Transport of Gases in Porous Membranes

MRS Bulletin ◽  
1999 ◽  
Vol 24 (3) ◽  
pp. 41-45 ◽  
Author(s):  
Stratis V. Sotirchos ◽  
Vasilis N. Burganos
Keyword(s):  
Pore Space ◽  
Chemical Species ◽  
Molecular Size ◽  
Porous Membrane ◽  
Transport Processes ◽  
Porous Membranes ◽  
Gaseous Species ◽  
Interior Space ◽  
Separation Processes ◽  
Membrane Pore

The capability of membranes to affect differently, both qualitatively and quantitatively, the transport rates of chemical species of dissimilar chemical structure through their interior space renders them attractive for use in many separation problems. Extensive research efforts have thus been undertaken on the preparation and characterization of membrane materials and the study of the transport processes involved in their use in separation applications. The study of the transport of gaseous species through the pore space of porous membranes and the analysis and understanding of the mechanisms that are involved in this process are a very important, if not the most important, element in the development of membranebased separation processes.The resistance that a gaseous species encounters as it is transported through the pore space of a porous membrane is a function of its molecular properties, of its interaction with the material that makes up the walls of the pores, and of the membrane pore structure. Gaseous transport in pores can take place through various mechanisms, whose contribution to the overall transport rate of a particular species is, in general, determined by the strength of the interactions of the molecules of that species with the pore walls and by the relative magnitudes of three length scales that characterize the molecular size, the distance between pore walls, and the density of the fluid in the pore space.

scholarly journals Effect of moisture condensation on vapour transmission through porous membranes

2021 ◽  
pp. 152808372110142
Author(s):  
Ariana Khakpour ◽  
Michael Gibbons ◽  
Sanjeev Chandra
Keyword(s):  
Water Vapour ◽  
Moisture Diffusion ◽  
Porous Membrane ◽  
Water Evaporation ◽  
Porous Membranes ◽  
Water Vapour Concentration ◽  
Vapour Concentration ◽  
Vapour Diffusion ◽  
Pore Blockage ◽  
The Impact

Porous membranes find natural application in various fields and industries. Water condensation on membranes can block pores, reduce vapour transmissibility, and diminish the porous membranes' performance. This research investigates the rate of water vapour transmission through microporous nylon and nanofibrous Gore-Tex membranes. Testing consisted of placing the membrane at the intersection of two chambers with varied initial humidity conditions. One compartment is initially set to a high ([Formula: see text]water vapour concentration and the other low ([Formula: see text], with changes in humidity recorded as a function of time. The impact of pore blockage was explored by pre-wetting the membranes with water or interposing glycerine onto the membrane pores before testing. Pore blockage was measured using image analysis for the nylon membrane. The mass flow rate of water vapour ( ṁv) diffusing through a porous membrane is proportional to both its area (A) and the difference in vapour concentration across its two faces ([Formula: see text], such that [Formula: see text] where K is defined as the moisture diffusion coefficient. Correlations are presented for the variation of K as a function of [Formula: see text]. Liquid contamination on the porous membrane has been shown to reduce the moisture diffusion rate through the membrane due to pore blockage and the subsequent reduced open area available for vapour diffusion. Water evaporation from the membrane's surface was observed to add to the mass of vapour diffusing through the membrane. A model was developed to predict the effect of membrane wetting on vapour diffusion and showed good agreement with experimental data.

A finite element model for predicting the distribution of drugs delivered intracranially to the brain

1997 ◽  
Vol 273 (5) ◽  
pp. R1810-R1821 ◽  
Author(s):  
S. Kalyanasundaram ◽  
V. D. Calhoun ◽  
K. W. Leong
Keyword(s):  
Drug Delivery ◽  
Finite Element ◽  
Spin Echo ◽  
Interleukin 2 ◽  
Chemical Species ◽  
Transport Processes ◽  
Proton Density ◽  
Clear Understanding ◽  
Tissue Properties ◽  
The Brain

Drug therapy to the central nervous system is complicated by the presence of the blood-brain barrier. The development of new drug delivery techniques to overcome this obstacle will be aided by a clear understanding of the transport processes in the brain. A rigorous theoretical framework of the transport of drugs delivered locally to the parenchyma has been developed using the finite element method. Magnetic resonance imaging has been used to track the transport of paramagnetic contrast markers in the brain. The information obtained by postprocessing spin-echo, T1-weighted, and proton density images has been used to refine the mathematical model that includes realistic brain geometry and salient anatomic features and allows for two-dimensional transport of chemical species, including both diffusive and convective contributions. In addition, the effects of regional differences in tissue properties, ventricular boundary, and edema on the transport have been considered. The model has been used to predict transport of interleukin-2 in the brain and study the major determinants of transport, at both early and late times after drug delivery.

scholarly journals Combined Ligand and Structure Based Approaches Towards Developing Novel Renin Inhibitors for the Treatment of Hypertension

2021 ◽  
Author(s):  
P Ambili Unni ◽  
S Sajitha Lulu ◽  
Girinath G Pillai
Keyword(s):  
Chemical Space ◽  
Binding Free Energy ◽  
Chemical Species ◽  
Molecular Size ◽  
Central Component ◽  
Geriatric Population ◽  
Structure Based Drug Design ◽  
Renin Inhibitors ◽  
Treatment Of Hypertension ◽  
Renin Inhibition

<p>Hypertension is considered as the predominant risk factor for the onset of Cardiovascular disease (CVD) in the elder population. The chronic activation of Renin Angiotensin System (RAS) is considered as the primary causative factor for the inception of hypertension in geriatric population. Angiotensin Converting Enzyme (ACE) is a highly explored druggable target in the context of hypertension since this enzyme catalyses the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. But clinical trials conducted on ACE inhibitors reported their incompetence in the effective treatment of hypertension. Hence, recent studies are focussing on renin, which is a central component of RAS in the regulation of blood pressure. The present study focuses on the elucidation of physicochemical properties of chemical compounds essential for renin inhibition and identification of novel renin inhibitors possessing enhanced potency as well as bioavailability. We have employed Molecular Field Topology Analysis (MFTA) as well as Structure Based Drug Design (SBDD) approaches for the accomplishment of above-mentioned objectives. MFTA approach were piloted on 45 indole-3-carboxamide derivatives by elucidating the significance of charge distribution as well as molecular size of chemical species in eliciting renin inhibition. Optimal model was obtained with Nf = 3, r<sup>2 </sup>= 0.81 , Q<sup>2</sup> = 0.65. Molecular docking, atom-based binding free energy contributions and bioavailability assessments were carried out to identify most potent lead molecule among 45 compounds reported for renin inhibition. Further, new derivative molecules were predicted for the best lead molecule by employing chemical space exploration. All datasets, descriptor values, QSAR models for predictions usage and plots will be available in <a href="https://github.com/giribio/agingdata">https://github.com/giribio/agingdata</a></p><p></p>

scholarly journals Scale effect in a fluid-conducting fault network

2019 ◽  
Vol 61 (4) ◽  
pp. 3-14
Author(s):  
V. A. Petrov ◽  
M. Lespinasse ◽  
V. V. Poluektov ◽  
S. A. Ustinov ◽  
V. A. Minaev
Keyword(s):  
Pore Space ◽  
Three Dimensional ◽  
Transport Processes ◽  
Geometrical Parameters ◽  
Fluid Filtration ◽  
Ore Formation ◽  
Fracture Systems ◽  
Eastern Transbaikalia ◽  
Scale Levels ◽  
Fault Network

The data presented in the article consistently outlines the methodology for studying the orientation and morphogenetic characteristics of fracture systems of four scale levels including kilometers, meters, centimeters and millimeters. The Urtuisky granite massif, located in the South-Eastern Transbaikalia to the west of the Streltsovsky caldera, containing uranium deposits unique in their reserves was chosen as the object of the research. The massif is composed of Late Riphean granites and granite-gneisses, affected by dynamometamorphic and hydrothermal-metasomatic transformations in various degrees, and dissected by numerous faults with traces of fluid activity of various tectogenesis episodes. The interrelation between such geometrical parameters of fractures systems as specific density and specific length was established. It is shown that such geostructural data should be used for conceptual and numerical modeling of fluid filtration and radionuclides transport processes occurring in a three-dimensional fractured-pore space of crystalline rocks, as applied to the reconstruction and modeling of uranium ore formation and use of geological space for radioactive materials isolation.

scholarly journals Transport Simulations on Scanning Transmission Electron Microscope Images of Nanoporous Shale

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6665
Author(s):  
Laura Frouté ◽  
Yuhang Wang ◽  
Jesse McKinzie ◽  
Saman Aryana ◽  
Anthony Kovscek
Keyword(s):  
Gas Permeability ◽  
Pore Space ◽  
Knudsen Diffusion ◽  
Transport Processes ◽  
Pore Scale ◽  
Pore Networks ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Stem Tomography

Digital rock physics is an often-mentioned approach to better understand and model transport processes occurring in tight nanoporous media including the organic and inorganic matrix of shale. Workflows integrating nanometer-scale image data and pore-scale simulations are relatively undeveloped, however. In this paper, a workflow is demonstrated progressing from sample acquisition and preparation, to image acquisition by Scanning Transmission Electron Microscopy (STEM) tomography, to volumetric reconstruction to pore-space discretization to numerical simulation of pore-scale transport. Key aspects of the workflow include (i) STEM tomography in high angle annular dark field (HAADF) mode to image three-dimensional pore networks in µm-sized samples with nanometer resolution and (ii) lattice Boltzmann method (LBM) simulations to describe gas flow in slip, transitional, and Knudsen diffusion regimes. It is shown that STEM tomography with nanoscale resolution yields excellent representation of the size and connectivity of organic nanopore networks. In turn, pore-scale simulation on such networks contributes to understanding of transport and storage properties of nanoporous shale. Interestingly, flow occurs primarily along pore networks with pore dimensions on the order of tens of nanometers. Smaller pores do not form percolating pathways in the sample volume imaged. Apparent gas permeability in the range of 10−19 to 10−16 m2 is computed.

scholarly journals Modeling of ethylbenzene dehydrogenation in catalytic membrane reactor with porous membrane

2014 ◽  
Vol 2 (1) ◽  
pp. 1-9 ◽  
Author(s):  
E.V. Shelepova ◽  
A.A. Vedyagin ◽  
I.V. Mishakov ◽  
A.S. Noskov
Keyword(s):  
Mathematical Model ◽  
Membrane Reactor ◽  
Ceramic Membrane ◽  
Porous Ceramic ◽  
Porous Membrane ◽  
Membrane Reactors ◽  
Catalytic Membrane ◽  
Catalytic Membrane Reactor ◽  
Membrane Pore ◽  
Ethylbenzene Dehydrogenation

AbstractThe modeling of ethylbenzene dehydrogenation in a catalytic membrane reactor has been carried out for porous membrane by means of two-dimensional, non-isothermal stationary mathematical model. A mathematical model of the catalytic membrane reactor was applied, in order to study the effects of transport properties of the porous membrane on process performance. The performed modeling of the heat and mass transfer processes within the porous membrane, allowed us to estimate the efficiency of its use in membrane reactors, in comparison with a dense membrane (with additional oxidation of the hydrogen in shell side). The use of a porous ceramic membrane was found to cause an increase of the ethylbenzene conversion at 600°C, up to 93 %, while the conversion in the case of conventional reactor was 67%. In this work, we defined the key parameter values of porous membrane (pore diameter and thickness) for ethylbenzene dehydrogenation in catalytic membrane reactor, at which the highest conversion of ethylbenzene and styrene selectivity can be reached.

scholarly journals Contribution of different effluent organic matter fractions to membrane fouling in ultrafiltration of treated domestic wastewater

2012 ◽  
Vol 2 (4) ◽  
pp. 204-209 ◽  
Author(s):  
X. Zheng ◽  
J. P. Croue
Keyword(s):  
Organic Matter ◽  
Membrane Fouling ◽  
Domestic Wastewater ◽  
Molecular Size ◽  
Effluent Organic Matter ◽  
Membrane Pore ◽  
Pore Opening ◽  
Organic Matter Fractions ◽  
Doc Load ◽  
Hydrophobic Acids

In the present work, effluent organic matter (EfOM) in treated domestic wastewater was separated into hydrophobic neutrals, colloids, hydrophobic acids, transphilic acids and neutrals and hydrophilic compounds. Their contribution to dissolved organic carbon (DOC) was identified. Further characterization was conducted with respect to molecular size and hydrophobicity. Each isolated fraction was dosed into salt solution to identify its fouling potential in ultrafiltration (UF) using a hydrophilized polyethersulfone membrane. The results show that each kind of EfOM leads to irreversible fouling. At similar delivered DOC load to the membrane, colloids present the highest fouling effect in terms of both reversible and irreversible fouling. The hydrophobic organics show much lower reversibility than the biopolymers present. However, as they are of much smaller size than the membrane pore opening, they cannot lead to such severe fouling as biopolymers do. In all of the isolated fractions, hydrophilics show the lowest fouling potential. For either colloids or hydrophobic substances, increasing their content in feedwater leads to worse fouling. The co-effect between biopolymers and other EfOM fractions has also been identified as one of the mechanisms contributing to UF fouling in filtering EfOM-containing waters.

scholarly journals Durability and Recoverability of Soft Lithographically Patterned Hydrogel Molds for the Formation of Phase Separation Membranes

Micromachines ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 108
Author(s):  
Asad Asad ◽  
Masoud Rastgar ◽  
Hadi Nazaripoor ◽  
Mohtada Sadrzadeh ◽  
Dan Sameoto
Keyword(s):  
Phase Separation ◽  
Solvent Extraction ◽  
Cold Treatment ◽  
Porous Membranes ◽  
Separation Processes ◽  
Separation Membranes ◽  
Membrane Fabrication ◽  
Phase Separation Process ◽  
Continuous Use ◽  
Recovery Result

Hydrogel-facilitated phase separation (HFPS) has recently been applied to make microstructured porous membranes by modified phase separation processes. In HFPS, a soft lithographically patterned hydrogel mold is used as a water content source that initiates the phase separation process in membrane fabrication. However, after each membrane casting, the hydrogel content changes due to the diffusion of organic solvent into the hydrogel from the original membrane solution. The absorption of solvent into the hydrogel mold limits the continuous use of the mold in repeated membrane casts. In this study, we investigated a simple treatment process for hydrogel mold recovery, consisting of warm and cold treatment steps to provide solvent extraction without changing the hydrogel mold integrity. The best recovery result was 96%, which was obtained by placing the hydrogel in a warm water bath (50 °C) for 10 min followed by immersing in a cold bath (23 °C) for 4 min and finally 4 min drying in air. This recovery was attributed to nearly complete solvent extraction without any deformation of the hydrogel structure. The reusability of hydrogel can assist in the development of a continuous membrane fabrication process using HFPS.

Separation Features in Hydrocarbon Media at Thermobaric Regimes of Petroleum Preparation Devices Functioning

2017 ◽  
Vol 743 ◽  
pp. 373-377
Author(s):  
Eugenii V. Nikolayev ◽  
Sergey N. Kharlamov ◽  
Laura Meucci
Keyword(s):  
Physical Properties ◽  
Gas Phase ◽  
Transport Processes ◽  
Gas Mixture ◽  
Multicomponent Systems ◽  
Composition Change ◽  
Separation Processes ◽  
Exchange Processes ◽  
Temperature And Pressure ◽  
Hydrocarbon Media

In this paper the features of separation processes modelling are analyzed in hydrocarbonic media within the limits of thermodynamics of equilibrium states. Approaches to calculation of phase equilibrium in multicomponent systems are discussed. Regularities and peculiarities of composition change of gas mixture depending on the temperature and pressure are studied. It has been established that there are specific conditions of non-monotonic change of composition with extremums for some separation regimes that significantly influences the physical properties and intensity of exchange processes at the heat-and mass transfer in multicomponent hydrocarbon media. In addition, the details of the behavior of gas phase with changing its thermal and physical properties have been discussed. Also, the calculated distributions of Prandtl, Schmidt and Lewis-Semenov numbers essentially influencing on the intensity of transport processes are considered.

APTES assisted surface heparinization of polylactide porous membranes for improved hemocompatibility

RSC Advances ◽  
2016 ◽  
Vol 6 (48) ◽  
pp. 42684-42692 ◽  
Author(s):  
Jinglong Li ◽  
Fu Liu ◽  
Xuemin Yu ◽  
Ziyang Wu ◽  
Yunze Wang ◽  
...  
Keyword(s):  
Porous Membrane ◽  
Porous Membranes ◽  
Amidation Reaction

The Hep-APTES/PLA was synthesized through the amidation reaction and results showed that surface heparinization significantly improved the hemocompatibility of PLA porous membrane.

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