Membranes based on polyimide–polyaniline nanocomposites for pervaporation of organic mixtures

Polyimide–polyaniline nanocomposites were obtained by mixing poly{[4,4′‐bis(4″‐N‐phenoxy)diphenylsulfone]imide‐1,3‐bis(3,4‐dicarboxyphenoxy)benzene} (PI) and polyaniline (PANI) solutions in N‐methylpyrrolidone. These solutions were used for the preparation of homogeneous and composite membranes. Uniform distribution of PANI particles in the membranes, resulted from interactions between macromolecules, was confirmed by transmission electron microscopy. Membranes based on PI and PI–PANI were tested in pervaporation of binary organic mixtures: methanol/toluene and methanol/cyclohexane and showed a remarkable selectivity with respect to methanol. In both pervaporation processes, selectivity was improved in PANI‐containing membranes. Interactions between membrane polymers and liquid penetrants (methanol, toluene, and cyclohexane) were studied by measurements of surface tension, sorption, and pervaporation parameters. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterization of poly(dimethylsiloxane)‐poly(methyl hydrogen siloxane) composite membranes for organic water pervaporation separation

Hydrophobic composite membranes with a crosslinked poly(dimethylsiloxane)‐poly(methyl hydrogen siloxane) selective layer were prepared by using a new laboratory made catalyst agent. The pervaporation separation of five organic solvent–water mixtures was carried out with these composite membranes, together with swelling experiments in the same feed mixtures. The volatile organic compounds employed were ethanol, methanol, 1‐butanol, acetone, and ethyl acetate. The pervaporation and swelling experiments revealed that both the 1‐butanol and the ethyl acetate solutions showed the highest affinity for the composite membrane. When these components were employed as feed solutions, the membranes showed both high selectivity and high permeation. Mechanical–dynamical experiments of swollen and nonswollen composite membranes were also performed. The relaxation spectra were analyzed in terms of the interaction of the components of the different mixtures with the composite membrane, and the free volume corresponding to the each sample was obtained. Once the membranes had reached an equilibrium swelling, a decrease in the free volume was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 546–556, 2001     

Membranes based on poly(styrene-N-phenylmaleimide)/poly(2,6-dimethyl-1,4-phenylene oxide) blends

Blend membranes were prepared by casting chloroform solutions of mixtures of styrene-N-phenylmaleimide copolymer containing ca. 10 mol % imide units with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and their phase behavior was evaluated. At a content of 20% PPO, the membranes were homogeneous; those having 40 or more % PPO exhibited phase separation. Membranes made of the parent polymers and their blends were tested in the pervaporation of aqueous ethanol solutions; permeabilities to oxygen, nitrogen, and carbon dioxide were also determined. The pervaporation characteristics and gas transport properties are discussed considering the interactions of polymer chains and the phase structure of the membranes. © 1995 John Wiley & Sons, Inc.     

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     

Chemical modification of poly(substituted-acetylene). IV. Pervaporation of organic liquid/water mixture through poly(1-phenyl-1-propyne)/polydimethylsiloxane graft copolymer membrane

Poly(1-phenyl-1-propyne)/polydimethysiloxane (PPP/PDMS) graft copolymer membranes having various PDMS content were prepared by solvent casting method, and the permeation characteristics at pervaporation were examined upon the aqueous solutions containing organic liquids such as alcohols, acetone, dioxane, acetonitrile, pyridine, and DMF. At pervaporation of ethanol/water mixture, preferential permeation of ethanol was observed for all the copolymer membranes, although PPP membrane showed water permselectivity. The permselectivity of the copolymer membrane also depended on operation temperature, but was independent on the thickness of the membrane. Furthermore, an excellent permselectivity of organic liquids was observed at the pervaporation of several organic liquid/water mixtures except in the case of DMF/water mixture. Observed high selectivity is thought to be due to the depression of the membrane swelling and the high solubility of the liquids into the membrane.     

Synthesis,characterization, and pervaporation properties of segmented poly(urethane‐urea)s

Poly(urethane‐urea)s (PUUs) from 2,4‐tolylene diisocyanate (2,4‐TDI), poly(oxytetramethylene)diols (PTMO) or poly(butylene adipate)diol (PBA), and various diamines were synthesized and characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and density measurements. Transport properties of the dense PUU‐based membranes were investigated in the pervaporation of benzene–cyclohexane mixtures. It was shown that the pervaporation characteristics of the prepared membranes depend on the structure and length of the PUU segments. The PBA‐based PUUs exhibit good pervaporation performance along with a very good durability in separation of the azeotropic benzene–cyclohexane mixture. They are characterized by the flux value of 25.5 (kg μm m⁻² h⁻¹) and the separation factor of 5.8 at 25°C, which is a reasonable compromise between the both transport parameters. The PTMO‐based PUUs display high permeation flux and low selectivity in separation of the benzene‐rich mixtures. At the feed composition of 5% benzene in cyclohexane, their selectivity and flux are in the range of 3.2 to 11.7 and 0.4 to 40.3, respectively, depending on the length of the hard and soft segments. The chemical constitution of the hard segments resulting from the chain extender used does not affect the selectivity of the PUU membranes. It enables, however, the permeability of the membranes to be tailored. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1615–1625, 1999     

Pervaporation of 1,2‐dimethoxyethane from aqueous solutions by crosslinked oligosilylstyrene–poly(dimethylsiloxane) composite membranes

Crosslinked oligosilylstyrene–poly(dimethylsiloxane) composite membranes were used to separate 1,2‐dimethoxyethane (1,2‐DME) from dilute aqueous solutions through a pervaporation process. The composite membranes were prepared through the casting of solutions of H‐terminated oligosilylstyrene and vinyl‐terminated poly(dimethylsiloxane) onto the surfaces of polysulfone ultrafiltration membranes. A crosslinked poly(dimethylsiloxane) gel was generated through the reaction of H‐terminated oligosilylstyrene and vinyl‐terminated poly(dimethylsiloxane), with a platinum complex used as a catalyst. The pervaporation characteristics of the composite membranes were investigated with respect to the feed composition of 1,2‐DME, the feed temperature, the downstream pressure, and the top‐layer thickness of the composite membranes. The composite membranes exhibited preferential selectivity to 1,2‐DME. Depending on the operation conditions, the separation factor and permeation rate of 1,2‐DME were 55–184 and 0.31–3.3 g/m² h, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2284–2294, 2004     

Pervaporation of 50 wt % ethanol–water mixtures with poly(1‐trimethylsilyl‐1‐propyne) membranes at high temperatures

Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) membranes have been used to separate ethanol–water mixtures by pervaporation. This polyacetylene is known to present high affinity toward ethanol, showing high selectivity and ethanol permeation flux. The performance of this polymer in the separation of alcohol–water solutions has been evaluated over long periods (572 h) at a high temperature (75°C) to examine the deterioration of the transport properties in the separation of 50 wt % ethanol–water solutions. Although PTMSP membranes present good characteristics for the separation of gases and liquid mixtures, their organic selectivity decrease with the operating time because of the relaxation processes of the polymeric chains, which affect the free volume of the polymer, the deterioration being more evident for concentrated solutions. The effects of the operation temperature on the characteristic parameters of pervaporation have also been studied to establish how this variable affects the performance of PTMSP membranes. The selectivity increases slightly with the operation temperature, but the effect of the temperature on the separation factor decreases as membranes are degraded with the operation time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2843–2848, 2007     

Pervaporation of organic solvents by poly[bis(2,2,2-trifluoroethoxy) phosphazene] membrane

The permeation and pervaporation behaviour of water and several organic solvents through poly[bis(2,2,2-trifluoroethoxy)phosphazene] (PBFP) membrane have been investigated in the temperature range from 42 to 80°C. The steady-state permeation fluxes of the solvents increased in the following order: methanol > ethanol > benzene > water > cyclohexane. An Arrhenius plot of permeation flux of water suddenly changed in its gradient at about 66–70°C, which corresponds closely to the T(1) transition temperature (75°C) of PBFP studied. Interestingly, in the pervaporation of water-methanol mixtures, methanol permeated more rapidly through the membrane than did water; however, the pervaporation of water-ethanol mixtures showed poor permselectivties. In the case of an athermal mixture of methanol and ethanol, the fluxes of methanol and ethanol indicated convex and concave curves, respectively, to the axis of methanol concentration; thus the separation characteristics of this system were slightly better than those of a simple distillation technique. The pervaporation of benzene-cyclohexane mixtures showed excellent permselectivty enrichment in benzene resulting in a separation factor of 12.     

Vapor Permeation and Pervaporation of Aqueous 2‐Propanol Solutions through the Torlon® Poly(amide imide) Membrane

Abstract

In the present study, vapor permeation and pervaporation of aqueous 2‐propanol mixtures were investigated using Torlon^® poly(amide imide) as a membrane material. Torlon membranes preferentially permeated H₂O from aqueous 2‐PrOH mixtures both by vapor permeation and pervaporation. Diffusion experiments led to the conclusion that both solubility selectivity and diffusivity selectivity showed a preference for H₂O. Solubility selectivity is by far the dominant factor governing permselectivity, and as a result, Torlon membranes showed permselectivity toward water in vapor permeation and pervaporation. The present study showed that Torlon^® poly(amide imide) is a membrane material potentially applicable to the dehydration of water miscible organics.     

Dehydration of light oil by pervaporation using poly(vinyl alcohol)–poly(acrylic acid‐co‐maleic acid) membranes

A new blended membrane was prepared and tested by pervaporation of light oil, a mixture of five alcohols plus water. The blended membrane was synthesized by blending poly(vinyl alcohol) and poly(acrylic acid‐co‐maleic acid) sodium salt in the presence of sulfuric acid to dope the reaction. We tested several membranes in order to choose the adequate composition to have the best permselectivity. The PVA(60)–PAA‐co‐maleic acid(40) membrane was selected as it was found to be highly selective. Sorption experiments were performed using binary and ternary water–alcohol solutions. The influence of temperature and feed composition on the selectivity and flux in pervaporation was investigated for two different binary mixtures (water/ethanol, water/isobutanol) and one ternary system (water/ethanol/isobutanol). This membrane presents good permselective properties, high water flux, and good selectivity and can even be used for high‐water activities The performances of this new membrane were compared to those obtained with the PVA(90)–PAA(10) membrane synthesized recently: The fluxes observed for the water–ethanol separation were of the same order of magnitude but the selectivity was found to be much higher. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1709–1716, 2002     

Pervaporation Separation of Benzene/Cyclohexane Mixtures by Poly(vinyl chloride) Membranes

Sorption and pervaporation of benzene/cyclohexane mixtures were studied by using poly(vinyl chloride) (PVC) polymer. The effects of composition of benzene/cyclohexane mixture and temperature on sorption and pervaporation characteristics were determined at 30, 40, and 50 °C for the membranes containing 8 wt% PVC polymer. Liquid feed composition effects on the flux and the selectivity were determined for two different membranes at 30 °C. The membranes that were prepared from the solutions containing 4 wt% and 8 wt% PVC polymer have thicknesses of 30 μm and 50 μm, respectively. Membrane thickness changes with polymer content as expected. Total sorption increased with increasing concentration of benzene. Increasing the concentration of benzene resulted in increasing flux as well as decreasing selectivity also. Fluxes were increased and selectivity decreased with increasing temperature. The selectivity was not affected significantly with varying amounts of polymer in the casting solution but the flux decreased with increasing amount of polymer in the casting solution.     

藻朊酸钠渗透汽化膜分离有机液／水混合物

研究了藻朊酸钠均质膜及藻朊酸钠／酸丙烯腈复合膜的渗透汽化特性。发现它们对甲醇、乙醇、异丙醇、丙酮、四氢呋喃（ＴＨＦ）、二氧六环、丙三醇等有机溶剂与水的混合望远镜水优选 透过，其渗透通量与选择分离系数都非常高。复合膜与均质膜相比，通量成倍增加，除甲醇／水体系外，对其他体系的分离系数不大，对二氧六环／水体系的分离系数复合膜更高。三种藻朊酸钠样品对乙醇／水，二氧六环／水的透过分离性能有所差异，对此，从膜     

Effect of polystyrene stars with fullerene C60 cores on pervaporation properties of poly(phenylene oxide) membrane

Star‐shaped macromolecules with six arms of polystyrene grafted onto a fullerene C₆₀ core, or fullerene‐containing polystyrene (FPS), were used for the modification of poly(phenylene oxide) (PPO) and the preparation of a dense thin‐film membrane. The membrane structure was studied using scanning electron microscopy. The effect of FPS modifier on membrane density and mass transfer of methanol and ethylene glycol through the membrane was studied. Sorption and pervaporation tests were used to determine degree of sorption, diffusion coefficients, flux through the membrane and separation factor. In the pervaporation of a methanol–ethylene glycol mixture over the concentration range of 10–30 wt% methanol in the feed, all membranes showed high affinity to methanol. The separation factor reached a maximum at 5 wt% FPS in the membrane. The PPO/FPS membranes exhibit the best separation properties when the feed is enriched with ethylene glycol. © 2016 Society of Chemical Industry     

Chemical modification of poly(substituted-acetylene). V. Alkylsilylation of poly(1-trimethylsilyl-1-propyne) and improved liquid separating property at pervaporation

In order to improve the separation characteristic at pervaporation, the introduction of several kinds of trialkylsilyl groups into poly(1-trimethylsilyl-1-propyne) (PTMSP) was achieved via metalation of PTMSP followed by treating with trialkylchlorosilanes to afford trialkylsilylated PTMSP. Ratio of TMSP monomer unit and trialkylsilylated unit, x/y, was in the range of 95/5 to 80/20. All the chemically modified PTMSP membranes showed ethanol permselectivity at pervaporation of aqueous ethanol solution. Introduction of appropriate length of alkyl groups (methyl, ethyl, propyl, butyl, hexyl, octyl, and decyl groups) into PTMSP effectively enhanced the selectivity. However, excess introduction of octyl and decyl groups or introduction of dodecyl and octadecyl groups caused decrease of selectivity, of which the value was smaller than that of PTMSP membrane. Furthermore, acetone, acetonitrile, dioxane, and isopropanol were efficiently separated from their aqueous solutions at pervaporation through trimethylsilylated PTMSP membrane.     

Poly(vinyl alcohol)/poly(vinyl pyrrolidone) interpenetrating polymer network: Synthesis and pervaporation properties

Novel interpenetrating polymer network membranes were made from poly(vinyl alcohol)/poly(vinyl pyrrolidone) blends of different compositions. The two polymer components were independently crosslinked chemically with glutaraldehyde and photochemically with 4,4′‐diazostilbene‐2,2′‐disulfonic acid disodium salt. The membrane performances were studied in pervaporation of tetrahydrofuran (THF)/water and THF/methanol mixtures. It was found that the membranes were excellent in THF dehydration, but much less efficient for the separation of THF/methanol mixtures. The pervaporation results were consistent with the membrane swelling data. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2808–2814, 2003     

Formation of multilayer poly(acrylic acid)/poly(vinylidene fluoride) composite membranes for pervaporation

Dual‐ and multilayer composite membranes, consisting of poly(acrylic acid) (PAA) and poly(vinylidene fluoride) (PVDF), were synthesized by the plasma‐induced polymerization technique. The dual‐layer membrane had a dense PAA layer grafted onto a microporous PVDF substrate, whereas in the multilayer membranes, the grafted PAA and the PVDF layers were arranged in an alternating sequence (e.g., PAA/PVDF/PAA and PAA/PVDF/PAA/PVDF/PAA). These membranes were used in a pervaporation process to separate ethanol–water solutions. For the dual‐layer membranes, the results indicated that the separation factor increased and the permeation flux decreased with increasing amounts of grafted PAA. For the case of grafting yield < 0.6 mg/cm², the composite membrane demonstrated poor separation. As the grafting yield reached 0.85 mg/cm², a sharp increase of the separation factor was observed. For the multilayer membranes, the pervaporation performances were very good, with high separation factors (on the order of 100) and reasonable permeation fluxes over a wide ethanol concentration range. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2266–2274, 2004     

Effect of Residual Solvent on Physicochemical Properties of Poly(Phenylene Isophtalamide) Membrane

The influence of a plasticizer in the form of the residual solvent dimethylacetamide on pervaporation and sorption properties of membranes based on poly(phenylene isophtalamide) (PA) was investigated. To analyze the influence of the plasticizer on membrane transport properties, pervaporation of binary water–ethyl acetate mixtures was studied. The method of sorption calorimetry was used to investigate water sorption properties of the studied membranes and PA powder. Moreover, to characterize the PA membranes, contact angle measurements and thermogravimetric analysis (TGA) were applied. It is shown that the presence of a residual organic solvent significantly changes the sorption and transport characteristics of the membranes. The residual organic solvent increases the amount of water absorbed by the polymer membrane. In pervaporation of water/ethyl acetate mixtures, the presence of the residual solvent dimethylacetamide makes the membrane more permeable but less selective for water separation.     

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     

Polysiloxaneimide membranes for removal of VOCs from water by pervaporation

For the separation of volatile organic compounds (VOCs) from water by pervaporation, three polysiloxaneimide (PSI) membranes were prepared by polycondensation of three aromatic dianhydrides of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA) with a siloxane‐containing diamine. The PSI membranes were characterized using ¹H‐NMR, ATR/IR, DSC, XRD, and a Rame‐Hart goniometer for contact angles. The degrees of sorption and sorption selectivity of the PSI membranes for pure organic compounds and organic aqueous solutions were investigated. The pervaporation properties of the PSI membrane were investigated in connection with the nature of organic aqueous solutions. The effects of feed concentration, feed temperature, permeate pressure, and membrane thickness on pervaporation performance were also investigated. The PSI membranes prepared have high pervaporation selectivity and permeation flux towards hydrophobic organic compounds. The PSI membranes with 150‐μm thickness exhibit a high pervaporation selectivity of 6000–9000 and a high permeation flux of 0.031–0.047 kg/m² h for 0.05 wt % of the toluene/water mixture. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2691–2702, 2000