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Highlighting Thermodynamic Coupling Effects in Alcohol/Water Pervaporation across Polymeric Membranes

[Image: see text] The pervaporation of binary alcohol/water mixtures across polymeric membranes is modeled by combining the Maxwell–Stefan (M-S) diffusion formulation with the Flory–Huggins (F-H) description of sorption equilibrium. The combined M-S/F-H model shows that the flux of each penetrant sp...

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Autor principal: Krishna, Rajamani
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2019
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751729/
https://www.ncbi.nlm.nih.gov/pubmed/31552372
http://dx.doi.org/10.1021/acsomega.9b02255
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author Krishna, Rajamani
author_facet Krishna, Rajamani
author_sort Krishna, Rajamani
collection PubMed
description [Image: see text] The pervaporation of binary alcohol/water mixtures across polymeric membranes is modeled by combining the Maxwell–Stefan (M-S) diffusion formulation with the Flory–Huggins (F-H) description of sorption equilibrium. The combined M-S/F-H model shows that the flux of each penetrant species is coupled to the driving force of its partner penetrant. Two types of coupling contributions can be distinguished: (i) coupling arising out of correlated motions of penetrants in the polymer matrix and (ii) thermodynamic coupling. The focus of this article is on the contribution of thermodynamic coupling, which is quantified by the set of coefficients [Image: see text], where a(i), the activity of species i, is dependent on the volume fractions ϕ(i),ϕ(j), of both penetrants in the polymeric membrane. Detailed analyses of published experimental data for pervaporation of ethanol/water feed mixtures of varying compositions in both hydrophobic (poly(dimethylsiloxane)) and hydrophilic (cellulose acetate, polyimide, and polyvinyl alcohol/polyacrylonitrile composite) membranes show that in all cases, the cross-coefficients Γ(ij) (i ≠ j) are negative and may attain large magnitudes in relation to the diagonal elements Γ(ii). The net result is that the permeation fluxes of each penetrant are suppressed by its partner, resulting in mutual slowing down of permeation fluxes. If thermodynamic coupling effects are ignored, significantly higher fluxes are anticipated than those that are experimentally observed.
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spelling pubmed-67517292019-09-24 Highlighting Thermodynamic Coupling Effects in Alcohol/Water Pervaporation across Polymeric Membranes Krishna, Rajamani ACS Omega [Image: see text] The pervaporation of binary alcohol/water mixtures across polymeric membranes is modeled by combining the Maxwell–Stefan (M-S) diffusion formulation with the Flory–Huggins (F-H) description of sorption equilibrium. The combined M-S/F-H model shows that the flux of each penetrant species is coupled to the driving force of its partner penetrant. Two types of coupling contributions can be distinguished: (i) coupling arising out of correlated motions of penetrants in the polymer matrix and (ii) thermodynamic coupling. The focus of this article is on the contribution of thermodynamic coupling, which is quantified by the set of coefficients [Image: see text], where a(i), the activity of species i, is dependent on the volume fractions ϕ(i),ϕ(j), of both penetrants in the polymeric membrane. Detailed analyses of published experimental data for pervaporation of ethanol/water feed mixtures of varying compositions in both hydrophobic (poly(dimethylsiloxane)) and hydrophilic (cellulose acetate, polyimide, and polyvinyl alcohol/polyacrylonitrile composite) membranes show that in all cases, the cross-coefficients Γ(ij) (i ≠ j) are negative and may attain large magnitudes in relation to the diagonal elements Γ(ii). The net result is that the permeation fluxes of each penetrant are suppressed by its partner, resulting in mutual slowing down of permeation fluxes. If thermodynamic coupling effects are ignored, significantly higher fluxes are anticipated than those that are experimentally observed. American Chemical Society 2019-09-05 /pmc/articles/PMC6751729/ /pubmed/31552372 http://dx.doi.org/10.1021/acsomega.9b02255 Text en Copyright © 2019 American Chemical Society This is an open access article published under a Creative Commons Non-Commercial No Derivative Works (CC-BY-NC-ND) Attribution License (http://pubs.acs.org/page/policy/authorchoice_ccbyncnd_termsofuse.html) , which permits copying and redistribution of the article, and creation of adaptations, all for non-commercial purposes.
spellingShingle Krishna, Rajamani
Highlighting Thermodynamic Coupling Effects in Alcohol/Water Pervaporation across Polymeric Membranes
title Highlighting Thermodynamic Coupling Effects in Alcohol/Water Pervaporation across Polymeric Membranes
title_full Highlighting Thermodynamic Coupling Effects in Alcohol/Water Pervaporation across Polymeric Membranes
title_fullStr Highlighting Thermodynamic Coupling Effects in Alcohol/Water Pervaporation across Polymeric Membranes
title_full_unstemmed Highlighting Thermodynamic Coupling Effects in Alcohol/Water Pervaporation across Polymeric Membranes
title_short Highlighting Thermodynamic Coupling Effects in Alcohol/Water Pervaporation across Polymeric Membranes
title_sort highlighting thermodynamic coupling effects in alcohol/water pervaporation across polymeric membranes
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751729/
https://www.ncbi.nlm.nih.gov/pubmed/31552372
http://dx.doi.org/10.1021/acsomega.9b02255
work_keys_str_mv AT krishnarajamani highlightingthermodynamiccouplingeffectsinalcoholwaterpervaporationacrosspolymericmembranes