Activation Energy For Water Permeation Research Articles

Co-depositing polyvinylamine and dopamine to enhance membrane performance for concentration of KAc solutions via sweeping air pervaporation

Polydopamine (PDA) has been used as a tool for engineering surfaces due to its good adhesive characteristics onto various surfaces and abundant functional groups for further improvement. However, its weak hydrophilicity and long term stability in an alkaline environment were a concern for membrane applications. To address the issues, we proposed to use polyvinylamine (PVAm) as a co-depositant with dopamine to fabricate thin film composite (TFC) membranes in order to take advantage of the covalent bonding between polydopamine (PDA) and PVAm and the adhesive properties of PDA oligomers. The membranes were investigated for concentrating KAc solutions via sweeping air pervapoation. It was shown that both the hydrophilicity and stability of the membrane were improved by incorporating PVAm into the membrane during the coating/deposition process. It was shown that a PVAm content of 20–30 wt% (solvent free basis) in the PVAm/dopamine depositing solution (i.e., PVAm/dopamine ratio in the range of 2:8 to 3:7) was appropriate for fabricating TFC pervaporation membranes for concentrating aqueous KAc concentrations. At a high salt concentration of 70 wt% in the feed solution, the membrane showed a water flux of 1.2–1.4 kg/m2.h and essentially a complete retention of the salt when tested over a period of over 200 h. The membranes were characterized in terms of surface hydrophilicity, permeance and activation energy for water permeation. In addition, the mass growth rate of the membrane skin layer during membrane buildup was determined as well to provide an insight into the general behavior of dopamine adhesion and polymerization in surface engineering.

Concentration of potassium acetate solutions via sweeping gas pervaporation using TFC membranes comprising of a PDA sublayer and PEI/PAA bilayers

• TFC membranes comprising of a PDA sublayer and PEI/PAA bilayers. • Pervaporative concentration of potassium acetate solutions. • Only a sweeping air stream is needed to carry out pervaporation. Thin film composite (TFC) membranes comprising of a self-polymerized dopamine (PDA) sublayer and self-assembled polyethyleneimine/poly(acrylic acid) (PEI/PAA) bilayers were developed to concentrate aqueous potassium acetate (KAc) solutions via sweeping gas pervaporation. To have a closer look into permeation behavior of the membrane, pervaporation with aqueous solutions containing other select salts (KCl, NaAc, NaCl and MgCl 2 ) was also investigated. It was shown that the number of the polyelectrolyte bilayers could be reduced effectively by the use of a PDA sublayer in constructing the composite membranes. It was shown that the TFC membrane with a single PEI/PAA bilayer on top of the PDA sublayer was effective for pervaporative concentration of the salts, and a complete salt retention was achieved for essentially all feed solutions studied. The effects of operating conditions (i.e., temperature and feed concentration) and nature of the salt in the feed solution on the performance of the pervaporative separation were also studied, along with an analysis of activation energy for water permeation and mass transfer resistance of the membrane. It was shown that the membrane permeability to water was affected by the anions of the salts more significantly than the cations. The membrane was found stable in pervaporative concentration of the salt solutions at different concentrations and temperatures.

A graphene oxide membrane with self‐regulated nanochannels for the exceptionally stable bio‐oil dehydration

AbstractThe transport behaviors and nanochannel structures of a graphene oxide (GO) membrane were studied for pervaporation dehydration of bio‐oil with a high acidity and a complex composition. The GO membrane showed an unprecedentedly stable water flux of approximately 0.43 kg m−2 hr−1, with a water content of 97 wt% in the permeate throughout 70 hr of pervaporation testing at 30°C. Both the calculated activation energy for water permeation and X‐ray diffraction characterization results confirmed that the nanochannel structures of the GO membrane were temperature‐ and liquid media‐responsive. The molecular intercalation‐induced self‐regulation of the size of laminar nanochannels in the GO membrane was suggested to be primarily responsible for the significantly reduced membrane fouling and the exceptionally stable pervaporation performance for the GO membrane. The mechanistic insights into the nanochannel structures and antifouling properties would provide important inspiration for the design of novel highly fouling‐resistant membrane materials for practical applications.

Dehydration of acetonitrile using cross-linked sodium alginate membrane containing nano-sized NaA zeolite

Pervaporation (PV) separation of water–acetonitrile mixture using sodium alginate (NaAlg) based mixed matrix membranes (MMM) comprising different amounts of nano NaA zeolite (10, 20 and 30 wt%) is investigated in various concentrations of water and temperatures. The prepared membranes are modified by sulfosuccinic acid (SSA) as a crosslinking agent. NaAlg-NaA/SSA membranes are synthesized by a solution casting technique. The process and membrane performance including separation factor, flux and activation energy of permeation are determined. Results reveal that adding of nano zeolite may lead to an increase in the flux and the separation factor of sodium alginate membrane up to 123 and 169%. In addition, using MMM in dehydration of a feed containing 30 wt% of water shows much better performance than alginate membrane. Furthermore, the activation energy of water permeation through MMM is predicted lower than sodium alginate membrane which reflects the facilitated permeation of water through MMM.

Membrane gas dehydration in a pressure-electric coupled field

A novel membrane gas dehydration process in a pressure-electric coupled field was proposed to enhance water vapor permeation and water/gas separation. An electric potential gradient generated by an asymmetric electric field across the membrane was utilized as an additional driving force for polar molecules (e.g., water) to transport through the membrane. The enhancement in water permeation was evaluated and the improvement in water/gas separation was confirmed. The effects of operating parameters (including voltage gradient, pressure gradient, and operating temperature) on permeation were investigated. The results also showed that the activation energy for water permeation was reduced by the electric field.

Effect of Monoglyceride Structure and Cholesterol Content on Water Permeability of the Droplet Bilayer

The process of water permeation across lipid membranes has significant implications for cellular physiology and homeostasis, and its study may lead to a greater understanding of the relationship between the structure of lipid bilayer and the role that lipid structure plays in water permeation. In this study, we formed a droplet interface bilayer (DIB) by contacting two aqueous droplets together in an immiscible solvent (squalane) containing bilayer-forming surfactant (monoglycerides). Using the DIB model, we present our results on osmotic water permeabilities and activation energy for water permeation of an associated series of unsaturated monoglycerides as the principal component of droplet bilayers, each having the same chain length but differing in the position and number of double bonds, in the absence and presence of a varying concentration of cholesterol. Our findings suggest that the tailgroup structure in a series of monoglyceride bilayers is seen to affect the permeability and activation energy for the water permeation process. Moreover, we have also established the insertion of cholesterol into the droplet bilayer, and have detected its presence via its effect on water permeability. The effect of cholesterol differs depending on the type of monoglyceride. We demonstrate that the DIB can be employed as a convenient model membrane to rapidly explore subtle structural effects on bilayer water permeability.

Alcohol dehydration by pervaporation using a carbon hollow fiber membrane derived from sulfonated poly(phenylene oxide)

The performance of carbon hollow fiber membranes derived from sulfonated poly(phenylene oxide) (SPPO) was investigated with respect to the dehydration of aqueous alcohol solutions. SPPO carbon hollow fiber membranes were prepared by pyrolysis of precursor polymer membranes at 600°C, which possess sufficient membrane flexibility and excellent gas separation performance. In pervaporation tests, SPPO carbon membranes exhibited high flux and high separation factors in the separation of water and larger alcohol molecules, indicating that the main permeation mechanism is molecular sieving. In addition, water permeance was much higher than that of H2, which is similar in size to water, suggesting that surface diffusion occurred. Water adsorption measurements and surface analysis by ESCA indicate the presence of oxygen-containing functional groups on the surface of the carbon membrane as adsorption sites. Increasing the temperature resulted in lower water permeances for water/2-propanol systems, though flux exhibited opposite tendencies. The activation energy for water permeation was negative, supporting the likelihood of adsorption effects. Furthermore, water permeance gradually increased with water concentration. Temperature and concentration did not have much influence on ideal selectivity, and maintained a value over 10000 for the range of conditions investigated.

Separation of aqueous salt solution by pervaporation through hybrid organic–inorganic membrane: Effect of operating conditions

Hybrid polymer-inorganic membranes were prepared by crosslinking poly(vinyl alcohol) (PVA), maleic acid (MA) and silica via an aqueous sol–gel route. Membrane characterisation results revealed silica nanoparticles (< 10 nm) were well dispersed in the polymer matrix and significantly reduced swelling of the membrane. The membranes were tested for pervaporation separation of aqueous salt solution with NaCl concentrations of 0.2–5.0 wt% at temperatures 20–65 °C, feed flowrates 30–150 mL/min and permeate pressures 2–40 Torr. The salt rejection remained high (up to 99.9%) under all operating conditions. A high water flux of 11.7 kg/m 2 h could be achieved at a feed temperature of 65 °C and a vacuum of 6 Torr. The effect of operating conditions on water flux is discussed in relation to diffusion coefficients of water and fundamental transport mechanism through the membrane. The activation energy for water permeation was found to vary from 23.8 to 20.1 kJ/kmol when the salt concentration in the feed was increased from 0.2 to 5.0 wt%.

Titanium Oxide Thin Films Prepared by Plasma Enhanced Atomic Layer Deposition Using Remote Electron Cyclotron Resonance Plasma for Organic Devices Passivation

We examined titanium oxide films and their barrier characteristics. Titanium oxide films were deposited at room temperature with electron cyclotron resonance plasma power of 300 W. We measured the growth rate of the titanium oxide film to be 1.8 Å/cycle. Barrier layers on poly(ether sulfon) (PES) substrates were observed to provide activation energy for water permeation. Activation energy of 12.4 kJ/mol was added by applying a titanium oxide coating with a thickness of 100 nm. The passivation performance of the titanium oxide film was also investigated using organic light-emitting diodes (OLEDs). The relative luminance of a 400-nm-thick-coated OLED device was diminished by 11.6% for 20 h.

Zeolite filled P84 co-polyimide membranes for dehydration of isopropanol through pervaporation process

We have developed zeolite 5A and 13X embedded P84 co-polyimide membranes with enhanced permeability and selectivity for the pervaporation dehydration of isopropanol (IPA). It is found that a higher annealing temperature, i.e., 250 ∘ C is more favorable to improve adhesion between zeolite and polymer phase, and to enhance charge transfer complexes (CTCs) formation. FESEM, DSC and gas permeation results show that zeolite 13X has better compatibility with the matrix polymer than zeolite 5A because of stronger interactions between Na cations in zeolite 13X framework and electron acceptor groups of P84 polyimide. The addition of zeolite into the P84 dense membrane improves water sorption capacity and pervaporation separation performance significantly. Owing to the bigger pore size, larger pore volume, higher sorption capacity and better adhesion, the zeolite 13X incorporated P84 membranes has a much higher permeability than zeolite 5A filled membranes. Interestingly, both have comparably high selectivity possibly because of the effects of chain rigidification and partial pore blockage. The addition of zeolite 13X reduces activation energy for water permeation through the membrane but increases that for IPA permeation. However, the addition of zeolite 5A increases activation energy for both water and IPA permeation. Pervaporation permeability increases with zeolite 13X loading, while the selectivity achieves the maximum at 30 wt% zeolite 13X loading. When the zeolite 13X loading approaches 40 wt%, the adhesion between zeolite and polymer becomes poor and the membrane selectivity declines. A comparison between pervaporation and gas separation results reveals that pervaporation membranes can tolerate a higher degree of interstitial defects than gas separation membranes because of stronger molecular interactions between the feed and the polymer, and the larger molecular size difference between penetrants in the former.

High-resolution measurements of water permeability and solubility in microelectronic-casing made of a hydrophobic polymeric composite

Exposing the composite polymeric casing of integrated circuits (ICs) to water results in miniscule water absorption, followed by its permeation throughout the packaging, and component damage. Studying water penetration and solubility mechanisms in the IC casing is crucial for understanding water-related damage mechanisms and protection against them. The main analytical challenge, hereafter, stems from the need to study miniscule water amounts (<0.5 wt %) capable of penetrating the casing, despite its hydrophobic nature. In this article, a TGA has been employed to study the water uptake kinetics in the casing, and to decipher the related water penetration mechanisms. High-resolution measurements of water adsorption and desorption profiles were performed, followed by calculations of the related activation energies and solubility enthalpies. These data were correlated with a relatively new model that assigned the primary locales of the adsorbed water to the compatible filler–polymer interface. Thus, water permeability is related to molecules hopping between these sites. Finally, we have shown that for the IC casing in our study, the activation energy of water permeation is related to the binding energy of H2O onto the SiOSi groups at the fused-silica-filler surface, where they desorb, hop, and reabsorb. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4523–4527, 2006

Molecular dissection of water and glycerol permeability of the aquaglyceroporin from Plasmodium falciparum by mutational analysis.

The selectivity of aquaporins for water and solutes is determined by pore diameter. Paradoxically, the wider pores of glycerol facilitators restrict water passage by an unknown mechanism. Earlier we characterized an aquaglyceroporin from Plasmodium falciparum with high permeability for both glycerol and water. We use point mutations to demonstrate that amino acids directly lining the pore are not responsible for the excellent water permeability of the Plasmodium aquaglyceroporin but affect permeability of pentitols. Within a conserved WET triad in the extracellular C-loop we identified a Plasmodium aquaglyceroporin-specific glutamate (E125) located in proximity to a conserved arginine (R196) at the pore mouth. Mutation of E125 to serine largely abolished water permeability. Concomitantly, the activation energy for water permeation was increased by 4 kcal/mol. Mutation of the adjacent tryptophan to cysteine led to irreversible inhibition of water passage by Hg(2+). This unequivocally proves the proximity of the couple W124/E125 close to the pore mouth. We conclude that in the Plasmodium aquaglyceroporin the electrostatic environment at the extracellular pore entry regulates water permeability.

Pervaporation, a novel technique for the measurement of vapor transmission rate of highly permeable films

The moisture vapor transmission rate (MVTR) of poly(ether-block-amide) breathable films were measured with a set-up based on the ASTM E96 E and BW methods. These methods led to reliable MVTR for films of low breathability, but not for films of high breathability. The latter shows MVTR values varying over a large range when the operating conditions are changed. An analysis of the mass and the heat transfers pointed out the crucial role of the transfer resistances in the external phases adjacent to the film. The pervaporation technique was designed to minimize these mass and heat transfer resistances using a powerful stirring of the upstream chamber and a good vacuum applied on the downstream chamber. The MVTR was determined from the weight of vapor condensed in a cool trap. The MVTR of films of high breathability were reliably determined by this method; their value was much higher than those obtained with the ASTM E96 BW method for the same films. The obtained intrinsic MVTR data suggest that (i) the film structure is more ordered at lower thickness, and (ii) the activation energy for water permeation is low, probably due to the high flexibility of polyether segments. The technique was successfully used for the measurement of a very high MVTR film made of poly(vinylalcohol), ca. 120 kg day −1 m −2, and for the measurement of the permeation rate of ethylacetate through a silicone rubber film.

Effects of dimethylsulfoxide and mercurial sulfhydryl reagents on water and solute permeability of rat kidney brush border membranes

The effects of dimethylsulfoxide, DMSO, and mercurial sulfhydryl reagents have been studied on water and small solute permeability of rat renal brush border membrane vesicles. Water and solute permeability was measured by mixing membrane vesicles with hypertonic solutions in a stopped-flow apparatus and following osmotically-induced changes in vesicular volume via changes in scattered light intensity. The rate constant of the fast osmotic shrinkage is proportional to the osmotic water permeability, while the rate constant of the slow reswelling phase is proportional to the solute permeability. Using mannitol as the osmotic agent, the osmotic shrinkage of rat renal brush border membrane vesicles followed a biphasic time course. 80% of the vesicles shrunk with a rate constant of approx. 50 s −1 and 20% with a rate constant of approx. 2 s −1, DMSO decreased dose-dependently the amplitude of the fast osmotic shrinkage, without affecting its rate constant. In contrast to DMSO, HgCl 2 decreased the rate constant but not the amplitude of the fast osmotic shrinkage of renal brush border vesicles. Between 40–50 μM HgCl 2, the inhibition of the fast osmotic shrinkage was completed. DMSO and HgCl 2 increase the activation energy of water permeation in renal membranes from 3 to 12–15 kcal/mol. DMSO and HgCl 2 did not affect the rate constant of the slow osmotic shrinkage of renal membrane vesicles and were also without effect on osmotic shrinkage of small intestinal brush border and pure phospholipid vesicles. In renal brush border membranes, HgCl 2 at low concentrations (<10 μM) increased by 15-fold the permeability to NaCl and urea but not to mannitol, an effect which precedes the inhibition of water permeability at higher HgCl 2 concentrations. The increase in small solute permeability was irreversible while the inhibition of water permeability could be reversed with cysteine and dithiothreitol. We conclude that water and small solute pathways in rat renal brush border membranes are completely separate entities, which are effected differently by DMSO and HgCl 2. These pathways for water and solutes must be membrane proteins since neither DMSO nor HgCl 2 affect the permeability properties of pure phospholipid vesicles.

Osmotic water permeability in glycoprotein containing liposomes.

The kinetics of osmotic water permeability in proteoliposomes containing alpha 1-acid glycoprotein was investigated by means of stopped-flow spectrophotometry. A biphasic time-course of scattered light with time was registered. The rate constants calculated from fits to an exponential function in the first phase were proportional to the final medium osmolarity. The apparent second order rate constants Kapp (Osm-1 sec-1) were determined at different glycoprotein concentrations in the original mixture for preparation of proteoliposomes. The value of Kapp at lipid:glycoprotein weight ratio = 1 was plotted in Arrhenius coordinates. The calculated activation energy for water permeation through the lipid bilayer suggests that eventual channel mechanism may be involved due to the presence of glycoprotein molecule in the liposomes.

Osmotic water permeabilities of brush border and basolateral membrane vesicles from rat renal cortex and small intestine.

The osmotic water permeability Pf of brush border (BBM) and basolateral (BLM) membrane vesicles from rat small intestine and renal cortex was studied by means of stopped-flow spectrophotometry. Scattered light intensity was used to follow vesicular volume changes upon osmotic perturbation with hypertonic mannitol solutions. A theoretical analysis of the relationship of scattered light intensity and vesicular volume justified a simple exponential approximation of the change in scattered light intensity. The rate constants extracted from fits to an exponential function were proportional to the final medium osmolarity as predicted by theory. For intestinal membranes, computer analysis of optical responses fitted well with a single-exponential treatment. For renal membranes a double-exponential treatment was needed, implying two distinct vesicle populations. Pf values for BBM and BLM preparations of small intestine were equal and amount to 60 microns/sec. For renal preparations, Pf values amount to 600 microns/sec for the fast component, BBM as well as BLM, and to 50 (BBM) and 99 (BLM) microns/sec for the slow component. The apparent activation energy for water permeation in intestinal membranes was 13.3 +/- 0.6 and in renal membranes 1.0 +/- 0.3 kCal/mole, between 25 and 35 degrees C. The mercurial sulfhydryl reagent pCMBS inhibited completely and reversibly the high Pf value in renal brush border preparations. These observations suggest that in intestinal membranes water moves through the lipid matrix but that in renal plasma membranes water channels may be involved. From the high Pf values of renal membrane vesicles a transcellular water permeability for proximal tubules can be calculated which amounts to approximately 1 cm/sec. This value allows for an entirely transcellular route for water flow during volume reabsorption.

Alcohol effects on rapid kinetics of water transport through lipid membranes and location of the main barrier.

The effect of 1-alkanols (from 1-butanol up to 1-dodecanol) on the water permeability of dimyristoylphosphatidylcholine vesicle membranes was studied by measuring the osmotic swelling rate as functions of 1-alkanol concentrations and temperatures above the gel-to-liquid-crystalline phase transition. For 1-butanol and 1-hexanol, the activation energy for water permeation was invariant with the addition of alkanols, whereas for 1-octanol, 1-decanol and 1-dodecanol, the activation energy decreased depending on the alkanol concentration, and the extent of the decrease was larger for alkanol with a longer hydrocarbon chain. These results suggests that hydrocarbon moiety beyond seven or eight carbon atoms from the head group in phospholipid molecules constitutes the main barrier for water permeation through the dimyristoylphosphatidylcholine vesicle membrane. The relative volume change of the vesicle due to osmotic swelling increased with the addition of 1-alkanols. Presumably, the membrane structural strength is weakened by the presence of 1-alkanols in the membrane. Contrary to the dependence of the swelling rate upon the alkanol carbon-chain length, no significant difference in the effect on the relative volume changes was seen among the 1-alkanols. This result suggests that weakening of the membrane structure is caused by perturbation of the membrane/water interface induced by incorporation of 1-alkanols into the membrane.

The water permeability of the monoolein/triolein bilayer membrane

The water permeability of the lipid bilayer can be used as a probe of membrane structure. A simple model of the bilayer, the liquid hydrocarbon model, views the membrane as a thin slice of bulk hydrocarbon liquid. A previous study (Petersen, D. (1980) Biochim. Biophys. Acta 600, 666–677) showed that this model does not accurately predict the water permeability of the monoolein/ n-hexadecane bilayer: the measured activation energy for water permeation is 50% above the predicted value. From this it was inferred that the hydrocarbon chains in the lipid bilayer are more ordered than in the bulk hydrocarbon liquid. The present study tests the liquid hydrocarbon model for the monoolein/triolein bilayer, which has been shown to contain very little triolein in the plane of the membrane (Waldbillig, R.C. and Szabo, G. (1979) Biochim. Biophys. Acta 557, 295–305). Measurements of the water permeability coefficient of the bilayer are compared with predictions of the liquid hydrocarbon model based on measurements of the water permeability coefficient of bulk 8-heptadecene. The predicted and measured values agree quite closely over the temperature range studied (15–35°C): the predicted activation energy is 11.1±0.2 kcal/mol, whereas the measured activation energy for the bilayer is 9.8±0.7 kcal/mol. This close agreement is in contrast with the monoolein/ n-hexadecane results and suggests that, insofar as water permeation is concerned, the liquid hydrocarbon model quite closely represents the monoolein/triolein bilayer.

Permeability of novikoff hepatoma cells to water and monohydric alcohols

The permeability coefficients of Novikoff hepatoma ascites cell membranes for tritiated water ( 3HHO) and for a homologous series of monohydric alcohols (methanol through hexanol) were deduced from linear diffusion coefficients by means of a series-parallel pathway model (Redwood et al. (1974) J. Gen. Physiol. 64, 706–729). Membrane permeability coefficients for 3HHO at 20, 30 and 37°C were (all X10 −5) 97, 125, and 163 cm · s −1, respectively, and were significantly smaller than the corresponding values for the alcohols tested. In the alcohol series, ethanol had the lowest permeability coefficient 198 · 10 −5 cm · s −1 at 20°C. The apparent activation energy for water permeation was 6.7 ± 1.9 S.E. kcal · mol −1. The apparent membrane diffusion coefficients for the alcohols were a complex function of molecular properties with less diffusional membrane resistance to the alcohols in the middle of the homologous series than would have been expected on the basis of oil-water partitioning or molar volume considerations. The conventional parallel aqueous lipophilic pathway model is not consistent with the present data which can be interpreted by consideration of parallel lipophilic pathways through the Novikoff hepatoma cell membrane.

The effect of gramicidin a on the temperature dependence of water permeation through liposomal membranes prepared from phosphatidylcholines with different chain lengths

The permeation of water through liposomal membranes composed of various saturated phosphatidylcholines plus gramicidin A was studied as a function of temperature. 1. 1. The presence of gramicidin in the liposomal bilayers caused an increase in water permeability. Below the phase transition temperature this effect could be measured quite clearly in all the systems we tested, but the extent of the increase was largely dependent on the length of the hydrocarbon chains. 2. 2. Increasing amounts of gramicidin caused a gradual disappearance of the abrupt change in the rate of water permeation near the gel-liquid crystalline phase transition temperature of dipalmitoyl phosphatidylcholine liposomes. Differential scanning calorimetry analysis of the system containing these relatively small amounts of gramicidin still showed a clear transition from the liquid crystalline to the gel state with only a slight reduction in the enthalpy change. 3. 3. In liposomes composed of dimyristoyl, dipalmitoyl and saturated egg phosphatidylcholine there was a concomitant decrease in the activation energy of water permeation in the presence of gramicidin below and above the phase transition temperature. The activation energy for water permeation through longer chained distearoyl phosphatidylcholine liposomal bilayers was the same with or without gramicidin in the bilayer. 4. 4. It is concluded that the ability of gramicidin to form conducting channels in a gel state bilayer depends on the thickness of the paraffin core.