Showing papers on "Permeation published in 1971"
Esso1
TL;DR: In this article, a novel separation technique based on the selectivity of a liquid membrane composed of surfactants and water is described, and the permeation mechanism is discussed in terms of the surfactant concentration, the structure and chain length, the nature of permeate and the solubility of the permeate in water.
Abstract: A novel separation technique based on the selectivity of a liquid membrane composed of surfactants and water is described. The permeation mechanism is discussed in terms of surfactant concentration, surfactant structure and chain length, the nature of permeate, and the solubility of permeate in water.
176 citations
TL;DR: In this paper, the authors measured the permeability of H through iron and steel specimens as a function of compressive and tensile stress, and determined the critical concentration of H to cause embrittlement, calculated on the basis of the interaction energy.
150 citations
TL;DR: Evaluation of the results of this and the preceding paper suggests the following: that cations permeate gallbladder epithelium via channels with fixed neutral sites; that the rate-controlling membrane is thick enough that microscopic electroneutrality must be obeyed.
Abstract: The experimental measurements of passive ion permeation in rabbit gallbladder presented in this paper include: single-salt dilution potentials as a function of concentration gradient; comparison of dilution potentials for different alkali chlorides; comparison of biionic potentials for different alkali chlorides; and biionic mixture potentials as a function of cation concentration gradient. Both dilution potentials and biionic potentials yield the permeability sequence K+>Rb+>Na+>Li+>Cs+, a sequence consistent with simple considerations of ion-site interactions and ion hydration energies. Construction of empirical selectivity isotherms for alkali cation permeation in epithelia shows that permeability ratios are nearer one in the gallbladder and other epithelia than in most other biological membranes, indicating a relatively hydrated permeation route. Evaluation of the results of this and the preceding paper suggests the following: that cations permeate gallbladder epithelium via channels with fixed neutral sites; that the rate-controlling membrane is thick enough that microscopic electroneutrality must be obeyed; that virtually all anion conductance is in a shunt which develops with time after dissection; that apparent permeability changes with solution composition are due to the non-ideal activity factorn being less than 1.0; that effects of pH, Ca++, and ionic strength may involve changes in the anion/cation mobility ratio owing to changes in wall charges or dipoles; and that the permeation route may reside in the tight junctions. A similar mechanism may be applicable to cation permeation in other epithelia.
135 citations
TL;DR: The permeability coefficients of a series of amides, ureas, and diols have been measured on red cells of man and dog using the minimum volume method and allow one to infer that lipid-soluble molecules travel through an organized structure within the lipid membrane and come into contact with polar moieties.
Abstract: The permeability coefficients of a series of amides, ureas, and diols have been measured on red cells of man and dog using the minimum volume method of Sha'afi et al. When the molecules are grouped according to their ether-water partition coefficients, k(ether), the behavior of the hydrophilic molecules, with k(ether) less than water, is different from that of the lipophilic molecules, characterized by k(ether) greater than water. The rate of permeation of the hydrophilic molecules through an aqueous pathway is determined by the molar volume, a parameter in which the geometrical measure of molecular volume is modified by hydrogen-bonding ability. This indicates the importance of chemical interactions within the aqueous path. The permeation of the lipophilic molecules is determined in the first instance by k(ether), taken as a measure of the ease with which the molecule can escape from its aqueous environment. Within the membrane, lipophilic permeability is modified both by steric factors and by the formation of hydrogen bonds with membrane components. These data allow one to infer that lipid-soluble molecules travel through an organized structure within the lipid membrane and come into contact with polar moieties.
130 citations
TL;DR: The view that both the lipid bilayers and the biological membranes are penetrated by single fully dehydrated molecules are supported by the finding that a series of different diols did demonstrate practically identical activation energies.
119 citations
Esso1
TL;DR: In this paper, a novel separation technique based on selective permeation through liquid surfactant membrances for hydrocarbon separations is described, and some of the possible process schemes are discussed.
Abstract: A novel separation technique based on selective permeation through liquid surfactant membrances for hydrocarbon separations is described. Some of the possible process schemes are discussed. The permeation and separation mechanism is discussed in terms of the effects of temperature, using glycerol and acetone as membrane additives, solvent-emulsion mixing intensity, and the nature and composition of feed.
113 citations
TL;DR: The data indicate that PCMBS enters the membrane by at least two channels, one sensitive and the other insensitive to SITS, with only the latter leading to the cation-controlling sulfhydryl groups, and suggest that the cATION permeation path involves an aqueous channel in the membrane.
Abstract: The amino-reactive reagent, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS),1 considerably reduces the uptake of the sulfhydryl agent, parachloromercuriphenylsulfonic acid (PCMBS), but does not reduce its effects on cation permeability and on cation transport. These data indicate that PCMBS enters the membrane by at least two channels, one sensitive and the other insensitive to SITS, with only the latter leading to the cation-controlling sulfhydryl groups. Substitution of phosphate or sulfate for chloride results in an inhibition of PCMBS uptake via the SITS-insensitive pathway. These and other data lead to the conclusion that the SITS-sensitive pathway is the predominant one for anion permeation, and the insensitive one for cation permeation. Parachloromercuribenzoate (PCMB), an agent that is more lipid-soluble than PCMBS, penetrates faster but has a smaller effect on cation permeability. Its uptake is less sensitive to SITS. These and other observations suggest that the cation permeation path involves an aqueous channel in the membrane.
109 citations
TL;DR: There was a good agreement between the selectivity sequences obtained by the two methods for the sixteen compounds used in this study, and although the permeability coefficients are directly related to their bulk-phase partition coefficients, the gallbladder behaves as if the membranes controlling selectivity are more hydrophilic than isobutanol.
Abstract: The permeability of the rabbit gallbladder epithelium to nonelectrolytes was determinted by radioactive tracer techniques and by a rapid osmotic procedure. As expected from empirical and theoretical considerations, there was a good agreement between the selectivity sequences obtained by the two methods for the sixteen compounds used in this study. Although the permeability coefficients are directly related to their bulk-phase partition coefficients, the gallbladder behaves as if the membranes controlling selectivatity are more hydrophilic than isobutanol. The relation between permeability coefficients and molecular weight also show that these membranes are less viscous than other single cell membranes. Small polar solutes exhibit lower apparent activiation energies for permeation than larger solutes, and this is taken as support for the view that small polar molecules permeate across this tissue via a polar pathway. Inutin and sucrose permeability coefficients are in the ratio of their free-solution diffusion coefficients, and the apparent surcose activation energy is indistinguishable from that reported for diffusion in aqueous solution. These latter observations may be explained by the presence of a few large “pores” in the epithelium.
109 citations
TL;DR: In this paper, the concept of homogeneous polymer membrane, in which randomly coiled macromolecules pack the solid phase uniformly leaving some unoccupied space as free volume, has been applied in the study of permeability and selectivity of solutes through water (solvent)-swollen polymer membranes.
Abstract: The concept of a homogeneous polymer membrane, in which randomly coiled macromolecules pack the solid phase uniformly leaving some unoccupied space as free volume, has been applied in the study of permeability and selectivity of solutes through water (solvent)-swollen polymer membranes. Using this treatment, it became clear that fundamental principles of permeation through polymer film, i.e., a solution and diffusion mechanism of permeation, is also applicable to these swollen systems. However, the permeability characteristics of highly swollen systems resemble that of porous media due to the presence of the solvent, and the permeability of a swollen system to a solute cannot be characterized by a single permeability coefficient. The permeabilities based on diffusive flux (molecular flow) and on bulk flow of solvent, both of which occur under certain conditions, should be differentiated. Consequently permeability and permselectivity depend on the type of processes or conditions under which permea...
99 citations
Patent•
26 Apr 1971
TL;DR: In this article, a gas-soluble substance is used to increase the permeability of the membrane and thereby enhance the permeation of the gas through the membrane, and a chamber is provided opposite or surrounding the coated membrane and, in accordance with the teachings of the present invention, the chamber may be vented to the atmosphere, evacuated and sealed or communicated to a means for establishing a pressure in the chamber sufficiently lower than the pressure of the liquid exposed to the membrane such that the membrane is enhanced.
Abstract: Apparatus for reducing the dissolved gas concentration in a liquid, for example, a liquid flowing in chromatographic system, utilizing the ability of the gas dissolved in the liquid to pass through a gas permeable membrane. The liquid is exposed to one surface of the membrane and the opposite surface of the membrane is provided with a coating of gas-soluble substance for increasing the permeability of the membrane and thereby enhancing the permeation of the gas through the membrane. Further, in various embodiments of the invention, a chamber is provided opposite or surrounding the coated membrane and, in accordance with the teachings of the present invention, the chamber may be vented to the atmosphere, evacuated and sealed or communicated to a means for establishing a pressure in the chamber sufficiently lower than the pressure of the liquid exposed to the membrane such that the permeation of the gas through the membrane is enhanced. Additionally, the chamber may be provided with absorbent or adsorbent material for accommodating gas permeated through the membrane.
76 citations
TL;DR: The addition of plasticizers generally lowered the water vapor transmission rate, moisture absorption, and water permeation but had little effect on tablet‐disintegration time, and addition of most plasticizers resulted in poorer enteric coating performance.
TL;DR: In this article, it was shown that the ceiling flux in reverse osmosis is equal to the pervaporation flux in highly swollen polymer membranes. But the proposed ceiling flux was not shown to correlate with the permeation flux for such membranes.
Abstract: The pressure-driven transport of liquids employed in reverse osmosis has been shown to occur by a solution-diffusion mechanism in highly swollen polymer membranes A theory based on this mechanism was successfully used earlier to correlate permeation fluxes for such membranes Positive confirmation of this theory is provided here by direct measurement of the proposed concentration gradient A study of the temperature dependence of the liquid diffusion coefficient in the polymer membrane has provided additional evidence of a hydrodynamic regime of diffusion in highly swollen membranes It is also shown that the proposed ceiling flux in reverse osmosis is equal to the pervaporation flux
TL;DR: In this article, sedimentation coefficients have been measured for poly-α-methylstyrene (PAMS) in toluene and in cyclohexane as a function of molecular weight, concentration and temperature.
Abstract: Sedimentation coefficients have been measured for samples of poly-α-methylstyrene (PAMS) in toluene and in cyclohexane as a function of molecular weight, concentration and temperature.
Considering the analogy, at high polymer concentrations, between the sedimentation of a polymer in a solvent and the permeation of solvent through a porous plug of polymer material a general relation, based on irreversible thermodynamics, between the sedimentation coefficient and the permeability, was derived and applied to the measured sedimentation coefficients.
At low temperature, the permeability in cyclohexane (poor solvent) was about three times as high as that in toluene (good solvent). This difference is ascribed to local associations in the poor solvent, because the permeability in the poor solvent decreases strongly as the temperature is raised.
In calculations of the frictional coefficient of polymer coils, permeability has hitherto been an unknown quantity with an adjustable value. The present investigation shows that permeabilities can now be determined direct from sedimentation measurements at finite concentration.
TL;DR: The results suggest that the mechanism of cation permeation in the gallbladder is not the same as that in a macroscopic ion-exchange membrane; that cation mobility ratios are closer to one than are equilibrium-constant ratios; and that the rate-limiting step for cation infiltration is in the membrane interior rather than at the membrane-solution interface.
Abstract: The questions underlying ion permeation mechanisms, the types of experiments available to answer these questions, and the properties of some likely permeation models are examined, as background to experiments designed to characterize the mechanism of alkali cation permeation across rabbit gallbladder epithelium. Conductance is found to increase linearly with bathing-solution salt concentrations up to at least 400MM. In symmetrical solutions of single alkali chloride salts, the conductance sequence is K(+)>Rb(+)>Na(+)>Cs(+)∼Li(+). The current-voltage relation is linear in symmetrical solutions and in the presence of a single-salt concentration gradient up to at least 800 mV. The anion/cation permeability ratio shows little change with concentration up to at least 300MM. Ca(++) reduces alkali chloride single-salt dilution potentials, the magnitude of the effect being interpreted as an inverse measure of cation equilibrium constants. The equilibrium-constant sequence deduced on this basis is K(+)>Rb(+)>Na(+)∼Cs(+)∼Li(+). These results suggest (1) that the mechanism of cation permeation in the gallbladder is not the same as that in a macroscopic ion-exchange membrane; (2) that cation mobility ratios are closer to one than are equilibrium-constant ratios; (3) that the rate-limiting step for cation permeation is in the membrane interior rather than at the membrane-solution interface; and (4) that the rate-controlling membrane is one which is sufficiently thick that it obeys microscopic electroneutrality.
TL;DR: In this paper, the apparent oxygen permeability coefficients of silicone rubber were measured at various membrane thicknesses, temperatures, and concentration levels, and it was found that the apparent permeability increases with increasing membrane thickness and approaches asymptotically to the gas phase permeability.
Abstract: The transport of dissolved oxygen in water through a silicone rubber membrane was studied theoretically and experimentally. The apparent oxygen permeability coefficients of silicone rubber were measured at various membrane thicknesses, temperatures, and concentration levels. The permeation flux was measured under both steady-and unsteady-state conditions. For the first time, the thickness effect of dissolved gas permeation has been studied. It was found that the apparent permeability increases with increasing membrane thickness and approaches asymptotically to the gas phase permeability. A general equation was developed to explain this phenomenon based on the concept of immobile boundary layers. It was also observed that the apparent oxygen permeability increased exponentially with increasing concentration levels in water. The temperature dependency of permeability was of the Arrhenius type.
TL;DR: The results suggest that anion permeation is governed by membrane charges while cation permeations is via some electrically neutral mechanism.
Abstract: The resting membrane of a barnacle muscle fiber is mostly permeable to cations in a solution of pH 7.7 whereas it becomes primarily permeable to anions if the pH is below 4.0. Mechanisms of ion permeation for various monovalent cations and anions were investigated at pH 7.7 and 3.9, respectively. Permeability ratios were obtained from the relationship between the membrane potential and the concentration of the test ions, and ionic conductances from current-voltage relations of the membrane. The permeability sequence for anions (SCN > I > NO3 > Br > ClO3 > Cl > BrO3 > IO3) was different from the conductance sequence for anions (Br, Cl > ClO3, NO3 > SCN). In contrast, the permeability and conductance sequences were identical for cations (K > Rb > Cs > Na > Li). The results suggest that anion permeation is governed by membrane charges while cation permeation is via some electrically neutral mechanism.
TL;DR: In this article, the sorption, permeation and diffusion of water in a series of polyalkylmethacrylates has been studied for a number of temperatures in the range 298-353 K. The results are consistent with significant clustering of the water molecules in the polymer matrix.
Abstract: The sorption, permeation and diffusion of water in a series of polyalkylmethacrylates has been studied for a number of temperatures in the range 298–353 K. In each case the diffusion coefficient decreased as the concentration of sorbed water was increased. The heat and the entropy of dilution decreased with concentration and the activation energy for diffusion increased. Polymethylmethacrylate was the exception in that both the heat of dilution and the activation energy for diffusion were independent of concentration. The results are consistent with significant clustering of the water molecules in the polymer matrix. A comparison is made with a random polycondensation model for the association of water through hydrogen-bond formation.
TL;DR: In this article, a theoretical interpretation for the permeation of binary organic liquid mixtures through polymer films is developed, based on an extension of the free-volume theory for diffusion of organic substances in polymers and taking into account the effect of one component of the mixture on the diffusion of the other component.
Abstract: A theoretical interpretation for the permeation of binary organic liquid mixtures through polymer films is developed. The model is based on an extension of the free-volume theory for diffusion of organic substances in polymers and takes into account the effect of one component of the mixture on the diffusion of the other component. The calculated permeabilities are in reasonable agreement with experimentally measured data.
TL;DR: In this paper, the authors used turbulence promoters (rods with intermittently-spaced rings cemented to them) in the tubes of tubular, cellulose-acetate reverse osmosis membranes.
Abstract: SUMMARY— Flow conditions in tubular, cellulose-acetate reverse osmosis membranes were varied by changing the flow rate and by inserting turbulence promoters (rods with intermittently-spaced rings cemented to them) in the tubes. In general, increasing the flow velocity increased the permeation rate. Turbulence promoters were most effective in increasing permeation rate under conditions that, in their absence, permitted fouling of the membrane surface by macrosolutes from the feed. When the feed contained macrosolutes, increasing the flow velocity or use of turbulence promoters increased retention of lactose and potassium. Modifying the flow conditions to increase turbulence improves performance of reverse osmosis membranes by increasing both permeation rate and retention.
TL;DR: In this paper, the authors compared the performance of cellulose acetate membranes for reverse osmosis of whey and deproteinized whey fractions using two types of celluloses.
Abstract: SUMMARY– Permeation rate, retention, and solute flux during reverse osmosis of whey and whey fractions were compared using two types of cellulose acetate membranes. When the feed solutions contained no molecules larger than lactose, concentration polarization had little influence on performance except at the highest available driving force (applied pressure minus difference between osmotic pressures of the feed and permeate = 37.8 atm). With the more complex feeds (whey and deproteinized whey), both concentration polarization and fouling of the membrane occurred. Concentration polarization decreased both permeation rate and retention. Fouling decreased permeation rate, but its influence on retention was variable and depended principally on the feed, the solute, and the available driving force. Proteins and other macromolecules in whey had a greater influence on performance during reverse osmosis than smaller solute molecules. With whey as feed, maximum permeation rates were achieved at low available driving forces (10-12 atm), and were similar for the two types of membranes (about 1 ml/cm2*sec). Increasing the available driving force increased retention and therefore reduced solute flux. Choice between the two membranes requires a compromise between extent of desalting and loss of lactose in the permeate.
TL;DR: Effects of the nature of two membranes, hydrogen-ion concentration, and some additives on the in vitro permeation of chlorpromazine were examined at 37° employing the diffusion technique and reduction in permeation was rationalized on the basis of the adsorption of the drug on solid surfaces.
TL;DR: In this paper, the mean permeability coefficient of polyethylene membranes has been studied at pressures up to 60 atm and at temperatures between −10° and 60° C. The experimental temperature range encompassed the critical temperature of the last four penetrants.
Abstract: The permeation of He, N2, CH4, C2H6, C2H4, CO2, and N2O through polyethylene membranes has been studied at pressures up to 60 atm and at temperatures between −10° and 60° C. The experimental temperature range encompassed the critical temperature of the last four penetrants. The mean permeability coefficient, P, for C2H6, C2H4, CO2, and N2O exhibited an exponential dependence on pressure at reduced penetrant temperatures below and near unity. This dependence decreased with increasing reduced temperature. The values of P for CH4, which were obtained at reduced temperatures above unity, were essentially constant over the entire pressure range. Finally, the P's for N2 and He, which were measured at the highest reduced temperatures, appeared to decrease slightly with increasing pressure. Possible causes for the observed behavior are discussed, and a new correlation for the pressure dependence of the permeability coefficients is presented. The separation of two different N2O-CO2 mixtures by selective p...
TL;DR: In this paper, the authors measured the permeability of various electrolytes through parchment-supported ferrocyanide membranes of manganese, cobalt, silver, and cadmium.
Abstract: The permeability of various electrolytes through parchment-supported ferrocyanide membranes of manganese, cobalt, silver, and cadmium has been measured at 10, 15, 20, 25, and 30°C. The order of permeability at a given temperature was Cl- > NO3- > CNS- > CH3COO- > SO42- for both monovalent and divalent cations. For any given anion, the cations followed the sequence NH4+ > Li+ > Ba2+ > Ca2+ > Mg2+ > Al3+. This sequence has been correlated with the size of the hydrated ion. Further, the data have been considered from the standpoint of the theory of rate processes and the values for the entropy of activation (ΔS′) have been derived assuming an equilibrium distance of 3 A in the membrane. The values of ΔS′ were all negative and decreased with increasing valence of the ions. This was interpreted to mean electrolyte permeation with partial immobilization in the membrane.
01 Apr 1971
TL;DR: Gel permeation chromatograms are interpreted in terms of V, the peak elution volume, which is characteristic for the size of the solute species, which indicates that if solute association takes place, V may become extensively concentration dependent.
Abstract: Gel permeation chromatograms are interpreted in terms of V, the peak elution volume, which is characteristic for the size of the solute species. If solute association takes place, V may become extensively concentration dependent. To further the understanding of this effect a simple theory, which ignores axial diffusion, has been developed, the model for molecular association being a micellar surfactant in equilibrium with its monomer.
TL;DR: The transport of aqueous urea, glucose, and sucrose through the cellulose membrane, Curophane, is described in terms of permeation and frictional coefficients and the observed flow rates through this very thin membrane are quite high.
Abstract: The transport of aqueous urea, glucose, and sucrose through the cellulose membrane, Curophane, is described in terms of permeation and frictional coefficients. As for other cellulose materials, hydraulic flow for Cuprophane is predominantly of a capillary nature. While Cuprophane is relatively selective, reflecting more of these solutes than most other cellulose membranes, the observed flow rates through this very thin membrane are quite high. These permeation properties for Cuprophane are accommodated by the frictional description of membrane transport. The data are discussed and compared with other available data on related cellulose systems.
01 Nov 1971
TL;DR: In this paper, a study of the permeability coefficients of sulphur dioxide in polyethylene, polyamide (Nylon 11), and polycarbonate at 25 °C and at pressures up to one atmosphere was conducted.
Abstract: Studies were made of the permeation, solution, and diffusion of sulphur dioxide in polyethylene, polyamide (Nylon 11), and polycarbonate at 25 °C and at pressures up to one atmosphere. The steady-state permeability coefficients of sulphur dioxide in all three polymers were pressure-dependent, and the effect of pressure on the solution and diffusion processes, which together govern the overall permeation process, account for the observed relations. Solution and diffusion in the two glassy polymers, polyamide and polycarbonate, were strongly pressure-dependent whereas in polyethylene diffusion was pressure-dependent but solution obeyed Henrys law. The vapour pressure isotherms of the glassy polymers obeyed a modified Langmuir expression suggesting that two concurrent sorption mechanisms were operative, the filling of microvoids within the polymer structures and ordinary Henrys law solution. Kinetic sorption-desorption studies showed that diffusion was “Fickian” in polyethylene and polyamide over the entire pressure range. It was also “Fickian” in polycarbonate at pressures up to approximately 25 cm Hg, but “non-Fickian” at higher levels. For each polymer, diffusion coefficients were determined by steady-state permeation and transient sorption-desorption methods, and the separate methods gave similar values.