GR Semicolon EN

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dc.contributor.author
Piperidou, Eirini
en
dc.date.accessioned
2021-09-29T09:29:51Z
dc.date.available
2021-09-29T09:29:51Z
dc.date.issued
2021-09-29
dc.identifier.uri
https://repository.ihu.edu.gr//xmlui/handle/11544/29901
dc.rights
Default License
dc.subject
CVD
en
dc.subject
Hydrophobic ceramic membranes
en
dc.subject
Immersion
en
dc.title
Experimental investigation of CO2 capture concepts for maritime applications
en
heal.type
masterThesis
en_US
heal.creatorID.email
eirinipiper95@gmail.com
heal.generalDescription
The thesis is experimental in nature, investigating two different methods, immersion and chemical vapor deposition (CVD), for increasing the hydrophobicity on three different ceramic membranes, for application in CO2 capture.
en
heal.dateAvailable
2021-06-29
heal.language
en
en_US
heal.access
free
en_US
heal.license
http://creativecommons.org/licenses/by-nc/4.0
en_US
heal.recordProvider
School of Science and Technology, MSC in Energy and Finance
en_US
heal.publicationDate
2021-06-29
heal.abstract
Ceramic membranes are chemically, thermally and mechanically stable materials with well controlled pore size distribution which could be promising potential candidates for numerous applications, ranging from liquid filtration to membrane distillation, pervaporation and gas separation. Metal oxides such as alumina, titania, zirconia and silica are the main materials for ceramic membranes preparation. These materials have an intrinsic hydrophilic character due to the hydroxyl groups on their surface, leading to preferential and rapid water penetration in the membranes pore structure. This makes them unsuitable for some applications like membrane distillation or gas absorption in membrane contactors. For this reason, a number of different methods have been proposed to turn hydrophilic ceramic membranes to hydrophobic. This study focuses on the silane grafting method via two different techniques, i.e. immersion and chemical vapor deposition (CVD). In both techniques, grafting occurs through surface reactions between the hydroxyl groups found in the membrane and the Si–O–alkyl groups of the silane. The immersion technique is the most widely used due to its simplicity, while the CVD technique is a promising potential and in-principle more precise and controllable alternative which has not been widely assessed. The proposed hydrophobic modification methods were applied on different types of tubular ceramic membranes, i.e. Al2O3 (mean pore size ~70nm), ZrO2 (mean pore size ~4nm) and TiO2 (mean pore size ~2nm). A thorough literature search for potential candidate silane agents, suitable for hydrophobic treatment, was conducted. The hexyltrimethoxysilane (C9H22O3Si) was identified by our group as a potential cost-effective alternative (about an order of magnitude lower cost) to 1H,1H,2H,2H-perfluorodecyltriethoxysilane, which is considered the “gold standard” in the literature. The grafting procedure included an initial membrane pre-conditioning stage (same for both methods), where the ceramic membranes were thoroughly washed with distilled water and ethanol and then dried overnight at 110°C. Grafting solutions (0.1 M) for the immersion method were prepared by dissolving an appropriate amount of hexyltrimethoxysilane in chloroform (stabilized by 1% ethanol). The membranes were placed in a sealed volumetric cylinder, filled with the grafting solution for 6h and then dried overnight at 110°C. In the case of the CVD method, the membranes were placed in a sealed membrane cell and the hexyltrimethoxysilane (stabilized by 1% ethanol) was placed in a bubbler. Bubbler and membrane cell temperatures were set at 60 oC and N2 was used as carrier gas to transfer silane vapors to the membrane for 6h. Then the membrane was dried at 110°C under N2 for 6h. The efficacy of both methods was evaluated by water contact angle measurements and confirmed by monitoring the gas pressure needed for bubbles formation in the water, in a gas-liquid membrane contactor setup. Before membrane modification, all water contact angle measurements were well below 90o and the water droplet rapidly penetrated in the membrane porous structure. Moreover, in the gas-liquid membrane contactor setup, water penetrated in the membrane pores and no gas bubbles could be observed for gas overpressures up to 6 bars (the upper limit of the used setup). With the exception of alumina membranes modified with the immersion method, both methods proved effective to produce hydrophobic membranes (water contact angle >90o and stable water droplet in the membrane surface). However, the CVD method seems to provide the best results. The hydrophobic character of modified membranes was also confirmed in the gas-liquid membrane contactor set-up where only a slight gas overpressure (~0.2 bar) was adequate to observe gas bubbles forming in the liquid phase.
en
heal.advisorName
Skevis, George
en
heal.committeeMemberName
Skevis, George
en
heal.committeeMemberName
Heracleous, Eleni
en
heal.committeeMemberName
Lappas
en
heal.academicPublisher
IHU
en
heal.academicPublisherID
ihu
en_US
heal.numberOfPages
54
en_US


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