Showing papers on "Permeation published in 1998"
1,105 citations
TL;DR: In this article, the effect of PEG additive as a pore-former on the structure formation of membranes and their permeation properties connected with the changes of thermodynamic and kinetic properties in phase inversion process was investigated.
530 citations
TL;DR: In this article, the physical properties of chitosan and gelatin composite films, plasticized with water or polyols, were studied, and an increase in the total plasticizer content resulted in a considerable decrease of elasticity modulus and tensile strength.
412 citations
TL;DR: In this paper, a thermal treatment of a polyimide Matrimid 5218 was used to stabilize the polymer membrane and showed that the heat treatment clearly suppresses this undesired methane acceleration.
294 citations
TL;DR: In this article, a simple model is presented to describe the permeation of methanol from the anode to the cathode in direct methanoline fuel cell (DMFC).
278 citations
TL;DR: In this article, several different synthesis methods were compared for the preparation of La0.8Sr0.2Co0.6Fe0.4O3−δ powders and coprecipitation method was found most suitable for preparation of the LSCF powder in terms of processibility into dense ceramic membranes.
220 citations
TL;DR: In this article, the crystal orientation of the MFI films was examined using X-ray diffraction pole-figure texture analysis, showing that the crystals were preferentially oriented with both sinusoidal and straight channel networks along directions nearly parallel to the membrane surface.
Abstract: MFI membranes were prepared as free-standing and supported films on porous alumina disks and nonporous substrates. They were synthesized using secondary growth of precursor layers. For self-supported films the first step was to prepare an alumina–silicalite composite film, while for supported films the substrate was first coated with layers of the nanocrystalline silicalite particles. During the following hydrothermal treatment, silicalite particles acting as seed crystals form a dense film, which consists of 0.5–100-μm-thick columnar, intergrown, preferentially oriented grains. The crystal orientation of the MFI films was examined using X-ray diffraction pole-figure texture analysis. The crystals were preferentially oriented with both sinusoidal and straight channel networks along directions nearly parallel to the membrane surface. The degree of orientation increased with increasing membrane thickness. Single gas permeances through thin, oriented membranes were measured. Apparent actiuation energies for permeation were 16, 24, 30, 22 and 26 kj/mol for H2, N2, O2, CH4, and CO2, respectively. Ideal selectivities for H2/N2, CO2/CH4, and O2/N2 were as high as 30, 10, and 3.5, respectively. Binary permeation measurements for the gas pairs CO2/CH4, O2/N2, and CO2/N2 revealed trends similar to those of single gas permeation and the properties are attributed to the membrane microstructure.
191 citations
TL;DR: In this article, a model for multicomponent gas separation using hollow-fiber contactors was developed for simulation of cocurrent, countercurrent, and crossflow contacting patterns with permeate purging (or sweep).
Abstract: A model developed for multicomponent gas separation using hollow-fiber contactors permits simulation of cocurrent, countercurrent, and crossflow contacting patterns with permeate purging (or sweep). The numerical approach proposed permits simulation to much higher stage cuts than previously published work and provides rapid and stable solutions for cases with many components, with widely varying permeability coefficients. This new approach also permits the rational and straightforward incorporation of effects such as permeate sweep, pressure-dependent permeability coefficients, and bore side pressure gradients. Simulation results are presented for separation of commercially significant multicomponent gas mixtures using polymer permeation properties similar to those of polysulfone. The effect of permeate purging on separation performance is explored for air separation. The influence of pressure ratio on hydrogen separation performance for a refinery stream is presented. Air is modeled as a four-component mixture of O2, N2, CO2, and H2O and the refinery stream contains five components: H2, CH4, C2H4, C2H6, and C3H8. In air separation, permeate purging with a small fraction of the residue stream provides a very effective method for improving module efficiency for drying but is not efficient for improving nitrogen purity or recovery. In multicomponent mixtures, maxima in the compositions of components of intermediate permeability may be observed as a function of distance along the hollow fiber. This result suggests the use of membrane staging to capture these components at their maximum concentration.
191 citations
TL;DR: A-type zeolite membranes were synthesized on a porous support tube by a hydrothermal process as discussed by the authors, and the thickness was in the range of 0.4-3.8μm.
188 citations
TL;DR: In this article, an air-gap module with built-in condensing surface was used for conducting experiments on polyvinylidene fluoride flat membrane sheets and the quality of the permeate, quantified by conductivity measurements, and the percolation flux were monitored as the feed temperature, feed flow rate, cooling temperature, and cooling water flow fate were varied.
Abstract: Membrane distillation was investigated as a possible technique for desalination. An air-gap module with built-in Condensing surface was used for conducting experiments on polyvinylidene fluoride flat membrane sheets. The feed stream tested was artificial seawater. The quality of the permeate, quantified by conductivity measurements, and the permeate flux were monitored as the feed temperature, feed flow rate, cooling temperature, and cooling water flow fate were varied. The effect of the distance between the membrane and condensing surface was investigated by adjusting the air gap within the module. A mathematical model incorporating temperature and concentration polarization effects was developed and validated on the experimental data. Good agreement between experimental and predicted values was obtained.
178 citations
TL;DR: In this article, the Wicke-Kallenbach method was applied to a thin (3 μm) zeolite MFI (Silicalite-1) membrane with molecules of different kinetic diameters, d(k).
TL;DR: A fluorometric assay to measure CO2 entry into vesicles concluded that unlike water and small nonelectrolytes, CO2permeation is not significantly altered by lipid bilayer composition or fluidity.
TL;DR: In this article, the authors measured the permeability of polydimethylsiloxane (PDMS) to acetone, nitrogen, and acetone/nitrogen mixtures at 28°C.
Abstract: The permeability of polydimethylsiloxane [PDMS] to acetone, nitrogen, and acetone/nitrogen mixtures has been determined at 28°C. In pure gas experiments, the permeability of PDMS to nitrogen was 245 × 10−10 cm3(STP) · cm/cm2 · s · cmHg and was independent of pressure. The permeability of PDMS to acetone vapor increased exponentially with increasing acetone pressure. PDMS is much more permeable to acetone than to nitrogen; acetone/nitrogen selectivity increases from 85 to 185 as acetone partial pressure in the feed increases from 0 to 67% of saturation. In mixed gas permeation experiments, the nitrogen permeability coefficient is independent of acetone relative pressure and is equal to the pure gas permeability coefficient. The acetone permeability coefficient has the same value in both mixed gas and pure acetone permeation experiments. Average acetone diffusivity in PDMS, determined as the ratio of permeability to solubility, decreases with increasing acetone concentration due to mild clustering of acetone in the polymer (because acetone is a poor solvent for PDMS) and changes in the polymer–penetrant thermodynamic interactions which influence diffusion coefficients. A Zimm–Lundberg analysis of the acetone sorption isotherm is also consistent with acetone clustering in PDMS. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 289–301, 1998
TL;DR: In this article, a tubular module was used to investigate the direct osmosis concentration process in the case of tomato juice and its response to changes of the process parameters was experimentally assessed and established.
TL;DR: Anomalous mole-fraction effects found for permeability ratios and conductance in mixtures of Cl− and SCN− or ClO4 − suggest a multi-ion pore, and hydrophobic interactions with the wall of the channel pore may explain discrepancies between the measured permeabilities of some anions and their size.
Abstract: A distinctive feature of the voltage-dependent chloride channels ClC-0 (the Torpedo electroplaque chloride channel) and ClC-1 (the major skeletal muscle chloride channel) is that chloride acts as a ligand to its own channel, regulating channel opening and so controlling the permeation of its own species. We have now studied the permeation of a number of foreign anions through ClC-1 using voltage-clamp techniques on Xenopus oocytes and Sf9 cells expressing human (hClC-1) or rat (rClC-1) isoforms, respectively. From their effect on channel gating, the anions presented in this paper can be divided into three groups: impermeant or poorly permeant anions that can not replace Cl- as a channel opener and do not block the channel appreciably (glutamate, gluconate, HCO3-, BrO3-); impermeant anions that can open the channel and show significant block (methanesulfonate, cyclamate); and permeant anions that replace Cl- at the regulatory binding site but impair Cl- passage through the channel pore (Br-, NO3-, ClO3-, I-, ClO4-, SCN-). The permeability sequence for rClC-1, SCN- approximately ClO4- > Cl- > Br- > NO3- approximately ClO3- > I- >> BrO3- > HCO3- >> methanesulfonate approximately cyclamate approximately glutamate, was different from the sequence determined for blocking potency and ability to shift the Popen curve, SCN- approximately ClO4- > I- > NO3- approximately ClO3- approximately methanesulfonate > Br- > cyclamate > BrO3- > HCO3- > glutamate, implying that the regulatory binding site that opens the channel is different from the selectivity center and situated closer to the external side. Channel block by foreign anions is voltage dependent and can be entirely accounted for by reduction in single channel conductance. Minimum pore diameter was estimated to be approximately 4.5 A. Anomalous mole-fraction effects found for permeability ratios and conductance in mixtures of Cl- and SCN- or ClO4- suggest a multi-ion pore. Hydrophobic interactions with the wall of the channel pore may explain discrepancies between the measured permeabilities of some anions and their size.
TL;DR: In this paper, a photoimmobilization of poly(N-isopropylacrylamide), photoreactive azidophenyl group was connected to the polymer either at a chain terminal or in side chains.
Abstract: Permeation through a porous polycarbonate membrane, on which a thermosensitive polymer, poly(N-isopropylacrylamide), was immobilized, was investigated For photoimmobilization of poly(N-isopropylacrylamide), photoreactive azidophenyl group was connected to the polymer either at a chain terminal or in side chains The two types of derivatized polymers had different lower critical solution temperature (LCST) Prescribed amounts of the derivatized polymer were cast on the polycarbonate membrane and photoirradiated When a small amount of polymer was used, a thin layer of immobilized polymer was not enough to cover pores of the polycarbonate membrane, while a thick gel layer of immobilized polymer was formed on the polycarbonate membrane to cover pores when a large amount of polymer was used The former is represented by “porous membrane”, and the latter by “nonporous membrane” The rate of water permeation through the porous membranes changed at different temperatures, although permeation through nonimmobili
TL;DR: The morphology and gas permeation properties of montmorillonite−polyelectrolyte self-assembled multilayer systems have been investigated in this paper by means of layer-by-layer deposition.
Abstract: The morphology and gas permeation properties of montmorillonite−polyelectrolyte self-assembled multilayer systems have been investigated. Without any special pretreatment, a stable film of montmorillonite−polymer composite was assembled on a hydrophobic poly(ethyleneterephthalate) support by means of layer-by-layer deposition. All individual alumosilicate platelets were found to be oriented in parallel to the substrate, while their surface density strongly depended on the nature of the polyelectrolyte (charge and molecular weight). The organic−inorganic films were found to be very flexible and crack-resistant even under a considerable mechanical stress. This opened a possibility to preclude gas diffusion through defects and to design highly selective ultrathin membranes. A permeation rate of oxygen was found to decrease 6.6 times for ca. 200 nm montmorillonite/poly(diallyldimethylammonium) chloride film, while a permeation rate of aqueous vapors did not change at all. This effect was attributed to the dom...
TL;DR: In this paper, two basic separator configurations, open flow separators and screen separators, were studied and the experimental results showed that as the permeate flux increases, the temperature and recirculation rate increase.
TL;DR: In this article, the authors investigated the transport mechanism of ethanol/water mixtures by pervaporation and vapor permeation through silicalite membrane, and the results showed almost the same diffusivity between the single component and mixture feed case.
TL;DR: The dependence of the halide permeability coefficients on bilayer thickness and on ionic size were consistent with permeation of hydrated ions by a solubility-diffusion mechanism rather than through transient pores.
TL;DR: In this paper, the Wicke-Kallenbach method was used to evaluate the performance of zeolite membranes with different experimental configurations, such as the orientation of the composite membrane with respect to the feed side, resulting in quite different permeances.
TL;DR: In this article, a semi-interpenetrating polymer network (s-ipn) formation was used to stabilize a polymer membrane in high-pressure CO2/CH4 separations.
Abstract: CO2-induced plasticization may significantly spoil the membrane performance in high-pressure CO2/CH4 separations. The polymer matrix swells upon sorption of CO2, which accelerates the permeation of CH4. The polymer membrane looses its selectivity. To make membranes attractive for, for example, natural gas upgrading, plasticization should be minimized. In this article we study a polymer membrane stabilization by a semiinterpenetrating polymer network (s-ipn) formation. For this purpose, the polyimide Matrimid 5218 is blended with the oligomer Thermid FA-700 and subsequently heat treated at 265°C. Homogeneous films are prepared with different Matrimid/Thermid ratios and different curing times. The stability of the modified membrane is tested with permeation experiments with pure CO2 as well as CO2/CH4 gas mixtures. The original membrane shows a minimum in its permeability vs. pressure curves, but the modified membranes do not indicating suppressed plasticization. Membrane performances for CO2/CH4 gas mixtures showed that the plasticizing effect indeed accelerates the permeation of methane. The modified membrane clearly shows suppression of the undesired methane acceleration. It was also found that just blending Matrimid and Thermid was not sufficient to suppress plasticization. The subsequent heat treatment that results in the s-ipn was necessary to obtain a stabilized permeability.
TL;DR: In this paper, a simple model for the dependence of the net surface oxygen exchange flux on the chemical potential drop at the gas-MIEC interface was used to deduce the ambipolar diffusion coefficient D a and the surface exchange rate coefficient k i0 from a dependence of oxygen permeation on the oxygen pressure gradient.
TL;DR: In this paper, a dense Pd/SS composite membrane with good selectivity for hydrogen and thermal stability was prepared by the electroless plating technique combined with osmosis.
TL;DR: In this article, a temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), was grafted onto porous polyethylene (PE) membranes by UV irradiation and a wide range of graft yields were achieved by varying irradiation time (20-240 min) and monomer concentration (1.2-3.6 wt %).
Abstract: Grafting a temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), onto porous polyethylene (PE) membranes by UV irradiation was investigated. A wide range of graft yields (5–449%) was achieved by varying irradiation time (20–240 min) and monomer concentration (1.2–3.6 wt %). Characterization by XPS and SEM shows that the graft polymers are located both on the external surfaces as well as inside the pores of the membranes. Diffusional permeation experiments show that two distinct types of temperature responses were observed, depending on the graft yield; permeability increases with temperature in low graft yield membranes, while permeability decreases with temperature in high graft yield membranes. A mechanism explaining the dual valve functions of the graft membrane is proposed based on the location of the graft polymers on the membrane. It was also observed the permeability response exhibits a maximum with permeant molecular weight. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2133–2142, 1998
TL;DR: Composite membranes with ultrathin separation layer were prepared by alternating electrostatic adsorption of cationic and anionic compounds at porous supporting membranes such as Celgard 2400, PAN/PET (a polyethyleneterephthalate fleece coated with a thin layer of polyacrylonitrile) and Isopore (an etched ion-track polycarbonate membrane).
TL;DR: Ethylcellulose-polyvinyl pyrrolidone films containing diltiazem hydrochloride and indomethacin should be selected for the development of transdermal drug delivery systems, using a suitable adhesive layer and backing membrane, for potential therapeutic use.
Abstract: Ethylcellulose-polyvinyl pyrrolidone films containing diltiazem hydrochloride and indomethacin were evaluated for their potential drug delivery at a controlled rate, using rat skin, to select a suitable formulation for the development of transdermal drug delivery systems. The influence of film composition, initial drug concentration, and film thickness on the in vitro drug release rate as well as drug permeation through rat abdominal skin were studied. Drug release studies were carried out employing the paddle over disk method and drug permeation through full thickness of the rat abdominal skin was tested using a modified Franz diffusion cell fastened with O-ring. The drug content of the film decreased at an apparent first-order rate, whereas the quantity of drug released was proportional to the square root of time. The release rates of both drugs increased linearly with increasing drug concentration and polyvinyl pyrrolidone fraction in the film, but was found to be independent of film thickness. The increase in release rate may be due to leaching of hydrophilic fraction of the film former which resulted in the formation of pores. It was also observed that the release of drugs from the films followed a diffusion-controlled model at low drug concentrations. A burst effect was observed initially, however, at high drug loading levels. This may be due to rapid dissolution of the surface drug followed by the diffusion of drug through the polymer network in the film. The in vitro skin permeation profiles showed increased flux values with increase of initial drug concentration in the film and also with the concentration of polyvinyl pyrrolidone. From this study, it is concluded that the films composed of ethylcellulose:polyvinyl pyrrolidone:diltiazem hydrochloride (8:2:2) and ethylcellulose:polyvinyl pyrrolidone:indomethacin (8:2:3) should be selected for the development of transdermal drug delivery systems, using a suitable adhesive layer and backing membrane, for potential therapeutic use.
TL;DR: In this article, the influence of membrane thickness on gas permeability and incorporation of cations on water content and ac specific resistance of Flemion® and Nafion®117 were estimated.
TL;DR: In this article, the effect of polyethyleneglycol (PEG) on gas permeabilities and selectivities was investigated in a series of miscible cellulose acetate (CA) blend membranes.
TL;DR: In this article, the authors demonstrate a new principle for separation of linear and branched (2-methyl)alkanes, in the five to seven carbon atom range, by means of permeation through a silicalite membrane.
Abstract: In this paper we demonstrate a new principle for separation of linear and branched (2-methyl)alkanes, in the five to seven carbon atom range, by means of permeation through a silicalite membrane. The permeation selectivity relies on subtle interplay between sorption and diffusion. The required sorption isotherms for the pure components and mixtures are generated using configurational-bias Monte Carlo (CBMC) simulations. The CBMC simulations of the mixture isotherm show a curious maximum in the loading of 2-methyl alkane; this loading decreases to almost zero with increased pressures. The high sorption selectivity for the linear alkane is due to entropic effects; the linear alkane has a higher “packing” efficiency than the branched alkane within the zeolite structure. Calculations for a 50−50 mixture of n-hexane (n-C6) and 2-methylpentane (2MP), for example, show that the higher sorption selectivity for the linear alkane has the effect of enhancing the flux of n-C6 through the silicalite membrane by up to ...