Application of poly (amide-<Emphasis Type="Italic">b</Emphasis>-ethylene oxide)/zeolitic imidazolate framework nanocomposite membrane in gas separation

Mixed matrix membranes (MMMs) are gaining increasing interest in academic and industrial research due to their combined, desirable properties of both polymers and organic/inorganic filler as important materials. In this work, synthesized zeolitic imidazolate framework (ZIF-8) suspension (10–50 wt%) was directly incorporated into a [poly (amide-b-ethylene oxide) Pebax^® 1657] matrix in order to improve the gas separation performance of the membrane. Dynamic light scattering (DLS) analysis showed an average diameter of 77.4 nm for the prepared nanoparticles. The transparent membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffractometry (XRD). These indicated excellent dispersion of nanoparticles, which was achieved by ultrasonication before casting the solution. Incorporation of ZIF-8 as filler in the polymer matrix led to improved thermal and mechanical stability of the membranes. This was confirmed by TGA and tensile analyses, indicating good contacts provided at the polymer/filler interfaces. The effect of ZIF-8 loading (up to 50 wt%) on membrane performance was investigated and it showed an optimum loading of 30 %. Single gas (CO₂, N₂ and CH₄) permeation tests revealed rapid, enhanced permeability of the nanocomposite membranes without significant changes in selectivity (compared to those of the pristine polymeric membrane). The permeability increases for CO₂, CH₄ and N₂ in the optimum Pebax^® 1657/ZIF-8 (30 wt%) membrane were found in the stated order as 111, 88 and 99 %. The study revealed that Pebax^® 1657/ZIF-8 membranes displayed better gas permeation properties compared to those of Pebax^® 1657.     

High oxygen permeable Zeolite-4A poly(dimethylsiloxane) membrane for air separation

High oxygen permeability with optimal selectivity of the membrane is required for advancement in air separation membrane technology. Zeolite 4A-PDMS composite membranes were prepared by incorporation of Zeolite 4A nanoscale crystals during the polymerization process of PDMS membrane using toluene and n-heptane solvents, and their oxygen gas permeability and selectivity were explored. Small angle neutron scattering (SANS) technique was further used to study the polymer chain conformation and structure of membranes influenced by Zeolite 4A loading. The intersegmental distance between polymer chains and polymer chain aggregation or clustering were found to be increased on increasing the Zeolite 4A content in the membranes. Increment in the O₂ permeability and O₂/N₂ selectivity were observed for both type of membranes (toluene and n-heptane) with 1 wt% Zeolite 4A loading. The best performance result with O₂/N₂ selectivity of 2.6, and O₂ permeability of 1052 Barrer was exhibited by PDMS/toluene membrane loaded with 1 wt% Zeolite 4A. The PDMS/toluene membranes with 10 wt% Zeolite 4A loading exhibited increased O₂ permeability of 1245 Barrer with a fair O₂/N₂selectivity of ~1.7, while the PDMS/n-heptane membrane with the same loading exhibited excellent O₂ permeability of 6773 Barrer but lesser O₂/N₂ selectivity of ~1.2. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48047.     

Preparation of ZIF-8—Pebax 1657 nanocomposite membranes for n-hexane/nitrogen separation as a representative of gasoline vapour recovery

Gasoline vapour emission is hazardous to both human health and the ecosystem and also results in capital loss, altogether revealing the necessity of its recovery. Some ZIF-8–Pebax flat nanocomposite membranes were fabricated by the method of solution casting and used for gasoline vapour recovery as represented by n-hexane vapour/nitrogen separation. Microporous ZIF-8 nanoparticles were synthesized and characterized by Fourier transform infrared (FTIR) and Brunauer–Emmett–Teller (BET) analysis. BET results revealed specific surface area, total volume, and average pore diameter of 940.8 m² · g⁻¹, 0.36 cm³ · g⁻¹, and 1.54 nm, respectively. Pure nitrogen and n-hexane vapour/nitrogen gas mixture permeabilities were measured through the membranes. There was a decline in both permeation rate and selectivity up to 5.0 wt.% of ZIF-8 loading and the next increment at their higher loadings to considerably more values that the pristine membrane. The maximum n-hexane vapour permeability and selectivity at 10.0 wt.% loading of ZIF-8 nanoparticles, the feed flow rate of 173 mL · min⁻¹, and permeate side pressure of −200 mbar were observed as 280.1 Barrer and 106.7, respectively, revealing 60.0% and 36.9% improvements compared with those of the pristine Pebax membrane. Observed 86%–92% n-hexane vapour recovery approves the successful application of the ZIF-8–Pebax nanocomposite membranes for n-hexane/nitrogen separation. The long-term separation performance of 5.0 wt.% ZIF-8 loaded nanocomposite membrane was improved by 76.5% compared with that of the pristine Pebax membrane.     

Mixed Matrix Silicone and Fluorosilicone/Zeolite 4A Membranes for Ethanol Dehydration by Pervaporation

The ability of homogeneous and mixed matrix membranes prepared using standard silicone rubber, poly(dimethylsiloxane) (PDMS), and fluorosilicone rubber, poly(trifluoropropylmethylsiloxane) (PTFPMS), to dehydrate ethanol by pervaporation was evaluated. Although PDMS is generally considered to be the benchmark hydrophobic membrane material in pervaporation, water/ethanol molar permselectivity of a pure PDMS membrane was found to be 0.89 for a feed containing 80/20 w/w ethanol/water at 50°C, indicating a slight selectivity for water. Fluorinated groups in PTFPMS improved the water-ethanol permselectivity to 1.85, but decreased the water permeability from 9.7 × 10^?12 kmol · m/m² · s · kPa in PDMS to 5.1 × 10^?12 kmol · m/m² · s · kPa (29,000 and 15,200 Barrer, respectively). These water permeabilities are attractive, particularly since the rubbery materials should not experience the steep declines in water permeability observed with most standard dehydration membranes as water concentration in the feed decreases. However, the water selectivity is lower than desired for most applications. Particles of hydrophilic zeolite 4A were loaded into both PDMS and PTFPMS matrices in an effort to boost water selectivity and further improve water permeability. Water-ethanol permselectivities as high as 11.5 and water permeabilities as high as 23.2 × 10^?12 kmol · m/m² · s · kPa were observed for the PTFPMS/zeolite 4A mixed matrix membranes?6 times higher than for the unfilled PTFPMS membrane.     

The Effect of Process Parameters on the Pervaporation of Alcohols through Organophilic Membranes

Abstract

Several organophilic membranes were utilized to selectively permeate ethanol, n-butanol, and t-butanol from dilute aqueous mixtures using pervaporation (PV). Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes were utilized to investigate the effect of temperature, pressure, and start-up/transient time on the separation of aqueous ethanol mixtures. Results indicate optimal ethanol selectivity and flux at the lowest permeate-side pressure. Increased temperature significantly enhanced the productivity of PTMSP, but extended operation of the PTMSP membranes at high temperatures resulted in flux degradation. Two other hydrophobic membranes, poly(dimethyl siloxane) (PDMS) and a poly(methoxy siloxane) (PMS) composite, were used to separate n-butanol and t-butanol from dilute aqueous mixtures. The effect of feed concentration on the flux and selectivity was investigated. Both membranes were found to be more permeable to n-butanol than t-butanol. The PDMS membrane was found to be more effective than the PMS membrane in terms of flux and selectivity. The effect of membrane thickness on water permeation and on organic selectivity was also studied using the PDMS membrane.     

Fabrication of highly permeable PDMS@ZIF-8/PVDF hollow fiber composite membrane in module for ethanol-water separation

The construction of high-performance MOF-based hollow fiber composite membrane (HFCM) modules is a significant, yet challenging task for the biofuel production industry. In this study, a novel approach was taken to fabricate PDMS@ZIF-8/PVDF HFCMs in modules through a facile ZIF-8 self-crystallization synthesis followed by pressure-assisted PDMS infusion for pervaporation ethanol-water separation. The as-prepared HFCMs exhibited an ultrathin separation layer (thickness, 370 ± 35 nm), which was achieved through precise regulation of the ZIF-8 membrane and defect repair by PDMS infusion. Moreover, the strategy utilized in this study resolved the defect issues arising from MOF agglomeration in conventional composite membranes. Impressively, at the optimal packing density, the prepared membrane demonstrated a remarkable ethanol flux (1.11 kg m⁻² h⁻¹) with an PSI value (26.59 kg m⁻² h⁻¹) and showed promising long-term stability for the pervaporation of 5 wt% ethanol aqueous solution at 40°C.     

Effects of simultaneous chemical cross-linking and physical filling on separation performances of PU membranes

The novel modified polyurethane (PU) membranes were prepared by β-cyclodextrin (CD) cross-linking and SiO₂/carbon fiber filler, simultaneously. The structures, thermal stabilities, morphologies, and surface properties were characterized by FTIR, TGA, SEM, and contact angle. The results showed that the addition of inorganic particles increased the thermal stabilities of PU membranes. The modified PU membranes possessed more hydrophobic surfaces than pure PU. In the swelling investigation, PU and its modified membranes were swelled gradually with increasing phenol content in the mixture. The membranes modified by CD cross-linking (PUCD) demonstrated the highest swelling degree. Pervaporation (PV) performances were investigated in the separation of phenol from water. Three kinds of modified membranes obtained better permeability and selectivity than PU membranes. With the feed mixture of 0.5 wt% phenol at 60 °C, the modified PU membrane by CD cross-linking and SiO₂ filler (PUCD-S) obtained the total flux of 5.92 kg μm m^?2 h^?1 which was above doubled that of PU (2.90 kg μm m^?2 h^?1). The modified PU membrane by CD cross-linking and carbon fiber filling (PUCD-C) obtained the separation factor of 51.31 which was nearly tripled that of PU (17.72). The PUCD membranes showed both better permeability and selectivity than the pure PU membranes. The increased phenol content induced an increased separation factor of PUCD and PU, but a decreased selectivity of PUCD-S and PUCD-C. The methods of CD cross-linking and inorganic particle filling were effective to develop the overall separation performances, greatly.     

Preparation of PDMS—Silica Nanocomposite Membranes with Silane Coupling for Recovering Ethanol by Pervaporation

In this article, the composite polydimethylsiloxane (PDMS) membranes supported by cellulose-acetate (CA) microfiltration membrane were successfully prepared by adding nano-fumed silica particles modified with a silane coupling reagent, NH₂-C₃H₆-Si(OC₂H₅)₃. The effects of silica content, feed concentration, and feed temperature on the pervaporation performances of the nano-composite PDMS membranes were investigated for recovering ethanol from aqueous solution by pervaporation. It was found that adding the modified silica particles significantly improved the pervaporation performances of the composite membranes. When the silica content in the membrane was 5 wt%, for a 5 wt% ethanol/water mixture at 40°C, the permeation flux of the membrane maintained about 200 g · m^?2 · h^?1 and separation factor reached the maximum value of 19.     

Pervaporation of Acetaldehyde Aqueous Solution through Zeolite 3A-Polyurethane (PU) Composite Membrane

3A-filled hydrophilic polyurethane (PU) membranes were prepared by incorporating zeolite 3A into PU for pervaporation separation of acetaldehyde and water mixtures (acetaldehyde concentration 2 wt%–20 wt%). The composite membranes were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The morphology and thermal stability of these membranes were also investigated. The effects of zeolite 3A on the sorption, diffusion, and pervaporation performance were evaluated. The swelling study showed that 3A-PU membrane had higher swelling degree in acetaldehyde aqueous solution than in pure water. And the swelling degree of the composite membrane in acetaldehyde solution increased with the 3A content. The permeation flux and water/acetaldehyde separation factor first increased and then decreased with increasing 3A content. The reason may be that a proper quantity of 3A will enlarge the free volume fraction of PU while excessive 3A lead to its poor dispersion. The highest permeation flux of the composite membrane could reach 223 g · m^?2 · h^?1 and the maximum water/acetaldehyde selectivity achieved 7.5. The calculation of sorption selectivity and diffusion selectivity showed that diffusion played a more important role in this process.     

Fabrication of fullerenol-incorporated thin-film nanocomposite forward osmosis membranes for improved desalination performances

Development and use of novel membranes for forward osmosis (FO) applications have gained popularity throughout the world. To enhance FO membrane performance, a novel thin-film nanocomposite membrane was fabricated by interfacial polymerization incorporating Fullerenol (C₆₀(OH)_n) nanomaterial, having n in the range of 24–28 into the active layer. Different concentrations of fullerenol loading (100, 200, 400, and 800 ppm) were added to the top skin layer. The structural and surface properties of the pure thin-film composite membrane (TFC) and fullerenol-incorporated thin-film nanocomposite (FTFC) membranes, were characterized by ATR-FTIR, SEM, and AFM. FO performance and separation properties were evaluated in terms of water flux, reverse salt flux, antifouling propensity, water permeability and salt permeability for all TFC and FTFC membranes. Osmotic performance tests showed that FTFC membranes achieved higher water flux and reverse salt flux selectivity compared with those of TFC membranes. The FTFC membrane with a fullerenol loading of 400 ppm exhibited a water flux of 26.1 L m^?2 h^?1 (LMH), which is 83.03% higher than that of the TFC membrane with a specific reverse salt flux of 0.18 g/L using 1 M sodium chloride draw solution against deionized water in FO mode. The fullerenol incorporation in FTFC membranes also contributed to a decreased fouling propensity.     

Fabrication of zeolitic imidazolate frameworks based mixed matrix membranes and mass transfer properties of C4H6 and N2 in membrane separation

1,3-Butadiene (BD) is a petrochemical-based volatile organic compound, extensively used for the manufacture of synthetic rubber. There is no method reported for its recovery from nitrogen mixture. Herein, for the first time, BD is efficiently recovered by gas separation through facile and novel mixed-metal ZIF-8 based mixed matrix membranes (MMMs). Addition of Ni-ZIF-8 nanoparticles in PDMS matrix, significantly improved the penetrant-membrane interactions and the solution-diffusion properties of BD. Positron annihilation lifetime spectroscopy analysis showed that the well dispersion of Ni-ZIF-8 in PDMS enhanced the free volume of membrane and created efficient continuous paths for BD diffusion. Then, 15 wt% Ni-ZIF-8 MMM exhibited the BD permeance of 323 GPU and the BD/N₂ ideal selectivity of 19.5, which were 60 and 81% higher than pure PDMS membrane, respectively. The simultaneous enhancement of BD permeance and BD/N₂ ideal selectivity indicated that Ni-ZIF-8 was an effective filler applied in MMMs for efficient BD recovery.     

Pebax-based mixed matrix membranes loaded with graphene oxide/core shell ZIF-8@ZIF-67 nanocomposites improved CO2 permeability and selectivity

In order to facilitate CO₂ transport in Pebax-based membranes, graphene oxide (GO)/core shell ZIF-8@ZIF-67 nanocomposites were loaded in Pebax copolymer to improve CO₂ permeability and selectivity. The 0.5 wt% GO doped core shell ZIF-8@ZIF-67, which gave highest CO₂ adsorption capacity of 1.12 mmol/g, was used as nanocomposite. The incorporated GO/core shell ZIF enhanced CO₂ adsorption via unsaturated metal sites (Zn-O or Co-O), because O atoms in GO substituted for N atoms coordinated with Zn and Co single atoms in core shell ZIF-8@ZIF-67. Positron annihilation lifetime spectroscopy indicated that GO-templated core shell ZIF nanocomposites generated extra free volume and provided low-resistance channels to facilitate CO₂ transport. Fourier transform infrared spectroscopy analysis revealed that hydrogen bonds were generated between Pebax polymer chains and GO-templated core shell ZIF which improved swelling resistance and reduced interface defects. Therefore, Pebax-based MMMs loaded with 5 wt% GO/core shell ZIF-8@ZIF-67 exhibited optimum CO₂ permeability (173.2 barrers) and ideal selectivity of CO₂/N₂ (61.9) and CO₂/H₂ (11.6), which were 99.7%, 66.4%, and 20.8% higher than Pebax membranes and surpass Robeson 2008 upper bound. The tensile strength increased by 17.6% to 28.8 MPa and elongation at break increased by 7.61%–554.6% when pure Pebax membranes were incorporated with 2.5 wt% GO/core shell ZIF-8@ZIF-67.     

Regulatable pervaporation performance of Zn-MOFs/polydimethylsiloxane mixed matrix pervaporation membranes

Pervaporation (PV) is an emerging separation technique for liquid mixture. Mixed matrix membranes (MMMs) often demonstrate trade-off relationship between separation factor and flux. In this study, by changing the organic linkers (2-methyl imidazolate, imidazole-2-carboxaldehyde, 2-ethyl imidazolate), ZIF-8, ZIF-90 and MAF-6 were prepared and filled in polydimethylsiloxane (PDMS) membranes for dealcoholization of 5% (mass) n-butanol solution, and the membranes properties and pervaporation performances were adjusted. Compared with the pure PDMS membrane, the addition of ZIF-8 resulted in a 9% increase in flux (1136 g·m^-2·h^-1) and a 22.5% increase in separation factor (28.3), displaying anti-trade-off effect. For the MAF-6/PDMS MMMs (2.0% mass loading), the pervaporation separation index (PSI) and separation factor were 32347 g·m^-2·h^-1 and 58.6 respectively (increased by 34% and 154% in contrast with that of the pure PDMS membrane), and the corresponding permeation flux was 552 g·m^-2·h^-1, presenting great potential in the removal butanol from water. It was deduced that the large aperture size combined with moderate hydrophobicity of metal-organic frameworks (MOFs) favor the concurrent increase in permeability and selectivity.     

Effects of supercritical carbon dioxide treatment conditions on the gas separation properties of polydimethylsiloxane hybrid membrane materials for air purification

A siloxane/polydimethylsiloxane (PDMS) hybrid membrane containing fluorinated side chains was prepared by a convenient and mild sol–gel process and a crosslinking reaction. The effects of the supercritical carbon dioxide (scCO₂) conditions (i.e., treatment temperature, treatment time, and treatment pressure) on the permeation properties of fluorinated PDMS containing hybrid membrane were investigated. The chemical structure, microstructure, and physical performance of the membranes treated before and after were also discussed. The chemical structure of the PDMS membranes did not change with the scCO₂ treatment conditions. The membranes still retained better membrane‐forming abilities, higher permeability, and selectivity than normal PDMS membranes. Compared to those of the membrane with membrane formation after scCO₂ treatment, the oxygen permeability coefficient and oxygen/nitrogen separation factor of the membrane with scCO₂ treatment before membrane formation were higher and were up to 7.11 × 10^?8 cm³ (STP) cm/(cm² s cmHg) and 3.27, respectively. The permeation properties of the hybrid membrane were obviously higher than those of Robeson's upper bound. The high air‐purification performance of the hybrid membrane may have been due to the introduction of fluorine atoms into PDMS membrane, and the increase in free volume resulted from the plasticizing function of the scCO₂ treatment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A quaternized poly(vinyl alcohol)/chitosan composite alkaline polymer electrolyte: preparation and characterization of the membrane

Quaternized poly(vinyl alcohol)/chitosan (QPVA/CS) composite membranes were prepared by solution casting method with AlCl₃·6H₂O aqueous solution as solvent for CS and glutaraldehyde as a crosslinker. The crystalline, thermal and mechanical properties of the QPVA/CS composite membranes were studied by Fourier transform infrared spectroscopy, X-ray diffractometry, differential scanning calorimetry, thermogravimetry and tensile test measurements, respectively. The composite membranes were immersed in potassium hydroxide aqueous solution to form polymer electrolyte membranes. The alkaline uptake, swelling ratio, ion conductivity and methanol permeability of the electrolyte membranes were studied. The experimental results indicated that aluminum chloride hexahydrate (AlCl₃·6H₂O) had a positive effect on the mechanical properties of the QPVA/CS composite membrane. The elongation-at-break of this membrane reached the maximum of 401.0%. The alkaline uptake and swelling ratio of the composite membranes decreased. With the addition of 30 wt% AlCl₃·6H₂O, the composite membrane showed the ion conductivity and methanol permeability of 1.82 × 10^?2 S cm^?1 and 2.17 × 10^?6 cm² s^?1, respectively. These values were higher than those of the membrane with acetic acid as the solvent for CS. The selectivity of the QPVA/CS membrane could reach 8.39 × 10³ S s cm^?3. This study showed that with AlCl₃·6H₂O as the solution for CS, the high performance QPVA/CS composite alkaline polymer electrolyte membrane could be prepared.     

Facilitated propylene transport in mixed matrix membranes containing ZIF-8@Agmim core-shell hybrid material

The ZIF-8@Agmim core-shell hybrid material was synthesized via a favorable post-modification method of ion exchange (PMIE). This infrequent ZIF-8@Agmim core-shell structure maintains a well-integrated pore size that is almost the same as ZIF-8. The similar equilibrium isotherms with ZIF-8 and better kinetic separation toward propylene/propane than ZIF-8 render ZIF-8@Agmim to be an interesting candidate for propylene/propane separation. The core-shell hybrid nanomaterial was further used as nanofillers in the polymer of intrinsic microporosity matrix (PIM-1) for propylene/propane separation. The resultant mixed-matrix membranes (MMMs) exhibited a simultaneous increase in C₃H₆ permeability and C₃H₆/C₃H₈ ideal selectivity compared to pure polymer membrane owing to a synergistic effect of molecular sieving from ZIF-8 and π-complexation of Ag⁺ with propylene. The separation performance of the prepared MMM surpasses the upper bound line of polymer membranes. Furthermore, the hybrid materials possess superb photochemical stability and the corresponding MMMs exhibit excellent anti-aging property and long-term stability.     

Extraction of Tetrahydrofuran and Ethylene Dichloride Solvents from Aqueous Solutions by Pervaporation through Thin Film Composite PDMS Membranes

Thin film composite (TFC) hydrophobic PDMS membrane of 5 µm active layer thickness supported on Polyethersulfone (PES) ultraporous substrate was synthesized and thermally crosslinked for the pervaporation based extraction of organic solvents such as Tetrahydrofuran (THF) and Ethylenedichloride (EDC) for the first time. The study was extended to acetone, ethanol, t-butanol, Iso-butanol, and acetic acid. Membranes were characterized by SEM, TGA, XRD, and FTIR to study the surface and cross-sectional morphology, thermal stability, crystalline nature, and structural properties, respectively. High selectivities of 868, 72, and 31 were observed at organic feed concentrations of 0.68, 3.42, and 9.38 wt% in water with reasonable fluxes of 0.2, 0.16, and 0.31 kg m^?2 h^?1 for EDC, THF and acetone, respectively at a downstream vacuum of 0.5 mmHg. The estimated mass transfer coefficients (MTCs) were found to be 9.11 × 10^?6, 11.77 × 10^?6, and 10.73 × 10^?6 m s^?1 for THF, EDC, and acetone extraction, respectively. The membrane exhibited considerable feasibility for scale-up due to its composite nature with significant potential for extraction of volatile organic solvents present in low concentrations. A comparison with previous values reported in literature revealed higher selectivities for extraction of EDC, THF and acetone using the present membrane.     

Dehydration of C2–C4 alcohol/water mixtures via electrostatically enhanced graphene oxide laminar membranes

The dehydration of alcohol/water mixtures using pervaporation membranes requires less energy than is required by conventional separation technologies. In this paper, we report electrostatically enhanced graphene oxide (GO) membranes for the highly efficient pervaporation dehydration of C₂–C₄ alcohol/water mixtures. Positively charged molecules were introduced as the interlayer of negatively charged GO layers via layer-by-layer assembly, thereby creating an electrostatic attraction that drives the assembly of GO nanosheets into ordered interlayer channels. The effects of the feed temperature, water concentration, and continuous operation on the membrane transport behavior were systematically investigated. In the dehydration of 90 wt% alcohol/water mixtures at 70°C, the membrane exhibited ethanol/water, isopropanol/water, and n-butanol/water fluxes of 2.35, 2.98, and 4.69 kg/(m² hr), respectively, as well as separation factors for the same mixtures of 3,390, 5,790, and 4,680, respectively. This excellent alcohol/water dehydration performance outperforms those of state-of-the-art polymeric membranes and GO-based membranes.     

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     

Sorption and permeation of acetic acid–water mixtures by pervaporation using copolymer membrane

Poly (acrylonitrile‐co‐methyl acrylate) copolymer designated as PANMA was used for making pervaporation membrane. This membrane was used for separation of acetic acid–water mixtures over the concentration range of 80–99.5 wt% acetic acid in water. Interaction parameters based on Flory–Huggins lattice model and engaged species induced clustering (ENSIC) model was used to explain swelling of the membranes. Coupling in sorption was explained in terms of activity coefficient of water and acid in feed and membrane using Flory–Huggins model and also by interpolating ENSIC parameters. Flow coupling in pervaporation was also determined from phenomenological deviation coefficients. Intrinsic membrane properties like partial permeability and membrane selectivity of the solvents were also determined. Diffusion coefficient and plasticization coefficient of the solvents were obtained using a modified solution–diffusion model. The copolymer membrane showed high flux and water selectivity for highly concentrated acid. Thus, at 30°C temperature 1–20 wt% water in feed was concentrated to 82–84 wt% water in permeate and for 0.95 wt% water in feed, the membrane showed thickness normalized flux and water selectivity of 1.71 kg m^?2 h^?1 mμ and 409, respectively. OLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers