Showing papers on "Permeation published in 2007"
TL;DR: In this paper, the authors provide a framework for describing the permeability, solubility and diffusivity of hydrogen and its isotopes in austenitic stainless steels at temperatures and high gas pressures of interest for hydrogen storage and distribution infrastructure.
361 citations
TL;DR: In this article, the influence of CO 2 on the oxygen permeation performance of perovskite-type (Ba 0.5 Sr 0.8 Fe 0.2 )O 3− δ (BSCF) membranes under different experimental conditions is presented.
339 citations
TL;DR: In this article, the performance of asymmetric polyethersulfone ultrafiltration flat sheet membranes with polyethylene glycol (PEG) of different molecular weight as additives was reported.
331 citations
TL;DR: In this paper, the authors measured water permeation, desorption, and permeation in and through Nafion 112, 115, 1110 and 1123 membranes as functions of temperature between 30 and 90°C.
305 citations
TL;DR: In this article, the influence of parameters such as transmembrane pressure (TMP), cross-flow velocity (CFV), oil concentration in feed, pH and salt concentration on the separation behaviors were investigated by the measurements of permeate flux, total organic carbon (TOC) removal efficiency, and size and zeta potential of the emulsion droplets.
257 citations
TL;DR: In this article, a highly hydrophobic DDR-type zeolite membrane was prepared on the outer surface of a porous α-alumina tube for CO2/CH4 separation.
Abstract: Using hydrothermal synthesis, a highly hydrophobic DDR-type zeolite membrane was prepared on the outer surface of a porous α-alumina tube. The results of this study show that it is useful for CO2/CH4 separation. Single-gas permeation for CO2, CH4, H2, He, N2, and O2, and CO2/CH4 binary gas permeation, were measured, respectively, at pressures up to 5 and 2 MPa. The respective single-gas permeances of CO2 and CH4 at 298 K at a feed pressure of 0.2 MPa and a permeate pressure of 0.1 MPa were 4.2 × 10-7 and 1.2 × 10-9 mol m-2 s-1 Pa-1; the ideal selectivity for CO2/CH4 was 340. The permeances were in the following order: CO2 > H2 > He > O2 > N2 > CH4. Single-gas permeance was dependent on the relative molecular size of the DDR pore diameter. However, CO2 permeance dominated the adsorption affinity to the pore wall of DDR zeolite. In mixed-gas permeation experiments using the sweep method, the DDR-type zeolite membrane showed high selectivity for CO2/CH4 mixtures of 200 and high CO2 permeance of 3.0 × 10-7 m...
224 citations
TL;DR: Although the central pore of AQP1 is found to be gas permeable, the pure POPE bilayer provides a much larger cross-sectional area, thus exhibiting a much lower free energy barrier for CO2 and O2 permeation, which may only be physiologically relevant in membranes of low gas permeability.
197 citations
TL;DR: In this article, the authors investigated the properties of ( La 0.6 Sr 0.4 ) 0.99 FeO 3 - δ (LSF40) covering thermomechanical properties, oxygen nonstoichiometry and electronic and ionic conductivity.
194 citations
TL;DR: In this paper, a novel nanocomposite membranes (PVA-CNT(CS)) were prepared by incorporating chitosan-wrapped multi-walled carbon nanotube (MWNT) into polyvinyl alcohol (pVA) to further explore the intrinsic correlation between pervaporation performance and free volume characteristics.
191 citations
TL;DR: In this paper, the authors compare theoretical predictions with experimental time lag data obtained for various gases in a model membrane synthesized by dispersing highly adsorptive molecular sieves into silicone rubber.
Abstract: Immobilizing adsorption of diffusing penetrants is known to occur in a number of polymer membrane systems. It will cause very large increases in the diffusion time lag but will have only minor effects on the steady-state permeation. This effect may be troublesome in that considerable errors may be incurred when the time lag method is used to analyze quantitatively the sorption and diffusion behavior in such systems. On the other hand, this effect can be utilized in a beneficial way to design very effective protective coatings, packaging materials, timed release mechanisms, etc. for special situations. The time lag in this case can be predicted very accurately from a theoretical result reported previously. This point is demonstrated here by comparing theoretical predictions with experimental time lag data obtained for various gases in a model membrane synthesized by dispersing highly adsorptive molecular sieves into silicone rubber. The agreement is excellent.
169 citations
TL;DR: In this article, the authors investigated the influence of coupling effects on permeability properties in polydimethylsiloxane (PDMS) at temperatures from −20 to 50°C.
TL;DR: In this article, modified cellulose acetate (CA) ultrafiltration membranes were prepared using Pluronic F127 block copolymer as both pore-forming agent and surface modification agent.
TL;DR: In this paper, the authors show that the rate of the aging effect becomes greater the thinner the film, and the implications of this observation for practical membrane gas separation processes and the selection of membrane materials based on thick film data are discussed.
Abstract: Films made from three glassy polymerspolysulfone, poly(2,6-dimethyl-1,4-phenylene oxide), and a commercial polyimide known as Matrimidwere prepared in thicknesses ranging from 0.4 μm to 60 μm, and their permeabilities to oxygen, nitrogen, and methane were monitored for more than a year. These films exhibited substantial decreases in permeability with time, because of volume relaxation that is due to physical aging, which is a reversible process. The observed permeability coefficients were originally greater than the literature values for thick, or so-called “bulk” films, but eventually decreased well below these values. The rate of the aging effect becomes greater the thinner the film. The implications of this observation for practical membrane gas separation processes and the selection of membrane materials based on thick film data are discussed.
TL;DR: In this paper, the outer surfaces of a hollow fiber were modified to be hydrophobic by grafting with 0.01 mmol/l of 1H, 1H 1H 2H, 2H-perfluorooctylethoxysilane (FAS) solution.
TL;DR: In this article, the surface carboxylation of glutaraldehyde crosslinked chitosan (CS-GA) membrane was successfully achieved by the reaction of amine groups on the CS-GA membrane surface with anhydride groups of maleic anhydrite (MA) in acetone solution.
TL;DR: The powerful permeation enhancing ability of HTM with a suitable viscosity makes it promising alternative carrier for transdermal administration of drug molecule at an extremely low concentration.
TL;DR: This work presents a method for all-atom simulation of electric field-driven transport of large solutes through membrane channels, which in tens of nanoseconds can provide a realistic account of a permeation event that would require a millisecond simulation using conventional MD.
Abstract: The transport of biomolecules across cell boundaries is central to cellular function. While structures of many membrane channels are known, the permeation mechanism is known only for a select few. Molecular dynamics (MD) is a computational method that can provide an accurate description of permeation events at the atomic level, which is required for understanding the transport mechanism. However, due to the relatively short time scales accessible to this method, it is of limited utility. Here, we present a method for all-atom simulation of electric field-driven transport of large solutes through membrane channels, which in tens of nanoseconds can provide a realistic account of a permeation event that would require a millisecond simulation using conventional MD. In this method, the average distribution of the electrostatic potential in a membrane channel under a transmembrane bias of interest is determined first from an all-atom MD simulation. This electrostatic potential, defined on a grid, is subsequently applied to a charged solute to steer its permeation through the membrane channel. We apply this method to investigate permeation of DNA strands, DNA hairpins, and alpha-helical peptides through alpha-hemolysin. To test the accuracy of the method, we computed the relative permeation rates of DNA strands having different sequences and global orientations. The results of the G-SMD simulations were found to be in good agreement in experiment.
TL;DR: In this article, the effects of sintering temperature on the phase structure, oxygen nonstoichiometry, microstructure, electrical conductivity, and oxygen permeation behavior of perovskite La0.6Sr0.4Co0.2Fe0.8O3-delta membranes were systematically studied.
TL;DR: In this article, a novel organic-inorganic hybrid membranes were prepared through sol-gel reaction of polyvinyl alcohol (PVA) with γ-aminopropyl-triethoxysilane (APTEOS) for pervaporation (PV) separation of ethanol/water mixtures.
TL;DR: In this article, a mixture of sericin and polyvinyl alcohol (PVA) was used to produce hydrophilic membranes for alcohol dehydration by pervaporation, which are shown to be preferentially permeable to water.
TL;DR: Both the rate of permeation and potassium transfer significantly increase when hydrophilic surfactants are present and there was no relationship observed between potassium cation transfer from the internal phase and emulsion stability in the storage test.
Abstract: The effects of various commercial and model surfactants of different structure and hydrophilicity were studied on water-in-oil (w/o) emulsion stability, potassium cation leakage and permeation of 6-nitro-3-phenylacetamide benzoic acid in a model system using Penicillin acylase (EC 35111) immobilized in a liquid membrane Both emulsion stability, potassium leakage and permeation of organic substances depend upon hydrophilicity of surfactants Hydrophilic surfactants may be used to stabilize emulsions only in mixtures with hydrophobic emulsifiers Additions of small quantities of hydrophilic surfactants to the system in which permeation occurs together within an enzymatic process may be advantageous Both the rate of permeation and potassium transfer significantly increase when hydrophilic surfactants are present There was no relationship observed between potassium cation transfer from the internal phase and emulsion stability in the storage test
TL;DR: In this paper, it has been shown that CO molecules, remarkably inhibit hydrogen permeation, and that CO minima are much stable than N 2 minima, resulting in a surface effect on the hydrogen penetration through the membrane.
TL;DR: The results for phospholipid membranes in aqueous solution with NaCl and KCl salts show that the formation of transient water pores and the consequent ion leakage can be induced and be driven by a transmembrane ionic charge imbalance, an inherent feature in living cells.
TL;DR: In this article, a surface crosslinked poly(vinyl alcohol) membrane using glutaraldehyde as crosslinking reagent was used for dehydration of ethylene glycol (EG) aqueous solution by pervaporation.
TL;DR: The efficacy of iontophoresis is demonstrated in enhancing the trans-nail delivery of drugs in vitro and it appears that about 50-100 mM ionic strength is required for optimal conduction of electric current across nail.
TL;DR: In this paper, a new hydrogen isotope barrier material, erbium oxide Er2O3, or erbia, has been tested with thermal load test and permeation measurements to determine whether erbia is compatible with other materials at elevated temperatures and if it suppresses hydrogen transport.
TL;DR: The data obtained in this study reveal that the main contribution to the increase in meethanol flux is due to methanol sorption in the membrane.
Abstract: Direct methanol fuel cells (DMFCs) are promising portable power sources. However, their performance diminishes significantly because of high methanol crossover (flux) in the polymer electrolyte membrane (e.g., Nafion 117) at the desired stoichiometric methanol feed concentration. In this study, the diffusion and sorption of methanol and water in Nafion 117 were measured using time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. This technique is unique because of its ability to measure multicomponent diffusion and sorption within a polymer on a molecular level in real time as function of concentration. Both the effective mutual diffusion coefficients and concentrations of methanol and water in Nafion 117 were determined with time-resolved FTIR-ATR spectroscopy as a function of methanol solution concentration. The methanol flux, calculated from FTIR-ATR, matched that determined from a conventional technique (permeation cell) and increased by almost 3 orders of magnitude over the methanol solution concentration range studied (0.1-16 M). Furthermore, the data obtained in this study reveal that the main contribution to the increase in methanol flux is due to methanol sorption in the membrane.
TL;DR: In this paper, an oxygen separation tube with a composite structure in which a dense membrane is formed on a porous body was successfully fabricated using a newly developed mixed conducting oxide, SrCo 0.9 Nb 0.1 O 3− δ (SCN).
TL;DR: In this article, a high reproducible fabrication method for high-flux NaA zeolite membrane has been developed for industrial mass production, and the synthesized NaA membranes exhibited higher water flux (5.6 kgm−m−2h−1) by pervaporation (PV) experiments in a mixture of water (10 ¼ )/ethanol (90 ¼ ).