Solution-diffusion with defects model for pressure-assisted forward osmosis

Handle URI:
http://hdl.handle.net/10754/563815
Title:
Solution-diffusion with defects model for pressure-assisted forward osmosis
Authors:
Duan, Jintang ( 0000-0003-0878-0032 ) ; Litwiller, Eric ( 0000-0001-5366-0967 ) ; Pinnau, Ingo ( 0000-0003-3040-9088 )
Abstract:
An osmosis transport model is presented that combines the standard internal and external concentration polarization equations in the forward osmosis (FO) field with the selective layer transport equations first proposed by Sherwood in 1967. The Sherwood model describes water flux as the sum of a solute-selective, diffusive component driven by the sum of osmotic pressure and hydraulic pressure differences, and a nonselective, convective component driven by hydraulic pressure difference only. This solution-diffusion with defects (SDWD) model and the solution-diffusion (SD) model were compared against data collected using polyamide thin-film-composite (PA-TFC) and integrally-skinned asymmetric cellulose triacetate (CTA) membranes, evaluated in various configurations. When tested with pure water on the porous support side and 1.5. M (π=72.7. bar) sodium chloride solution on the selective layer side, applying 1.25. bar of hydraulic pressure to the porous support side increased water flux by an order of magnitude for PA-TFC membranes, but had negligible effect on CTA membrane flux. These large flux variations can be explained by the SDWD model, but not the SD model. To confirm the existence of defects, a PA-TFC membrane was coated with a uniform, highly water-permeable, nonselective polymer. After coating to block convection through defects, the influence of hydraulic pressure on water flux through this membrane essentially disappeared. Water flux through these defects is low (<1% of total water flux for PA-TFC membranes) and of little consequence in practical FO or reverse osmosis (RO) applications. But in pressure-assisted forward osmosis (PAFO) or pressure-retarded osmosis (PRO), convective transport through defects affects the solute concentration difference across the membrane selective layer, increasing or decreasing water flux through defect-free regions. The presence of defects may explain why membrane power density in PRO is lower than that predicted based on FO and RO tests. © 2014 Elsevier B.V.
KAUST Department:
Advanced Membranes and Porous Materials Research Center; Physical Sciences and Engineering (PSE) Division; Chemical and Biological Engineering Program
Publisher:
Elsevier BV
Journal:
Journal of Membrane Science
Issue Date:
Nov-2014
DOI:
10.1016/j.memsci.2014.07.018
Type:
Article
ISSN:
03767388
Sponsors:
Research reported in this publication was supported by King Abdullah University of Science and Technology (KAUST). The authors acknowledge HTI for providing FO membranes for this research. The authors also acknowledge Dr. Federico Pacheco for valuable discussions and Dr. Ali Behzad from KAUST Advanced Nanofabrication Imaging and Characterization Core Lab for assistance.
Appears in Collections:
Articles; Advanced Membranes and Porous Materials Research Center; Physical Sciences and Engineering (PSE) Division; Chemical and Biological Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.authorDuan, Jintangen
dc.contributor.authorLitwiller, Ericen
dc.contributor.authorPinnau, Ingoen
dc.date.accessioned2015-08-03T12:11:07Zen
dc.date.available2015-08-03T12:11:07Zen
dc.date.issued2014-11en
dc.identifier.issn03767388en
dc.identifier.doi10.1016/j.memsci.2014.07.018en
dc.identifier.urihttp://hdl.handle.net/10754/563815en
dc.description.abstractAn osmosis transport model is presented that combines the standard internal and external concentration polarization equations in the forward osmosis (FO) field with the selective layer transport equations first proposed by Sherwood in 1967. The Sherwood model describes water flux as the sum of a solute-selective, diffusive component driven by the sum of osmotic pressure and hydraulic pressure differences, and a nonselective, convective component driven by hydraulic pressure difference only. This solution-diffusion with defects (SDWD) model and the solution-diffusion (SD) model were compared against data collected using polyamide thin-film-composite (PA-TFC) and integrally-skinned asymmetric cellulose triacetate (CTA) membranes, evaluated in various configurations. When tested with pure water on the porous support side and 1.5. M (π=72.7. bar) sodium chloride solution on the selective layer side, applying 1.25. bar of hydraulic pressure to the porous support side increased water flux by an order of magnitude for PA-TFC membranes, but had negligible effect on CTA membrane flux. These large flux variations can be explained by the SDWD model, but not the SD model. To confirm the existence of defects, a PA-TFC membrane was coated with a uniform, highly water-permeable, nonselective polymer. After coating to block convection through defects, the influence of hydraulic pressure on water flux through this membrane essentially disappeared. Water flux through these defects is low (<1% of total water flux for PA-TFC membranes) and of little consequence in practical FO or reverse osmosis (RO) applications. But in pressure-assisted forward osmosis (PAFO) or pressure-retarded osmosis (PRO), convective transport through defects affects the solute concentration difference across the membrane selective layer, increasing or decreasing water flux through defect-free regions. The presence of defects may explain why membrane power density in PRO is lower than that predicted based on FO and RO tests. © 2014 Elsevier B.V.en
dc.description.sponsorshipResearch reported in this publication was supported by King Abdullah University of Science and Technology (KAUST). The authors acknowledge HTI for providing FO membranes for this research. The authors also acknowledge Dr. Federico Pacheco for valuable discussions and Dr. Ali Behzad from KAUST Advanced Nanofabrication Imaging and Characterization Core Lab for assistance.en
dc.publisherElsevier BVen
dc.subjectConcentration polarizationen
dc.subjectDefectsen
dc.subjectForward osmosisen
dc.subjectPressureen
dc.subjectSolution-diffusion modelen
dc.titleSolution-diffusion with defects model for pressure-assisted forward osmosisen
dc.typeArticleen
dc.contributor.departmentAdvanced Membranes and Porous Materials Research Centeren
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentChemical and Biological Engineering Programen
dc.identifier.journalJournal of Membrane Scienceen
kaust.authorDuan, Jintangen
kaust.authorLitwiller, Ericen
kaust.authorPinnau, Ingoen
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