Development of highly porous flat sheet polyvinylidene fluoride (PVDF) membranes for membrane distillation

Handle URI:
http://hdl.handle.net/10754/623474
Title:
Development of highly porous flat sheet polyvinylidene fluoride (PVDF) membranes for membrane distillation
Authors:
Alsaery, Salim A. ( 0000-0001-5035-6142 )
Abstract:
With the increase of population every year, fresh water scarcity has rapidly increased and it is reaching a risky level, particularly in Africa and the Middle East. Desalination of seawater is an essential process for fresh water generation. One of the methods for desalination is membrane distillation (MD). MD process separates an aqueous liquid feed across a porous hydrophobic membrane to produce pure water via evaporation. Polyvinlidene fluoride (PVDF) membranes reinforced with a polyester fabric were fabricated as potential candidates for MD. Non-solvent induced phase separation coupled with steam treatment was used to prepare the PVDF membranes. A portion of the prepared membrane was coated with Teflon (AF2400) to increase its hydrophobicity. In the first study, the fabricated membranes were characterized using scanning electron microscopy and other techniques, and they were evaluated using direct contact MD (DCMD). The fabricated membranes showed a porous sponge-like structure with some macrovoids. The macrovoid formation and the spongy structure in the membrane cross-sections contributed significantly to a high permeate flux as they provide a large space for vapor water transport. The modified PVDF membranes with steaming and coating exhibited a permeate flux of around 40 L/h m2 (i.e. 27-30% increase to the control PVDF membrane) at temperatures of 60 °C (feed) and 20 °C (permeate). This increase in the permeate flux for the modified membranes was mainly attributed to its larger pore size on the bottom surface. In the second study, the control PVDF membrane was tested in two different module designs (i.e. semi-circular pipe and rectangular duct module designs). The semi-circular module design (turbulent regime) exhibited a higher permeate flux, 3-fold higher than that of the rectangular duct module design (laminar regime) at feed temperature of 60 °C. Furthermore, a heat energy balance was performed for each module design to determine the temperature polarization coefficients (TPC). The turbulent module design showed higher TPC (0.5-0.58) than the laminar module (0.1-0.14) (i.e. a poor module design). This indicates that the effect of temperature polarization on the laminar flow was significant, which is below the reported TPC range of 0.4-0.70.
Advisors:
Peinemann, Klaus-Viktor ( 0000-0003-0309-9598 )
Committee Member:
Nunes, Suzana Pereira ( 0000-0002-3669-138X ) ; Pinnau, Ingo ( 0000-0003-3040-9088 )
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Chemical and Biological Engineering
Issue Date:
May-2017
Type:
Thesis
Appears in Collections:
Theses

Full metadata record

DC FieldValue Language
dc.contributor.advisorPeinemann, Klaus-Viktoren
dc.contributor.authorAlsaery, Salim A.en
dc.date.accessioned2017-05-11T12:00:37Z-
dc.date.available2017-05-11T12:00:37Z-
dc.date.issued2017-05-
dc.identifier.urihttp://hdl.handle.net/10754/623474-
dc.description.abstractWith the increase of population every year, fresh water scarcity has rapidly increased and it is reaching a risky level, particularly in Africa and the Middle East. Desalination of seawater is an essential process for fresh water generation. One of the methods for desalination is membrane distillation (MD). MD process separates an aqueous liquid feed across a porous hydrophobic membrane to produce pure water via evaporation. Polyvinlidene fluoride (PVDF) membranes reinforced with a polyester fabric were fabricated as potential candidates for MD. Non-solvent induced phase separation coupled with steam treatment was used to prepare the PVDF membranes. A portion of the prepared membrane was coated with Teflon (AF2400) to increase its hydrophobicity. In the first study, the fabricated membranes were characterized using scanning electron microscopy and other techniques, and they were evaluated using direct contact MD (DCMD). The fabricated membranes showed a porous sponge-like structure with some macrovoids. The macrovoid formation and the spongy structure in the membrane cross-sections contributed significantly to a high permeate flux as they provide a large space for vapor water transport. The modified PVDF membranes with steaming and coating exhibited a permeate flux of around 40 L/h m2 (i.e. 27-30% increase to the control PVDF membrane) at temperatures of 60 °C (feed) and 20 °C (permeate). This increase in the permeate flux for the modified membranes was mainly attributed to its larger pore size on the bottom surface. In the second study, the control PVDF membrane was tested in two different module designs (i.e. semi-circular pipe and rectangular duct module designs). The semi-circular module design (turbulent regime) exhibited a higher permeate flux, 3-fold higher than that of the rectangular duct module design (laminar regime) at feed temperature of 60 °C. Furthermore, a heat energy balance was performed for each module design to determine the temperature polarization coefficients (TPC). The turbulent module design showed higher TPC (0.5-0.58) than the laminar module (0.1-0.14) (i.e. a poor module design). This indicates that the effect of temperature polarization on the laminar flow was significant, which is below the reported TPC range of 0.4-0.70.en
dc.language.isoenen
dc.subjectMembrane Distillationen
dc.subjectPVDFen
dc.subjectHigh Permeate Fluxen
dc.subjectPolyvinylidene fluorideen
dc.subjectDCMD fluxen
dc.titleDevelopment of highly porous flat sheet polyvinylidene fluoride (PVDF) membranes for membrane distillationen
dc.typeThesisen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberNunes, Suzana Pereiraen
dc.contributor.committeememberPinnau, Ingoen
thesis.degree.disciplineChemical and Biological Engineeringen
thesis.degree.nameMaster of Scienceen
dc.person.id144189en
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