S/cm reported for a commercial Nafion 117 membrane. Moreover, a high selectivity of 6.5 × 10⁵ Ss/cm³ with a power density of 0.17 W/cm² was achieved with the indigenous blend membrane at a potential of 0.34 V. Molecular dynamics simulation was performed along with the estimation of fractional free volume to explain the transport behavior of water and methanol molecules through the membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44485.     

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     

Pervaporation separation of water–isopropyl alcohol mixture by PVA/LiBr membrane

Hydrophilic polyvinyl alcohol membranes, modified by lithium bromide, were prepared with glutaraldehyde as a crosslinking reagent. The membranes were investigated for the pervaporation dehydration of a water–isopropyl systems. The effect of the feed temperature on permeation flux and membrane selectivity was studied. The characterization of modified membranes was performed using Fourier transform infrared spectroscopy (FT‐IR), differential scanning calorimeter (DSC) and X‐ray diffraction. It was observed that the crystallinity of membranes increased as lithium bromide was added to the polymer. High performance liquid chromatography (HPLC) was used to analyze water content and isopropyl alcohol in the feed and permeate samples The pervaporation tests also confirmed an enhancement in water permeability through adding LiBr to the polymer, because of the high hydrophilic properties of this salt. According to pervaporation experiments conducted at 50°C, the water flux increased from 0.1049 kg/ m² hr to 0.1114 kg/ m² hr as 0.5 wt% of LiBr was added to the polymer matrix. Furthermore, an addition of 1 wt% of LiBr compared to homogeneous PVA membrane increased selectivity from 76 to 779. POLYM. ENG. SCI., 59:E101–E111, 2019. © 2018 Society of Plastics Engineers     

Effect of sorbed water on dielectric and mechanical properties of polyion complex

Effect of sorbed water on dielectric and mechanical properties is studied for three kinds of polyion complex (PIC) membranes formed from equal moles of polyanion [poly(sodium 4-vinylbenze-sulfonate)] and three polycations of different structural isomerisms [poly(4-vinylphenethyltriethylammonium bromide), poly(3-vinylphenethyltriethylammonium bromide), and random copolymer of these monomers]. Sorption isotherms and swelling characteristics indicate that PIC of parapolycation includes more water microphases than PIC of meta-polycatio. Complex dielectric constants of three PICs with varied water contents are measured at frequencies from 10 Hz to 100 kHz and the relaxation is analyzed in terms of the heterogeneous structure. Stress–elongation relationships of PICs equilibrated with water and aqueous NaBr indicate that yield and break stresses are higher for PIC of meta-polycation than that of para-polycation and decrease with increasing NaBr concentration above 0.1M.     

Pervaporation separation of binary organic–aqueous liquid mixtures using crosslinked PVA membranes. III. Ethanol–water mixtures

The application of the pervaporation process in biotechnology is rapidly growing. A two stage pervaporation process could be applied to the downstream processing of ethanol fermentation. In this paper, the second stage process—a water-selective process—was investigated in detail using the crosslinked poly(vinyl alcohol) membranes with the low molecular weight of poly(acrylic acid) as the crosslinking agent. The ratio of poly(vinyl alcohol) and poly(acrylic acid) in the membrane was 90/10, 85/15, and 80/20 by weight. The prepared membranes were tested to separate the various compositions of the water–ethanol mixtures, specially 50/50 solution at 60°C and 30/70, 20/80, 10/90, and 4.4/95.6 solutions at 60, 70, and 75°C. For water: ethanol = 50 : 50 solution, the separation factor α_w/e = 260 at 75°C was obtained by using a PVA/PAA = 80/20 membrane. The permeation rate and the separation factor at the azeotropic point of a water–ethanol mixture showed 30 g/m²/h and 5800 at 75°C, respectively, when a PVA/PAA = 80/20 membranes was used. © 1995 John Wiley & Sons, Inc.     

Poly(ether sulfone) supported hybrid poly(vinyl alcohol)–maleic acid–silicone dioxide membranes for the pervaporation separation of ethanol–water mixtures

Microporous poly(ether sulfone) (PES) supported hybrid polymer–inorganic membranes were prepared by the crosslinking of poly(vinyl alcohol) (PVA), maleic acid (MA), and SiO₂ via an aqueous sol–gel route and a solution‐casting method. The membrane performance was tested for the pervaporation separation of ethanol–water mixtures from 20 to 60 °C with a feed ethanol concentration of 96 wt %. The membrane characterization results reveal that different SiO₂ loadings affected the crystallinity and roughness of the membranes. The PVA–MA–SiO₂ membrane containing 10 wt % SiO₂ showed that SiO₂ nanoparticles were well dispersed within the polymer matrix; this resulted in significant enhancements in both the flux and selectivity. The membrane achieved a high water permeability of 1202 g·μm·m^?2 h^?1 kPa^?1 and a selectivity of 1027 for the separation of a 96 wt % ethanol‐containing aqueous solution. This enhanced membrane performance might have been due to the dense crosslinking membrane network, increased free volume, and uniform distribution of SiO₂ nanoparticles. Both the water and ethanol fluxes increased with the feed water concentration and temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44839.     

Pervaporation separation of water‐isopropanol mixtures using polymeric membranes: Modeling and simulation aspects

Pervaporation technique was used to separate water + isopropanol azeotropic mixtures at 30°C using pure sodium alginate, pure poly(vinyl alcohol), and blend membranes of sodium alginate containing 10 and 20 mass % of poly(vinyl alcohol). The membrane performance was studied by calculating flux, selectivity, pervaporation separation index, and enrichment factor. Pure sodium alginate membrane gave the highest pervaporation separation index for all compositions of water. Pervaporation experiments were carried out for 10 mass % containing water + isopropanol mixture at 30, 40, and 50°C. The Arrhenius activation parameters were computed. The PV results have been analyzed by considering complete mixing and plug flow models. Design parameters, like membrane area, permeate concentrations, flux, stage cut, separation selectivity, etc., have been calculated for different feed compositions of water in the mixture. Results are explained in terms of sorption‐diffusion principles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1143–1153, 2005     

Hydrocarbons separation with polymer membranes. I. Butadiene–isobutene separation with nitrile rubber membranes

The permeation characteristics and the selectivity of four nitrile rubber films with respect to 1,3-butadiene and isobutene were studied as a function of experimental conditions and the nature of membrane material. A specific research apparatus was developed, allowing the determination of both permeation rate and selectivity, at a temperature varying between 0° and 30°C and under a pressure of from 1 to 3 bars. The inverse proportion of permeation rate to membrane thickness was verified for a thickness of from 12 to 500 microns. An increase in temperature promotes liquid permeation and is detrimental to gas permeation, the latter being facilitated by an increase in pressure. The introduction of an inert gas pressure on the liquid did not bring about an increase in the liquid permeation rate. The permeation rate decreases as a result of an increase in the proportion of acrylonitrile in the rubber, which also affects selectivity; the latter reaches a maximum value when said proportion is about 23%. The effect of the composition of the feed mixture was also studied and curves were determined relating, simultaneously, selectivity and permeation rate to the 1,3-butadiene content. Selectivity is maximal with mixtures having a very high 1,3-butadiene content. The solubilities of 1,3-butadiene and of isobutene in the four types of nitrile rubber were measured at 0°C and at 20°C (68°F). Selectivity can be interpreted in terms of the solubilities of the two hydrocarbons.     

Pervaporation separation of water–ethanol mixtures using metal‐ion‐exchanged poly(vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) membranes

Poly(vinyl alcohol)/sulfosuccinic acid (PVA/SSA) membranes in the hydrogen form were converted to monovalent metal ion forms Li⁺, Na⁺, and K⁺. The effect of exchange with metal ions was investigated by measuring the swelling of water–ethanol (10/90) mixtures at 30 °C and by the pervaporative dehydration performance test for aqueous ethanol solutions with various ethanol concentrations at 30, 40, and 50 °C. In addition, electron spectroscopy for chemical analysis (ESCA) analysis was carried out to study the quantity of metal ions in membranes. From the ESCA analysis, the lithium ion quantity in the resulting membranes is greater than that of any other metal ions in question because of the easy diffusion of a smaller metal ion into the membrane matrix. The swelling ratio was in the following order: PVA/SSA‐Li⁺ > PVA/SSA‐Na⁺ > PVA/SSA‐K⁺ membranes. For pervaporation, the PVA/SSA‐Na⁺ membrane showed the lowest flux and highest separation factor for all aqueous ethanol solutions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1867–1873, 2002     

Pervaporation separation of a water–ethanol mixture by PSF–PEG membrane

For dehydrating a water–ethanol mixture by pervaporation, a polysulfone–And poly(ethylene glycol)(PSF–PEG) membrane was prepared. The separation performance of water and ethanol was found to strongly depend on the diffusion selectivity of permeates. On the other hand, the solubility selectivity of water to ethanol showed only minor change with an increasing PEG composition of the PSF–PEG membrane. This study found that the PEG content in a PSF–PEG membrane showed mobility enhancement of pervaporation properties and that the diffusion difference of permeates increased with increasing PEG content. The effect of PEG content on separation performance was a result of the improvement of the permeate diffusion properties of the PSF/PEG membrane. The diffusion difference in the membrane, not the solubility of water–ethanol in the membrane, was the dominant factor for the separation. Suitable PEG content in PSF/PEG membranes can prepare a high‐performance pervaporation membrane. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2158–2164, 2003     

Immobilization of catalase by polyion complex

Catalase was immobilized in a polyion complex from poly(sodium 2-acrylamide-2-methyl-1-propanesulfonate) and poly[2-(trimethylammonioethyl) methacrylate chloride]. Polyion complex formation between the two polyions was found to proceed stoichiometrically by the turbidimetric titration. Immobilization of catalase was achieved by conducting the complexation in the presence of the enzyme, which was established to be incorporated in the polyion complex networks. The fixed catalase showed higher thermal stability than the original enzyme. Furthermore, the stability and the activity of the fixed catalase were improved by annexing inert components such as albumin, histone, or lecithin at the time of polyion complex formation.     

Application of ionically crosslinked latex membranes to the separation of ethanol–water mixtures by pervaporation

Ionically crosslinked latex membrane is prepared by treating the latex membrane containing carboxyl groups with salt solutions. Pervaporation separation with these membranes shows that the ionic crosslinking raises the permeability, with the selectivity being maintained or increased. Ionically crosslinked membranes also have a higher pervaporation separation efficiency than the nontreated membranes. Permeability and selectivity increase with increasing ethanol content in feed. The temperature dependence of permeability can be correlated by the Arrhenius relationship. © 1994 John Wiley & Sons, Inc.     

Novel cell sheet carriers using polyion complex gel modified membranes for tissue engineering technology for cell sheet manipulation and transplantation

A novel hydrogel membrane composed of polyion complex gels was developed to transfer cultured cell sheets from thermoresponsive cell culture dishes. Polyion complexes have been prepared by mixing poly(N,N-dimethylacrylamide-co-2-acrylamido-2-methylpropane sulfonic acid) (P(DMAAm-co-AMPS)) as anionic water-soluble polymers and poly(N,N-dimethylacrylamide-co-2-acryloxyethyltrimethylammonium chloride) (P(DMAAm-co-AETA-Cl)) as cationic water-soluble polymers. Various polyion complexes have been prepared by changing the composition of two polyelectrolytes. Through a set of Teflon^® ring device, polyion complexes have been modified on porous membranes by electron beams irradiated cross-linking and covalent grafting technique. NIH/3T3 mouse cells as demo cells have been cultured to prepare cell sheets. This cell sheets could be recovered by using the resulting polyion complex gels as cell sheet carriers from temperature-responsive cell culture surfaces and be transferred to new collagen-coated tissue culture polystyrene dishes. This new technique has potential applications not only for transplantation but for creation of three dimensional layered cell sheet tissues.     

Cellulose–poly(acrylamide–acrylic acid) interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures. II. Effect of ionic group contents and cellulose matrix modification

The separation properties in the dehydration of a water–ethanol mixture and the swelling behavior of interpenetrating polymer network (IPN) pervaporation membranes based on a cellulose or cellulose–hydroxyethyl cellulose (HEC) matrix and poly(acrylamide and/or acrylic acid) were investigated depending on the ionic acrylate groups content (γ) in synthetic polymer chains (0–100 mol %), the HEC content in the matrix (0–50 wt %), and the temperature (25–60°C). The separation factor (α), permeation rate (P), and separation index (αP) significantly improved with increasing γ values only for the separation of concentrated ethanol solutions (～86 wt %). For more dilute solutions of ethanol (～46 wt %), the P and αP values also increased but no considerable increase in α was observed. All types of membranes based on the cellulose matrix were characterized by a drastic decrease in the values of P at [EtOH] ≥90 wt % and, as a result, a decrease in the separation index (kg m^?2 h^?1) from ～2000 (for 86 wt % EtOH, 50°C) to ～240 (for 95 wt % EtOH, 50°C), which correlates with a decrease in the degree of membrane swelling. The modification of the cellulose matrix by introducing HEC into it makes it possible to increase considerably the membrane swelling in concentrated EtOH solutions and, hence, the αP value to ～760 (95 wt % EtOH, 50°C). All types of IPN membranes exhibit a marked increase in both α and P when the temperature increases from 25 to 60°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1452–1460, 2001     

Synthesis and characterization of hybrid membranes using poly(vinyl alcohol) and tetraethylorthosilicate for the pervaporation separation of water–isopropanol mixtures

Hybrid membranes were prepared using poly(vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis and cocondensation reaction for the pervaporation separation of water‐isopropanol mixtures. The resulting membranes were characterized by Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, and differential scanning calorimetry. The glass transition temperature of these membranes varied from 100 to 120°C with increasing TEOS content. Effects of crosslinking density and feed compositions on the pervaporation performances of the membranes were studied. The membrane containing 1.5:1 mass ratio of TEOS to PVA gave the highest separation selectivity of 900 at 30°C for 10 mass % of water in the feed mixture. It was found that the separation selectivity and permeation flux data are strongly dependent on the water composition of the feed and operating temperature. However, the membrane with the highest crosslinking density showed unusual pervaporation properties. The overall activation energy values were calculated using the Arrhenius‐type equation. The activation energy values for the permeation and diffusion varied from 49.18 to 64.96 and 55.13 to 67.31 kJ/mol, respectively. Pervaporation data have also been explained on the basis of thermodynamic quantities. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1304–1315, 2004     

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     

Selective separation of water from water–ethanol solution through quarternized poly(4-vinylpyridine-co-acrylonitrile) membranes by pervaporation technique

Polymer membranes having cationic charge site, poly(1-alkyl-4-vinylpyridinium iodide-co-acrylonitrile) (alkyl: methyl, butyl, or octyl) were prepared in terms of coulombic interaction for separation of water–ethanol mixtures. The incorporation of cationic charge site into the membrane led to improve not only separation factors (selectivity toward water) but also flux number in the separation of aqueous ethanol solution by pervaporation technique. Target values, which were requested to have from the viewpoint of industrial utilization for separation of aqueous ethanol solution were attained as follows: separation factor toward water over 50 and flux value over 500 g m^?2 h^?1, through poly(1-methyl-4-vinylpyridinium iodide-co-acrylonitrile) (membrane 3 ) (quarternized fraction of pyridinium moiety, 89.5%; mol fraction of pyridinium moiety, 0.034) and poly(1-butyl-4-vinylpyridinium iodide-co-acrylonitrile) (membrane 5 ) (quarternized fraction, 100%; mol fraction of pyridinium moiety, 0.038). It was found that the introduction of cationic charge site into the membrane was one of feasible methods to obtain suitable membranes for water permselective membranes in the separation of water–ethanol mixtures.