Separation of greenhouse gases from gas mixtures using nanoporous polymeric membranes

Removal of greenhouse gases from gas streams using porous membranes was carried out in this work. Theoretical studies were performed in terms of mathematical modeling and numerical simulation of CO₂ capture in a flat‐sheet membrane contactor. Numerical simulation was performed using computational fluid dynamics (CFD) of mass and momentum transfer in the membrane module for laminar flow conditions. Physical absorption was considered in the simulations for absorption of CO₂ in pure water. CO₂ concentration distribution in the membrane module was determined through numerical solution of continuity equation coupled with the Navier‐Stokes equations. The modeling predictions indicated that the CO₂ concentration difference is not appreciable in the membrane direction. Moreover, velocity distribution was determined in the liquid side of membrane contactor. CFD also represents a design and optimization tool for membrane gas separation processes. POLYM. ENG. SCI., 55:975–980, 2015. © 2014 Society of Plastics Engineers     

Preparation and gas permeation of composite carbon membranes from poly(phthalazinone ether sulfone ketone)

Composite carbon membranes were prepared from poly(phthalazinone ether sulfone ketone) (PPESK) by incorporating with polyvinylpyrrolidone (PVP) or zeolite (ZSM-5) through stabilization and pyrolysis processes. The thermal stability of composite polymeric membranes was measured by thermal gravimetric analysis. The resultant composite carbon membranes were characterized by scanning electron microscopy, X-ray diffraction and gas permeation technique, respectively. The results illustrated that the thermal stability of composite polymeric membranes was enhanced by addition of ZSM-5 or reduced by PVP. For ZSM-5 or PVP composite carbon membranes prepared at 650 °C, the O₂ permeability is 199.70 Barrer or 124.89 Barrer, and the O₂/N₂ selectivity is 10.3 or 4.2, respectively. Compared with carbon membranes from pure PPESK, the O₂ permeability of ZSM-5 or PVP composite carbon membranes increases by 18.5 or 11.6 times, together with the O₂/N₂ selectivity decreasing by 35.2% or 73.6%, respectively. The gas separation mechanism of composite carbon membranes is molecular sieving. Adsorption effect also plays a significant role for CO₂ permeating through ZSM-5 composite carbon membranes.     

Solvent-resistant polymeric microfiltration membranes based on oxidized electrospun poly(arylene sulfide sulfone) nanofibers

Polymeric membranes have been widely used in the separation of aqueous system, but there were few studies on the organic solvent-resistant microfiltration (MF) membranes. In this study, organic solvent-resistant oxidized poly(arylene sulfide sulfone)-6 (O-PASS-6) nanofibrous MF membrane with high water flux was prepared through electrospun technology, cold-press, and oxidation treatment. The O-PASS-6 nanofibrous MF membrane was made from the interwoven electrospun uniformly 295 nm nanofibers, and the mean pore size was 0.44 μm. The morphology, chemical structure, and aggregation structure of O-PASS-6 nanofibrous MF membrane were characterized systematically by the scanning electron microscope, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Investigations on the weight loss, swelling ratio, and microstructure change all revealed that the O-PASS-6 membrane had superior stability in strong polar solvents, such as 1,3-dimethyl-2-imidazolidinone (DMI), dimethylformamide (DMF), and tetrahydrofuran (THF). MF performance results showed that the pure water flux of O-PASS-6 nanofibrous membrane was up to 753.34 L·m⁻²·h⁻¹, and the rejection ratio was 99.9% to 0.2 μm particles. More importantly, after treated by aggressive solvents, the membranes still possessed good MF performance: the water flux was 770.08, 775.66, and 766.36 L·m⁻²·h⁻¹ when soaked in DMI, DMF, and THF for 7 days, respectively, and high rejection ratio also maintained (>99%) for both particles investigated. The O-PASS-6 membrane with good solvent resistance proved to be a promising candidate as a prefiltration membrane to eliminate submicron particles in both sewage and aggressive solvents. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48506.     

Effect of support layer on gas permeation properties of composite polymeric membranes

PES/Pebax and PEI/Pebax composite membranes were prepared by coating the porous PES and PEI substrate membranes with Pebax-1657. The morphology and performance of the prepared membranes were investigated by SEM and CO₂ and CH₄ permeation tests. The CO₂ permeances of 28 and 52 GPU were achieved for PES/Pebax and PEI/Pebax composite membranes, respectively, with CO₂/CH₄ selectivities almost equal to that of Pebax (26). The experimental data were further subjected to a theoretical analysis using the resistance model. It was found that the porosity and the thickness of the dense section of PES substrate were an order of magnitude higher than those of PEI substitute. The porosity/thickness ratio of PEI substrate was, however, higher than PES, explaining the higher permeance of PEI/Pebax composite membrane. Substrates with porosities much higher than the Henis-Tripodi gas separation membrane were used in this work, aiming to achieve the selectivity of Pebax, rather than those of the substrate membrane materials.     

Separation of gas mixtures using hollow fibre membranes

Conclusions Dependences have been derived for the enrichment of a binary gas mixture with the easily penetrating component on initial concentrations and the stream ratio, and also of specific permeability on the length of the active part of hollow gas-separation fibre.The calculated data agree with experimental data obtained in apparatus employing Graviton hollow fibre in enrichment of air with oxygen.Translated from Khimicheskie Volokna, No. 6, pp. 26–27, November–December, 1988.     

Novel composite polymer electrolyte membranes based on poly(vinyl phosphonic acid) and poly (5‐(methacrylamido)tetrazole)

Heterocyclic molecules are generally used in the proton conducting membranes as dopant or polymer side group due to their high proton transfer ability. Composite proton conducting membranes based on poly(vinylphosphonic acid) (PVPA) and poly(5‐(methacrylamido)tetrazole) (PMTet) were produced. The homopolymers, prepared from their corresponding monomers, were blended at several mol ratios to obtain the polymer electrolyte membranes. All samples were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differantial scanning calorimetry (DSC), cyclic voltammetry (CV), and impedance analysis. Besides, the morphology of the membranes was studied by X‐ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). FTIR spectra confirmed the formation of hydrogen bonding network between PVPA and PMTet units. TGA showed that the polymer electrolyte membranes were thermally stable up to ～210°C. CV curves demonstrated the oxidative stability of the samples in 3 V region. In anhydrous conditions, the maximum proton conductivity was determined as 0.06 Scm^?1 at 150°C for PMTetP(VPA)₄. POLYM. ENG. SCI., 55:260–269, 2015. © 2014 Society of Plastics Engineers     

Characterization of polymeric biocomposite based on poly(vinyl alcohol) and poly(vinyl pyrrolidone)

Biocompatible and easily available materials from dairy production waste were used for modification of water‐soluble polymeric blends of Poly(vinyl alcohol) (PVA) and Poly(vinyl pyrrolidone) (PVP). The resulting biocomposites of PVA/PVP with various concentrations of lactose (L) or calcium lactate (CL) (0, 5, 15, 25, 35 wt%) were prepared by using a solvent cast technique and then characterized by optical microscopy, tensile test, water content determination, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy equipped by attenuated total reflectance device, and also tested for biodegradability. The films were transparent with a smooth surface. The results confirm that L and CL work as fillers in polymeric matrix. The tensile investigations showed enhanced Young's modulus (E) and tensile strength for low‐filled of composite materials (up to 5 wt% L and 15 wt% CL). The biodegradation test in aquatic conditions revealed improved biodegradability of modified blends. Both L and CL seem to be suitable for the modification of polymers, which can be convenient from economical and environmental point of view. POLYM. COMPOS., 27:147–152, 2006. © 2006 Society of Plastics Engineers.     

Theophylline molecular imprint composite membranes prepared from poly(vinylidene fluoride) (PVDF) substrate

Theophylline molecular imprint composite membranes were prepared on the PVDF membrane substrate through the free radical polymerization method using theophylline as a template, methacrylic acid (MAA) as a functional monomer, and ethylene glycol dimethacrylate (EDMA) as a cross-linker. The binding constant (K) for the formation of monomer–template adduct was determined by means of infrared spectroscopy titration and nonlinear least-squares method. Theophylline (K=140 M^?1) can form more specific binding sites with MAA than caffeine (K=83 M^?1), therefore was chosen as the template. An effective ultrasonic cleaning method was used to remove the bound theophylline templates from the polymerized PVDF membrane. The reaction conditions were investigated to optimize the maximum binding capacity of theophylline templates to the PVDF membrane. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and contact angle measurement were used to study the surface chemistry, morphological structure and hydrophilicity of theophylline molecular imprint composite membranes. The specific binding capacities of theophylline imprint membranes were investigated by both single molecule and multi-molecule solution filtration experiments, respectively.     

Preparation and proton conductivity of composite membranes based on sulfonated poly(phenylene oxide) and benzimidazole

The Brønsted acid–base composite membrane was prepared by entrapping benzimidazole in sulfonated poly(phenylene oxide) by tuning the doping ratios. Their thermal stability, dynamic mechanical properties and proton conductivity were investigated under the conditions for intermediate temperature proton exchange membrane (PEM) fuel cell operation. In addition, investigation of activation energies of the SPPO–xBnIm at different relative humidity was also performed. TG–DTA curves reveal these SPPO–xBnIm composite materials had the high thermal stability. The proton conductivity of SPPO–xBnIm composite material increased with the temperature, and the highest proton conductivity of SPPO–xBnIm composite materials was found to be 8.93 × 10⁻⁴ S/cm at 200 °C under 35% relative humidity (RH) with a “doping rate” where x = 2. The SPPO–2BnIm composite membrane show higher storage moduli and loss moduli than SPPO. Tests in a hydrogen–air laboratory cell demonstrate the applicability of SPPO–2BnIm in PEMFCs at intermediate temperature under non-humidified conditions.     

Properties and performance of composite electrolyte membranes based on sulfonated poly(arylenethioethersulfone) and sulfonated polybenzimidazole

A novel composite membranes comprising a sulfonated polyarylenethioethersulfone homopolymer (SPTES-100) and a sulfonated poly(p-phenylene benzobisimidazole) (SPBI), was described in this article. The composite membrane was obtained via a solution cast process in a mixture solvent of N, N-Dimethylacetamide (DMAc) and methanol (MeOH). The proton conductivity of the composite membranes was found to increase with the SPTES-100 content increased. The higher proton conductivity was ∼110 mS/cm at 85 °C and 85% relative humidity for the SPTES/SPBI 70/30 (wt) composite membrane which was considerably less than that of the 300 mS/cm of the SPTES-100 membrane. The mechanical properties indicated that the swelling of the composite membranes was reduced, which is relative to the SPTES-100 polymers, due to the reduced water uptake of the composite membrane by introducing the SPBI into the SPTES polymer matrix. The morphology of the SPTES/SPBI composite membranes was examined by a combination of techniques such as scanning electron microscopy (SEM) and elemental mapping to confirm the dispersion of the SPBI and study the micro-structure of the composite. The membrane electrode assembly (MEA) performance of the composite membranes was preliminary studied for H₂/Air fuel cells applications.     

Pervaporation of chlorinated hydrocarbon-acetone mixtures through poly(ethylene-co-vinyl acetate) membranes

Crosslinked and uncrosslinked ethylene-vinyl acetate copolymer membranes were prepared. The permeation characteristics in the pervaporation process were examined using carbon tetrachloride-acetone mixtures. Modified membranes exhibit carbon tetrachloride permselectivity, but unmodified membranes did not display the permselectivity of crosslinked polymer. Furthermore, membranes modified with dicumyl peroxide (DCP) showed a higher flux and selectivity than those of benzoyl peroxide (BP) modified ones. The effects of feed concentration, molecular size, and polarity of the permeating species on pervaporation were analyzed. The influence of crosslinking density of the membranes on pervaporation was also analyzed. The maximum separation and flux were found to be associated with an optimum amount of crosslinking agent in the membrane. A mixture of chloroform and acetone having a composition near the azeotropic region was also separated by the pervaporation technique. © 1996 John Wiley & Sons, Inc.     

磺化聚苯并咪唑/磺化聚醚砜酸碱复合质子交换膜的制备与表征

为提高膜的尺寸稳定性和阻醇性能,以磺化聚苯并咪唑(S-PBI)与高磺化度聚醚砜(ABPS)两种聚合物为原料,采用溶液共混的方法,制备了系列酸碱复合质子交换膜。研究了复合膜的甲醇溶胀性、吸水率、甲醇渗透系数、质子传导率随S-PBI含量的变化规律。研究表明,随着S-PBI含量的增加,膜的阻醇性能和尺寸稳定性明显提高;同时,复合膜具有较好的质子传导率,有望应用于直接甲醇燃料电池。     

Preparation and properties of poly(acrylic acid) composite membranes

A new type of membrane has been prepared for hyperfiltration (reverse osmosis) desalination that is essentially a very thin polyelectrolyte membrane. It is prepared by casting an aqueous solution of a polyelectrolyte, specifically poly(acrylic acid) (PAA), directly on one surface of a finely porous support membrane. In hyperfiltration tests, these composite membranes exhibit desalination performance comparable in dilute solutions to that observed with cellulose acetate membranes of the Loeb-Sourirajan type. The water flux through these membranes is linear in the pressure up to 100 atm. Salt rejection is a function of pressure; it is also a function of the concentration of the feed solution and the charge of the counterion, in qualitative agreement with the Donnan ion-exclusion mechanism. Typical long-term results range from water fluxes of 2 × 10^?3 g/cm²-sec (50 gal/ft²-day) and 80% salt rejection to 0.2 × 10^?3 g/cm²-sec (5 gal/ft²-day) and >99.5% salt rejection at 1500 psi with 0.3 wt-% NaCl. These membranes appear to be useful for brackish water desalination.     

Preparation and performance testing of sulfonated poly(phenylene oxide) based composite membranes for nanofiltration

Sulfonated brominated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPOBr) was synthesized by a sequence of bromination and sulfonation. A thin film of SPPOBr was coated on top of a commercial poly(ether sulfone) membrane. Pure butoxyethanol (BE) solvent or a BE/isopropyl alcohol (IPA) solvent mixture was used to dissolve SPPOBr in the coating process. The thin film composite membranes so prepared were then tested for the separation of carbohydrate and electrolyte solutes. We found that the flux and the carbohydrate separation both increased significantly with increasing IPA content in the solvent mixture. However, the separation of electrolyte solutes did not change significantly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2624–2628, 2004     

Solid-state structure of melt blended incompatible polymeric mixtures involving poly(vinyl chloride)

Poly(vinyl chlorides) having different melt viscosities were melt blended with several different incompatible polymers using a two-roll mill and a Brabender Plasticorder. The properties of the mixtures can be easily reproduced from batch to batch only if the viscosity of the components does not change during the mixing process. Within this limitation, the order of addition of the components during the mixture preparation does not have a significant influence on the mixture properties. The shear storage modulus of the incompatible mixtures in the temperature range between the Tg's of the components varies with the difference in component viscosities at the temperature of mixing. The moduli of these mixtures are compared to moduli calculated using Kerner's equations. Based on this comparison it is concluded that in any incompatible mixture the component having the lower melt viscosity at the temperature of processing tends to form a continuous phase in the mixture. The greater is the viscosity difference, the greater is this tendency. The viscosity of one component relative to the other can be changed by changing the molecular weight of the components and/or the temperature of mixing.     

Separation of ethylene glycol–water mixtures with composite poly(vinyl alcohol)–polypropylene membranes

Composite membranes consisting of a crosslinked poly(vinyl alcohol)(PVA) active layer on top of a porous polypropylene (PP) support were prepared with glutaraldehyde as a crosslinking reagent. The degree of crosslinking and the thickness of the active layer were determined with attenuated total reflection–Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The membranes were used in the pervaporation dehydration of ethylene glycol (EG)–water mixtures. The effects of the crosslinker content and operational conditions, including feed EG concentration and operating temperature, on the permeation flux and selectivity of the PVA–PP composite membranes were investigated. We observed that the dehydration of a 80 wt % EG mixture at temperature of 60°C, a feed flow rate of 1.5 L/min, and a vacuum pressure of 10 mmHg could be effectively performed, and a moderate permeation flux and a high separation factor were obtained, that is, 0.91 kg m⁻² h⁻¹ and 1021, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Lithium ion conducting polymeric electrolytes based on poly(ethylene adipate)

We report the preparation and properties of polymeric lithium ion conducting films based on poly(ethylene adipate) with lithium trifluoromethanesulfonate and blends of poly(ethylene adipate) and poly(vinyl acetate) with lithium triflouromethanesulfonate.The conductivity/temperature behaviour of these films was found to be very similar to those based on poly(ethylene oxide), with Arrhenius behaviour above the crystalline melting point and slight hysteresis below this temperature.     

Single-ion conducting polymeric electrolytes based on sulfonated poly(phenylene oxide)

In the present paper, the ionic conducting properties of sulfonated poly(phenylene oxide) (PPO) and its alkali-metal salts were investigated in detail. It was found that the material had moderate conductivity, which could reach as high as 10⁻⁶ S/cm at room temperature. Its conductivity dependence on temperature conformed to the Arrhenius equation in a temperature range of 20–90°C. The cation's transference number determined by polarizing reversion was approximately unity. Differential scanning calorimeter, X-ray diffraction, and transmission electron microscope were used to analyze the condensed state structure of the material. © 1997 John Wiley & Sons, Inc.     

Amphiphilic enzyme membranes,I. Preparation of amphiphilic membranes using poly(HEMA) and poly(HEMA-co-st)

Copolymers of 2-hydroxyethyl methacrylate (HEMA) and styrene (St) with various HEMA contents were synthesized in this investigation. Amphiphilic membranes were fabricated by using one layer of hydrophilic poly(HEMA) and one layer of hydrophobic poly(HEMA-co-St) in the presence of a photosensitizer. The oxygen permeability and the water penetration of the amphiphilic membranes with various HEMA contents were estimated. The dependence of the mole fraction of HEMA on hydrophilicity and binding forces on the surface of the amphiphilic membranes were investigated. Characteristics of the amphiphilic membranes on the enzyme immobilization were compared with those of traditional two-layer systems. The response time, stability and pH dependences of the amphiphilic enzyme membrane were also evaluated.     

Pervaporation separation of water–isopropanol mixture using carboxymethylated poly(vinyl alcohol) composite membranes

The pervaporation separation of water–isopropanol mixtures was carried out using carboxymethylated poly(vinyl alcohol) (CMPVA) composite membranes. Carboxymethylated PVA (CMPVA) was synthesized by reacting PVA with various concentrations of monochloroacetic acid. Substitution efficiency of the CMPVA ranged from 12–32%. The cross‐sectional structure of the composite membrane for pervaporation was confirmed by scanning electron microscopy (SEM) exhibiting a 20‐μm active skin layer. Glass transition temperature of the CMPVA was in the range of 74–84°C, and decreased with increasing substitution efficiency. Degree of swelling and permeation flux for water–isopropanol in pervaporation increased with the substitution degree of carboxymethylation. CMPVA composite membrane, having 16% substitution efficiency, showed the following pervaporation performance; permeation flux of 831 g/m² h and separation factor of 362 measured at 80°C and 85 wt % feed isopropanol concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 241–249, 1999