Pervaporation and solute separation through semi-interpenetrating and interpenetrating polymer network membranes prepared from poly(4-vinylpyridine) and poly(glycidyl methacrylate)

Semi-interpenetrating (SPN) and interpenetrating polymer network (IPN) membranes were prepared from a mixture system of poly(4-vinylpyridine) (P4VP) and poly(glycidyl methacrylate) (PGMA) by quaternizing crosslinking of P4VP with 1,4-dibromobutane (DBB) and by simultaneous crosslinking of P4VP with DBB and PGMA with tetraethylenepentamine (TEPA), respectively. The difference between SPN and IPN was demonstrated by IR, tensile strength, and dimension stability. The membrane performance in pervaporation (PV) for ethanol–water mixtures and reverse osmosis (RO) was investigated. The polymer mixture of 1 : 1 on a monomer base with 30 mol % DBB on the 4VP unit and 5.6–7.5 mol % (8–10 wt %) TEPA on the GMA unit gave an optimum membrane performance. Those crosslinked membranes were stronger than was the cellulose acetate membrane, mostly owing to the PGMA chains, and exhibited a high separation factor for the azeotropic feed in PV. IPN membranes generally showed a performance higher than that of the SPN ones. An attempt to improve the product rate was made by the addition of a water-soluble polymer to the membrane on casting. The separation factor for solubility in the membrane at the feed side dominated the overall separation factor, particularly for feeds of higher ethanol concentrations. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 69: 1953–1963, 1998     

Poly(acrylic acid)–poly(vinyl alcohol) semi- and interpenetrating polymer network pervaporation membranes

A series of poly(acrylic acid) (PAA)–poly(vinyl alcoho) (PVA) semiinterpenetrating (SIPN) and interpenetrating (IPN) polymer network membranes were prepared by crosslinking PVA alone or by crosslinking both PVA and PAA. Glutaraldeyde and ethylene glycol were used as crosslinking agents for the PVA and PAA networks, respectively. The presence of PAA increases the permeability of the membranes while the presence of PVA improves their mechanical and film-forming properties. The mechanical properties of the membranes were investigated via tensile testing. These hydrophilic membranes are permselective to water from ethanol–water mixture and to ethanol from ethanol–benzene mixtures. The IPN membranes were employed for the former mixtures and the SPIN membranes for the latter, because the IPN ones provided too low permeation rates. The permeation rates and seperation factors were determined as functions of the IPN or SIPN composition, feed composition, and temperature. For the azeotropic ethanol–water mixture (95 wt % ethanol), the separation factor and permeation rate at 50°C of the PAA-PVA IPN membrane, containing 50 wt % PAA, were 50 and 260 g/m²h, respectively. For the ethanol–benzene mixture, the PAA–PVA SIPN membranes had separation factors between 1.4 and 1200 and permeation rates between 6 and 550 g/m²h, respectively, depending on the feed composition and temperature. © 1996 John Wiley & Sons, Inc.     

Blend membranes of chitosan and poly(vinyl alcohol) in pervaporation dehydration of isopropanol and tetrahydrofuran

Blend membranes of a natural polymer, chitosan, with a synthetic polymer, poly(vinyl alcohol) (PVA), were prepared by solution casting and crosslinked with a urea formaldehyde/sulfuric acid (UFS) mixture. Chitosan was used as the base component in the blend system, whereas PVA concentration was varied from 20 to 60 wt %. Blend compatibility was studied by differential scanning calorimetry, and Fourier transform infrared spectroscopy was used to study membrane crosslinking. Membranes were tested for pervaporation dehydration of isopropanol and tetrahydrofuran (THF) at 30°C in close proximity to their azeotropic compositions. Membrane performance was assessed by calculating flux and selectivity. Swelling experiments performed in water + organic mixtures at 30°C were used to explain the pervaporation results. The blend membrane containing 20 wt % PVA when tested for 5 and 10 wt % water–containing THF and isopropanol feeds exhibited selectivity of 4203 and 17,991, respectively. Flux increased with increasing concentration of water in the feed. Selectivity was highest for the 20 wt % PVA‐containing blend membrane. The results of this study are unique in the sense that the crosslinking agent used—the UFS mixture—was novel. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1918–1926, 2007     

Preparation and characterization of CMCS/PVA blend membranes and its sorption and pervaporation performance (I)

Novel pervaporation (PV) membranes for ethanol dehydration were prepared by blend poly(vinyl alcohol) (PVA) and carboxymethyl chitosan (CMCS), followed by the crosslinking reaction with glutaraldehyde; the structure and miscibility of the blend membranes were characterized by Fourier transform infrared, X‐ray diffraction, and differential scanning calorimetry; the results indicated that the blends were miscible. The effect of feed concentration, operation temperature, crosslinking agent content, etc. on sorption performance and PV performance of the blend membrane is investigated. The membrane of CMCS/PVA blend ratio of 8 : 2 exhibited a high separation factor of 2959 with a reasonably high water flux value of 0.14 kg m^?2h^?1 at the azeotropic feed composition (95 wt % of ethanol) at a temperature of 45°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Properties and pervaporation performance of poly(vinyl alcohol) membranes crosslinked with various dianhydrides

In this work, three dianhydrides with similar chemical structures, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), 4,4′‐oxydiphthalic anhydride (ODPA), and pyromellitic dianhydride (PMDA), are employed for the crosslinking modification of poly(vinyl alcohol) (PVA) membranes for ethanol dehydration via pervaporation. The changes in crosslinking degree, surface hydrophilicity, and glass‐transition temperature are investigated and compared. Compared to the pure PVA membrane, all crosslinked membranes show higher fluxes but lower separation factors, because of the higher fractional free volume and the lower hydrophilicity by the crosslinking of the PVA matrix, respectively. In addition, all crosslinked PVA membranes exhibit similar flux, and the separation factor presents a decreasing order of PVA/PMDA‐2 > PVA/ODPA‐2 > PVA/BTDA‐2, which is in the reverse order of their hydrophilicity, probably because of the reduction in the swelling resistance. With the PMDA content increasing from 0.01 to 0.04 mol/(kg PVA) in the PVA/PMDA crosslinked membranes, the crosslinking degree is enhanced and the hydrogen bonding is weakened, resulting in a flux increase from 120.2 to 190.8 g m^?2 h^?1, but the separation factor declines from 306 to 58. This work is believed to provide useful insight on the chemical modification of PVA membranes for pervaporation and other membrane‐based separation applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46159.     

Modified polydimethylsiloxane/polystyrene blended IPN pervaporation membrane for ethanol/water separation

In this article a modified polydimethylsiloxane (PDMS) blended polystyrene (PS) interpenetrating polymer network (IPN) membranes supported by Teflon (polytetrafluoroethylene) ultrafiltration membrane were prepared for the separation of ethanol in water by pervaporation application. The relationship between the surface characteristics of the surface‐modified PDMS membranes and their permselectivity for aqueous ethanol solutions by pervaporation are discussed. The IPN supported membranes were prepared by sequential IPN technique. The IPN supported membrane were tested for the separation performance on 10 wt % ethanol in water and were characterized by evaluating their mechanical properties, swelling behavior, density, and degree of crosslinking. The results indicated that separation performance, mechanical properties, density, and the percentage of swelling of IPN membranes were influenced by degree of crosslink density. Depending on the feed temperature, the supported membranes had separation factors between 2.03 and 6.00 and permeation rates between 81.66 and 144.03 g m^?2 h^?1. For the azeotropic water–ethanol mixture (10 wt % ethanol), the supported membrane had at 30°C a separation factor of 6.00 and a permeation rate of 85 g m^?2 h^?1. Compared to the PDMS supported membranes, the PDMS/PS IPN supported blend membrane ones had a higher selectivity but a somewhat lower permeability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

热处理条件对PVA/PAN和PPVA/PAN渗透汽化复合膜分离性能的影响

制备了以聚乙烯醇（PVA）、磷酸酯化聚乙烯醇（PPVA）和活性分离层的PVA／PAN、PPVA／PAN渗透汽化复合膜并用于乙醇－水恒沸混合物的分离。考察了热处理条件对复合膜分离性能及吸附性能的影响。结果表明,复合膜的分离性能主要是由热处理温度决定的,并且,PPVA／PAN复合膜比PVA／PAN复合膜具有更好的分离性能。确定了最佳的热处理条件,对于PVA／PAN复合膜：在403K下,热处理时间不小于4h,对于PPAV／PAN复合膜：在423K下,热处理时间不小于2h。     

Crosslinked blended poly(vinyl alcohol)/N-methylol nylon-6 membranes for the pervaporation separation of ethanol–water mixtures

Crosslinked blended membranes of poly(vinyl alcohol) (PVA) and N-methylol nylon-6 were prepared either by thermal crosslinking at 180°C or by chemical crosslinking with maleic acid. The pervaporation performance for the separation of ethanol–water mixtures of these membranes was investigated in terms of feed concentration, PVA content, and crosslinking agent content. The pervaporation performance of two differently crosslinked membranes was strongly influenced by the nature of the crosslinkage. Significant improvement in the pervaporation separation index can be achieved for chemically crosslinked membranes. From the comparison between the pervaporation and sorption tests, it is suggested that, for hydrophilic membranes, sorption properties dominate the pervaporation performance at feed solutions of higher water content, while diffusion properties govern at feed solutions of higher ethanol content. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 317–327, 1998     

Cellulose–poly(acrylamide or acrylic acid) interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures

A new type of interpenetrating polymer network (IPN) pervaporation membranes based on cellulose and synthetic polymers was developed. They were prepared by free-radical polymerization of acrylamide or acrylic acid in the presence (or absence) of the crosslinking agent (allyldextran or N,N′-methylenebisacrylamide) within cellophane films swollen in the reaction mixture. The swelling behavior of these membranes in water–ethanol solutions and their separation characteristics were investigated depending on the polyacrylamide (PAAm) or poly(acrylic acid) (PAA) content in the IPN (C_p) and for ionic cellulose–PAA membranes depending on the degree of neutralization of carboxylic groups and on the type of counterions. IPN membranes were selective over a wide range of ethanol concentration in the feed. The separation factor (α) and the permeation rate (P) significantly improved with increasing C_p in IPN membranes, especially for the cellulose–PAA(K⁺ form) membranes (for 86% EtOH feed at 50°C, and α and P values reached 1500 and 1.6 kg/m² h, respectively). The results for ionic and nonionic IPN membranes were compared. The separation characteristics of membranes were in good correlation with their swelling behavior. The α values of the membranes depended on the affinity of the IPN polymer chains functional groups for water. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 761–769, 1998     

Characterization of sodium alginate and poly(vinyl alcohol) blend membranes in pervaporation separation

By blending a rigid polymer, sodium alginate (SA), and a flexible polymer, poly(vinyl alcohol) (PVA), SA/PVA blend membranes were prepared for the pervaporation separation of ethanol–water mixtures. The rigid SA membrane showed a serious decline in flux and a increase in separation factor due to the relaxation of polymeric chains, whereas the flexible PVA membrane kept consistent membrane performance during pervaporation. Compared with the nascent SA membrane, all of the blend membranes prepared could have an enhanced membrane mobility by which the relaxation during pervaporation operation could be reduced. From the pervaporation separation of the ethanol–water mixtures along with the temperature range of 50–80°C, the effects of operating temperature and PVA content in membrane were investigated on membrane performance, as well as the extent of the relaxation. The morphology of the blend membrane was observed with PVA content by a scanning electron microscopy. The relaxational phenomena during pervaporation were also elucidated through an analysis on experimental data of membrane performance measured by repeating the operation in the given temperature range. SA/PVA blend membrane with 10 wt % of PVA content was crosslinked with glutaraldehyde to enhance membrane stability in water, and the result of pervaporation separation of an ethanol–water mixture through the membrane was discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:949–959, 1998     

Properties of modified poly(vinyl alcohol) membranes prepared by the grafting of new polyelectrolyte copolymers for water–ethanol mixture separation

For the preparation of a water‐selective membrane for the pervaporation separation of an azeotropic solution, a series of grafted copolymers were synthesized by the reaction of poly(vinyl alcohol) (PVA) with poly(sodium salt styrene sulfonic acid‐co‐maleic acid) (PSStSA‐co‐MA). The esterification was performed between the hydroxyl groups of PVA and the carboxylic groups of the copolymer with a heat treatment. PSStSA‐co‐MA was prepared with sodium salt styrene sulfonic acid and maleic anhydride copolymerization in dimethyl sulfoxide with azobisisobutyronitrile as an initiator. The reaction mechanism and resultant structure were confirmed with IR spectra. The effect of the heat‐treatment time on the gel content was investigated. The permeation flux decreased and the separation factor increased as the crosslinking agent content rose. A membrane containing 15 wt % PSStSA‐co‐MA was used for water–ethanol azeotropic solution pervaporation at 30°C, and a flux of 0.43 kg/m² h and a separation factor of 190 were obtained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2854–2859, 2002     

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 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.     

Enhancement of pervaporation performance of composite membranes through in situ generation of silver nanoparticles in poly(vinyl alcohol) matrix

Composite membranes were prepared from an aqueous solution of poly(vinyl alcohol) (PVA) and silver sulphate. The silver nanoparticles were generated in situ before crosslinking PVA matrix by reduction of silver ions using sodium borohydride. Physico‐chemical properties of the resulting composite membranes were studied using Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy (UV–vis), thermogravimetric analysis (TGA), Wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), and universal testing machine (UTM). The UV–vis spectrum shows a single peak at 410 nm due to surface plasmon absorption of silver nanoparticles. This surely specified that silver nanoparticles are generated in PVA matrix. The membranes were under go pervaporation (PV) for separation of water from isopropanol at different temperatures. The results indicated that hydrophilicity and amorphous nature of the membranes were increased with increasing silver nanoparticles in PVA matrix. The swelling and separation performance of the membranes were studied. Both permeation flux and separation factor were increased with increasing silver nanoparticles in PVA matrix. The results showed that the membrane containing 2.5 mass% of Ag salt exhibited excellent PV performance. The values of total flux and flux of water are almost closed to each other, indicating that membranes could be effectively used to break the azeotropic point of water‐isopropanol. The long‐term test was performed at room temperature and ascertained that membranes were durable up to 30 days for the dehydration of IPA. On the basis of the estimate Arrhenius activation energy values, the efficiency of the membranes was discussed. The calculated ΔH_s values are negative for all the membranes, indicating that Longmuir's mode of sorption is predominant. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41248.     

Free volume defects and transport properties of mechanically stable polyhedral oligomeric silsesquioxane embedded poly(vinyl alcohol)‐poly(ethylene oxide) blend membranes

Polymer membrane based gas transport and pervaporation processes are fast growing areas in separation technology and have received wide attention as areas of ‘clean technology’. Mechanically stable novel polyhedral oligomeric silsesquioxane (POSS) embedded poly(vinyl alcohol) (PVA)/poly(ethylene oxide) (PEO) blend membranes were prepared by solution blending followed by casting. The addition of carboxymethyl cellulose enhanced the interfacial activities of the PVA and PEO blends. The peripheral organic substituent on POSS plays a key role in achieving compatibility with polymers whereas the rigid Si–O–Si core of POSS imparts high mechanical strength. Compared to PVA membrane, poly(ethylene glycol) and octa(tetramethylammonium) functionalized POSS embedded PVA/PEO membranes exhibit 680% and 580% enhancement in Young's modulus as well as 130% and 140% improvement in tensile strength respectively. The Einstein, Kerner and Frankel–Acrivos models were applied to compare the experimental and theoretical Young's modulus of PVA‐PEO/POSS membranes. The presence of an ethylene oxide tail on POSS as well as PEO in the blend membrane enhances the CO₂ affinity of the membrane. The presence of a hydrophilic functional group on the POSS improves the hydrophilicity of the membrane and produces more binding sites for water molecules in the membrane during the pervaporation separation of a tetrahydrofuran–water azeotropic mixture. The transport properties of the membrane are further elucidated by means of free volume defect analysis carried out by positron annihilation lifetime spectroscopy and coincidence Doppler broadening spectroscopy. © 2019 Society of Chemical Industry     

Sodium alginate–poly(hydroxyethylmethacrylate) interpenetrating polymeric network membranes for the pervaporation dehydration of ethanol and tetrahydrofuran

Interpenetrating polymeric network (IPN) membranes of sodium alginate (NaAlg) and various amounts of poly(hydroxyethylmethacrylate) (PHEMA) have been prepared and tested for the pervaporation dehydration of ethanol and tetrahydrofuran (THF). The presence of hydrophilic PHEMA in the IPN matrix was found to be responsible for increase in membrane selectivity to water. NaAlg–PHEMA IPN membrane containing 20 wt % of PHEMA exhibited a selectivity of 571 to water for the water–ethanol mixture and 857 for water–THF mixture. These data are much better than those observed for the pristine NaAlg membrane. However, flux of the IPN membranes was smaller than that of pristine NaAlg membrane. Comparatively higher flux values were observed for water–THF mixture than for water–ethanol mixture. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3324–3329, 2006     

Thermal characteristics of poly(vinyl alcohol) and poly(vinylpyrrolidone) IPNs

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and 1‐vinyl‐2‐pyrrolidone (VP) were prepared by radical polymerization using 2,2‐dimethyl‐2‐phenylacetophenone (DMPAP) and methylene bisacrylicamide (MBAAm) as initiator and crosslinker, respectively. The thermal characterization of the IPNs was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depressions of the melting temperatures of PVA segments in IPNs were observed with increasing VP content via the DSC. The DEA was employed to ascertain the glass transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_gs indicating the presence of phase separation in the IPN. The thermal decomposition of IPNs was investigated using TGA and appeared at near 270°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1844–1847, 2002     

Modification of poly(vinyl alcohol) membranes using sulfur-succinic acid and its application to pervaporation separation of water–alcohol mixtures

For the purposes of the water-selective membrane material development for pervaporation separation, we crosslinked poly(vinyl alcohol) (PVA) with sulfur-succinic acid (SSA), which contains —SO₃OH, by heat treatment and investigated the effect of the crosslinking density on the separation of water–alcohol mixtures by pervaporation technique. The crosslinking reaction between PVA and SSA was characterized through Fourier transform infrared spectroscopy and differential scanning calorimetry tests by varying the amount of the crosslinking agent, the reaction temperature, and the swelling measurements of each pure component. The separation performance of the water–methanol mixture is not good due to the existence of sulfonic acid, hydrophilic group, in the crosslinking agent. However, for the water–ethanol mixture, the flux of 0.291 kg/m²h and the separation factor of 171 were obtained at 70°C when PVA-crosslinked membrane containing 7 wt % SSA was used. The same membrane also showed flux of 0.206 kg/m²h and a separation factor of 1969 at the same operating temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1717–1723, 1998     

Pervaporation separation of aqueous organic mixtures through sulfated zirconia‐poly(vinyl alcohol) membrane

Sulfated zirconia‐poly(vinyl alcohol) membranes were prepared, and pervaporation performances for aqueous organic mixtures were investigated. These hydrophilic membranes were formed by crosslinking poly(vinyl alcohol) (PVA) with the solid acid of sulfated zirconia by an acid‐catalyzed reaction. The pervaporation performances were measured as a function of the content ratio of sulfated zirconia to PVA, which affected the degree of swelling for water and the crosslinking density of the membrane. The membrane selectivity in pervaporation of aqueous organic mixtures increased in order of acetic acid < ethanol < 2‐ethoxyethanol without sacrificing the permeation rate, depending on their feed compositions. The effects of feed temperature and concentration on the membrane performance were also significant. It was found that sulfated zirconia in the membrane preparation played an important role as a filler material as well as an effective crosslinking or insolubilization agent in improving and controlling the membrane performance, i.e., permeation rate and selectivity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1450–1455, 2001     

Poly(vinyl alcohol)/Carboxyl Graphene Membranes for Ethanol Dehydration by Pervaporation

Carboxyl graphene (CG) with two functions of hybridization and crosslinking was incorporated into poly(vinyl alcohol) (PVA) matrix to form PVA/CG mixed-matrix membranes (MMMs). The membranes demonstrated excellent mechanical properties and thermal stability. The improved hydrophilicity and formed crosslinking structure led to moderate swelling. The membrane crystallinity decreased and the free volume was promoted with increasing CG loading amount. The pervaporation (PV) separation performance for ethanol dehydration indicated that both permeation flux and separation factor were enhanced simultaneously at the optimum CG loading. Subsequently, the permeation flux continued to increase while the separation factor declined at higher CG loadings.