Preparation and pervaporation performance of 3,3‐bis[4‐(4‐aminophenoxy)phenyl] phthalide based polyimide membranes

A series of novel solvent‐soluble polyimides based on the diamine of 3,3‐bis[4‐(4‐aminophenoxy)phenyl] phthalide (BAPP) were prepared. The effects of the dianhydride structures on the pervaporation performance of aqueous alcohol mixtures through these polyimide membranes were studied. The BAPP‐based polyimide membranes exhibited water permselectivity during all process runs. The permeation rate increased with the addition of bulky groups to the polyimide backbone. The effects of the feed solution concentration, feed solution temperature, and carbon atom number of the feed alcohol on the pervaporation performance were also investigated systematically. Optimum pervaporation results, a separation factor of 22 and a permeation rate of 270 g/m² h, were obtained for a 90 wt % feed aqueous ethanol solution through a 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride polyimide membrane at 25°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2046–2052, 2005     

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     

Permselective Properties for Aqueous Ethanol Solutions through Copolymer Membranes from Benzyl Methacrylate and Polyethylene Glycol Dimethacrylate

Abstract

Copolymer membranes prepared by bulk copolymerization of polyethylene glycol dimethacrylates of three different degrees of polymerization as macromonomer and benzyl methacrylate as comonomer were used for the separation of aqueous ethanol solutions in both pervaporation and evapomeation. The copolymer membranes preferentially permeated water from an aqueous ethanol solution in evapomeation. In pervaporation, ethanol was predominantly permeated from an aqueous ethanol solution through the copolymer membranes containing a long polyethylene glycol (PEG) chain above about 20 wt% PEG content in a copolymer. This result was attributed to a remarkable swelling of the copolymer membrane containing a long PEG chain by the aqueous ethanol solution in pervaporation. In evapomeation, both the separation factors and the permeation rates through these membranes are not much affected by the ethanol concentration in the feed vapor. In pervaporation, they were significantly dependent on the ethanol concentration in the feed solution. The above results are discussed from the viewpoint of the physical structure of the membrane in evapomeation and pervaporation.     

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     

分离有机物水溶液的渗透汽化与汽化渗透膜

该文基于４５篇最新文献，较详细地论述了渗透汽化膜与汽化渗透膜的有机物水溶液分离性能及其影响因素，包括高聚物特征，料液浓度，温度，古游侧压力，膜厚度和操作时间，指出用多数高聚物膜进行渗透汽化操作可以有效地分离多数有机醇，酮，酸，酯，酰胺以及二Ｅ烷，乙腈，吡啶，二甲亚砜和四氢呋喃水溶液；而以壳聚糖及其衍生物膜进行汽化渗透操作则具有更高的分离系数。该文还简要介绍了渗透汽化膜的新应用。为渗透汽化与汽化渗透     

Dehydration of ethanol/water mixtures by pervaporation using soluble polyimide membranes

A series of soluble polyimides derived from 3,3′,4,4′‐benzhydrol tetracarboxylic dianhydride (BHTDA) with various diamines such as 1,4‐bis(4‐aminophenoxy)‐2‐tert‐butylbenzene (BATB), 1,4‐bis(4‐aminophenoxy)‐2,5‐di‐tert‐butylbenzene (BADTB), and 2,2′‐dimethyl‐4,4′‐ bis(4‐aminophenoxy)biphenyl (DBAPB) were investigated for pervaporation separation of ethanol/water mixtures. Diamine structure effect on the pervaporation of 90 wt% aqueous ethanol solution through the BHTDA‐based polyimide membranes was studied. The separation factor ranked in the following order: BHTDA–DBAPB > BHTDA–BATB > BHTDA–BADTB. The increase in molecular volume for the substituted group in the polymer backbone increased the permeation rate. As the feed ethanol concentration increased, the permeation rate increased, while the water concentration in the permeate decreased for all polyimide membranes. The optimum pervaporation performance was obtained by the BHTDA–DBAPB membrane with a 90 wt% aqueous ethanol solution, giving a separation factor of 141, permeation rate of 255 g m^?2 h^?1 and 36 000 pervaporation separation index (PSI) value. Copyright © 2006 Society of Chemical Industry     

Permeation and separation characteristics of alcohol–water mixtures through poly(dimethyl siloxane) membrane by pervaporation and evapomeation

Permeation and separation characteristics for aqueous alcoholic solutions such as methanol/water, ethanol/water and 1-propanol/water were studied using a poly(dimethyl siloxane) membrane by pervaporation and evapomeation. Poly(dimethyl siloxane) membrane preferentially permeated alcohol from aqueous alcoholic solutions in both methods. The concentration of alcohol in the permeate by evapomeation was higher than that by pervaporation. However, the permeation rate for the former method was smaller than that for the latter method. In evapomeation with a temperature difference between the feed solution and the membrane surroundings, when the temperature of the membrane surroundings was kept constant and the temperature of the feed solution was raised, both the permeation rate and the permselectivity for ethanol increased with increasing temperature of the feed solution. On the other hand, as the temperature of the feed solution was kept constant and the temperature of the membrane surroundings was changed, the permeation rate decreased, but the permselectivity for ethanol increased remarkably with dropping temperature in the membrane surrounding. Under permeation conditions of a feed solution of 40°C and a membrane surrounding temperature of ?30°C in evapomeation, an aqueous solution of 10 wt % ethanol in the feed was concentrated to about 90 wt % in the permeate. The permselectivity for alcohol was in the order of methanol <ethanol <1-propanol. The above permeation and separation characteristics are discussed from the viewpoint of the physicochemical properties of the poly(dimethyl siloxane) membrane and the permeating molecules.     

Effects of the polymerization and pervaporation operating conditions on the dehydration performance of interfacially polymerized thin‐film composite membranes

The disadvantage of dense polyamide membranes when applied in the pervaporation separation process is their low permeation rates. To improve the pervaporation performance, polyamide thin‐film composite membranes were prepared via the interfacial polymerization reaction between ethylenediamine (EDA) and trimesoyl chloride (TMC) on the surface of modified polyacrylonitrile (mPAN) membranes. These composite membranes were applied in the pervaporation separation of alcohol aqueous solutions. On the basis of the best pervaporation performance, the desired polymerization conditions for preparing the polyamide thin‐film composite membranes (EDA–TMC/mPAN) were as follows: (1) the respective concentration and contact time of the EDA aqueous solution were 5 wt % and 30 min and (2) the respective concentration of and immersion time in the TMC organic solution were 1 wt % and 3 min. The polyamide thin‐film composite membranes (EDA–TMC/mPAN) exhibited membrane durability when applied in the pervaporation separation of a 90 wt % isopropyl alcohol aqueous solution at 70°C, which indicated that the polyamide thin film composite (TFC) membranes were suitable for the pervaporation separation process at a high operating temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characteristics of permeation and separation of aqueous alcoholic solutions through a poly[bis(2,2,2-trifluoroethoxy)phosphazene] membrane by evapomeation and pervaporation

The characteristics of permeation and separation for aqueous solutions of methanol and ethanol through a poly[bis(2,2,2-trifluoroethoxy)phosphazene] (PBTFP) membrane were studied by pervaporation and evapomeation. In pervaporation technique, methanol was preferentially permeated in all of the feed solution compositions and ethanol was permeated in lower ethanol concentrations of the feed solution. Water was predominantly permeated from the feed solutions with higher ethanol concentration. In evapomeation technique, water was selectively permeated in both all of the feed vapor compositions for aqueous methanol and ethanol solutions. These different permselectivities depended on the feed composition and the membrane permeation technique and could be discussed by a difference in the mechanisms of permeation and separation. It was found that the permeation rate was influenced remarkably by the degree of swelling of the PBTFP membrane and the permselectivity for water of aqueous alcoholic solutions was enhanced by an increasing degree of swelling of the membrane. When the degree of swelling of the membrane with rising permeation temperature was small, both the permeation rate and permselectivity for alcohol in pervaporation and evapomeation increased with the permeation temperature. The above results are discussed considering the PBTFP membrane structure in evapomeation and pervaporation.     

Properties and pervaporation separation of hydroxyl‐terminated polybutadiene‐based polyurethane/poly(methyl metharcylate) interpenetrating networks membranes

Hydroxyl‐terminated polybutadiene (HTPB), 4,4′‐dicyclohexyl methane diiscyanate (H₁₂MDI), and 1,4‐butane diol are used to synthesize polyurethane (PU) solutions by two‐stage process. Interpenetrating networks (IPNs) of HTPB‐based PU and poly(methyl methacrylate) (PMMA) with HTPB/MMA (wt/wt % ratio) = 2.0, 1.5, 1.0, 1.5, 0.8, and 0.6, which are designated as IPN1 to IPN5, respectively, are synthesized by sequential polymerization technique. Thermal properties, tensile strength, and contact angle of membranes increase with the increase of MMA content, while the elongation of membranes show the reverse trend. Characterization of membranes are investigated by C?C/C?O absorption ratio and infrared absorption frequency shiftment. These PU and IPN membranes are used for the separation of ethanol/water and isopropanol/water solution by pervaporation test. IPN3 membrane possesses the largest pervaporation permeability and the separation factor. The pervaporation results of ethanol/water feed has the same trend as that of isopropyl alcohol (IPA)/water solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Permselectivities of aromatic polyamide membranes for aqueous alcohol mixtures in pervaporation

The separation of water/alcohol mixtures was carried out using a series of fluorine-containing aromatic polyamide membranes. Aromatic polyamides were prepared by direct polycondensation of fluorine-containing diamine (2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, BAPPH) and various aromatic diacids. The separation factor toward water increased when the feed ethanol concentration was increased. The solubility of ethanol in aromatic polyamide membrane is higher than that of the water, but the diffusivity of water across the membrane is higher than that of alcohols. A separation factor of 83 and a permeation rate of 262 g/m²h with a 90 wt% feed ethanol concentration at 25 °C was obtained.     

Effect of operation conditions in the pervaporation of ethanol–water mixtures with poly(1‐trimethylsilyl‐1‐propyne) membranes

Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) is known to show preferential permeation of ethanol in the pervaporation of ethanol–water mixture. Although this polymer presents good characteristics for the separation of organic–water solutions, operation conditions and membrane characteristics, such as thickness, affect its pervaporation performance. The effect of temperature and feed concentration on pervaporation was studied. During pervaporation of 10 wt % ethanol–water solution, the separation factor (α_H2O^EtOH) remains almost constant, whereas the permeation flux (F) increases exponentially with operation temperature. On the other hand, the separation factor decreases, whereas the permeation flux increases with ethanol content in the feed mixture. The membrane thickness also affects the performance of PTMSP polymer films: selectivity increases sharply with membrane thickness up to 50 μm, whereas it remains constant for thicker membranes. The permeation flux decreases with membrane thickness in the whole range studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94:1395–1403, 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     

Selective separation of water from aqueous alcohol mixtures through functionalized syndiotactic poly(styrene‐co‐4‐methylstyrene) membranes by pervaporation

The pervaporation performances of a series of functionalized syndiotactic poly(styrene‐co‐4‐methylstyrene) (SPSM) membranes for various alcohol mixtures were investigated. The syndiotactic polystyrene copolymers, poly(styrene‐co‐4‐methylstyrene) (SPSM), were prepared by styrene with 4‐methylstyrene using a Cp*Ti(OCH₃)₃/methyl aluminoxane (metallocene/MAO) catalyst. The effect of functionalization on the thermal properties and polymer structure of the SPSM membranes were also investigated. The crystallinity of the functionalized SPSM membrane is lower than that of the unfunctionalized SPSM membranes. The water molecules preferentially permeate through the SPSM membranes. Compared with unfunctionalized SPSM membranes, the functionalized SPSM membrane effectively increases the membrane formation performances and the pervaporation performances. The optimun pervaporation performance (a separation factor of 510 and permeation rate of 220 g/m²h) was obtained by the bromination of SPSM (SPSMBr) membrane with a 90 wt % aqueous ethanol solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2247–2254, 2002     

Separation of aqueous organic liquid solutions through polymer membranes

Characteristics of permeation and separation for aqueous dimethyl sulfoxide, acetic acid and ethanol solutions through some polymer membranes such as chitosan, poly(vinyl chloride) and poly(dimethyl siloxane) membrane were studied by evapomeation. In temperature difference controlling evapomeation (TDEV), when the temperature of the feed solution was kept constant and the temperature of the membrane surroundings was changed, permselectivity for water increased in the chitosan and poly(vinyl chloride) membranes; in the poly(dimethyl siloxane) membrane the perm-selectivity for ethanol increased while decreasing the temperature of the membrane surroundings. Permeation and separation mechanisms for aqueous organic liquid solutions through the above polymer membranes by the TDEV method are discussed.     

Permeation and separation characteristics of acetic acid/water mixtures through poly(vinyl alcohol‐g‐itaconic acid) membranes by pervaporation,evapomeation, and temperature‐difference evapomeation

In this study, itaconic acid (IA) was grafted onto poly(vinyl alcohol) (PVA) with cerium(IV) ammonium nitrate as an initiator at 45°C. The grafted PVA was characterized with Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. IA‐grafted PVA membranes were prepared with a casting method, and the permeation and separation characteristics of acetic acid/water mixtures were investigated with pervaporation (PV), evapomeation (EV) and temperature‐difference evapomeation (TDEV) methods. The effects of the feed composition, operating temperature, and temperature of the membrane surroundings on the permeation rate and separation factor for the acetic acid/water mixtures were studied. The permeation rates in EV were lower than those in PV, whereas the separation factors were higher. With the TDEV method, the permeation rates decreased and the separation factors increased as the temperature of the membrane surroundings decreased. The prepared membranes were also tested in PV, EV, and TDEV to separate the various compositions of the acetic acid/water mixtures (20–90 wt % acetic acid) at 40°C. The highest separation factor, 686, was obtained in TDEV with a 90 wt % acetic acid concentration in the feed. The activation energies of permeation in PV and EV were calculated to be 8.5 and 10.2 kcal/mol, respectively, for a 20 wt % acetic acid solution. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2322–2333, 2004     

Stabilization of bioethanol recovery with silicone rubber‐coated ethanol‐permselective silicalite membranes by controlling the pH of acidic feed solution

In order to produce highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, techniques to suppress adsorption of succinic acid, which is a chief by‐product of ethanol fermentation and causes the deterioration in pervaporation performance, onto the silicalite crystals was investigated. The amount adsorbed increased as the pH of the aqueous succinic acid solution decreased. The pervaporation performance also decreased with decreasing pH when the ternary mixtures of ethanol/water/succinic acid were separated. Using silicalite membranes individually coated with two types of silicone rubber, pervaporation performance was significantly improved in the pH range of 5 to 7, when compared with that of non‐coated silicalite membranes in ternary mixtures of ethanol/water/succinic acid. Moreover, when using a silicalite membrane double‐coated with the two types of silicone rubber, pervaporation performance was stabilized at lower pH values. In the separation of bioethanol by pervaporation using the double‐coated silicalite membrane, removal of accumulated substances having an ultraviolet absorption maximum at approximately 260 nm from the fermentation broth proved to be vital for efficient pervaporation. Copyright © 2005 Society of Chemical Industry     

Ethanol purification using polyamide‐carbon nanotube composite membranes

This work presents synthesis and characterization of polyamide‐carbon nanotube (CNT) composite membranes for purification of ethanol. The solution‐casting method was applied for preparation of nanocomposite membranes. The nanocomposite membranes were characterized using scanning electron microscopy to ensure the fine dispersion of nanoparticles in polymer matrix. The effect of CNT loading on membrane performance was investigated. The separation performance of synthesized membranes was evaluated in separation of ethanol from ethanol/water mixture using pervaporation. Effect of feed temperature and feed concentration on separation of ethanol was investigated. The results showed that increasing temperature increases flux of ethanol through the membrane, but decreases separation factor. The results also confirmed that the best separation performance can be obtained at CNT loading of 0.5 wt%. Furthermore, a mathematical model was developed to simulate the separation process. The model was based on solving the continuity equation for ethanol in the feed side and membrane. The simulation results were compared with the experimental data and were in good agreement. POLYM. ENG. SCI., 54:961–968, 2014. © 2013 Society of Plastics Engineers     

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     

A study on the characteristics and pervaporation performance of polyamide thin‐film composite membranes with modified polyacrylonitrile as substrate for bioethanol dehydration

To improve the pervaporation performance in separating an aqueous ethanol solution, polyamide thin‐film composite (TFC) membranes (m‐tolidine‐H‐TMC/mPAN) were prepared through the interfacial polymerization reaction between trimesoyl chloride (TMC) and 2,2'‐dimethylbenzidine hydrochloride (m‐tolidine‐H) on the surface of a modified polyacrylonitrile (mPAN) membrane. The effects of the feed ethanol concentration on the pervaporation performance and the durability of m‐tolidine‐H‐TMC/mPAN TFC membranes were investigated. To choose the optimal mPAN membrane as the TFC substrate, the effect of hydrolysis time on the chemical properties and separation performance of an mPAN substrate was also studied. An appropriate hydrolysis time of 15 min was chosen to obtain the mPAN substrate due to the corresponding high permeation flux. The m‐tolidine‐H‐TMC/mPAN TFC membrane exhibited a high pervaporation performance for ethanol dehydration. A positron annihilation lifetime spectroscopy experiment was used to estimate the mean free‐volume radius of the m‐tolidine‐H‐TMC polyamide selective layer, which lay between the radii of the water and ethanol molecules. © 2013 Society of Chemical Industry