Fabrication and Applications of Nanoporous Alumina Membranes

Kah Peng Lee

Research output: ThesisDoctoral Thesis

Abstract

The performance of membranes in various processes is largely dependent on
their morphological properties. Thus, membrane structure has been continuously
optimised for different applications. Anodic alumina membranes (AAMs) exhibit
self-ordered pore structure and the pore size can be tuned in the sub-micrometre
range. The aim of this PhD project is to propose and develop AAMs for the
applications of membrane filtration and emulsification with potential for scale-up.
In the project, the AAMs were initially fabricated in flat sheet form to optimise the
process parameters to obtain membranes with a high quality of pore structure.
The membrane pore diameter can be readily controlled by the anodization
voltage. While AAMs are normally symmetric, by manipulating the anodization
voltage, asymmetric AAMs consists of stem pores and active pores have been
successfully made. After that, the flat AAMs with symmetric and homogeneous
structure were used as a platform to study for surface modification and fluid
transport in nano-channels. The surface chemistry and wettability of the
membranes has been altered by grafting of silane molecules and carbon coating
by chemical vapour deposition. Fluid flow measurement through pristine AAMs
with pore diameter in the 20 nm to 100 nm range shows flow enhancement effect,
experimentally for the first time, can occur in hydrophilic materials.
Subsequently, tubular AAMs were fabricated using aluminium alloy tubes, to be
assessed for ultrafiltration and membrane emulsification processes. The pore
structure of the tubular AAMs was analogous to flat membranes. Despite the
reduced pore circularity and hexagonal arrangement originated from the
presence of impurities in the starting materials, the narrow pore size distribution
was not compromised. In a selectivity-permeability analysis, the asymmetric
tubular AAMs outperformed most of the commercial ceramic membranes but
their flux was very low when compared to polymeric membranes. A bovine serum
albumin filtration test showed that complete pore blocking-cake filtration model
can be used to describe the fouling behaviour. Finally, symmetric tubular
membranes were used to study dead-end and cross-flow emulsification
processes. The resulting emulsions show low polydispersity. Using a membrane
with 25 nm average pore diameter, the obtained average droplet size was as low
as 120 nm during a cross-flow emulsification. This is by far the smallest achieved
average droplet size by cross-flow membrane emulsification.
LanguageEnglish
QualificationPh.D.
Awarding Institution
  • University of Bath
Supervisors/Advisors
  • Mattia, Davide, Supervisor
  • Arnot, Thomas, Supervisor
Award date31 Aug 2013
StatusPublished - Aug 2013

Fingerprint

Aluminum Oxide
Membranes
Fabrication
Emulsification
Pore structure
Pore size
Silanes
Polymeric membranes
Ceramic membranes
Membrane structures

Keywords

  • membranes
  • flow enhancement
  • Ultrafiltration
  • emulsification
  • ceramic

Cite this

Fabrication and Applications of Nanoporous Alumina Membranes. / Lee, Kah Peng.

2013.

Research output: ThesisDoctoral Thesis

Lee, KP 2013, 'Fabrication and Applications of Nanoporous Alumina Membranes', Ph.D., University of Bath.
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title = "Fabrication and Applications of Nanoporous Alumina Membranes",
abstract = "The performance of membranes in various processes is largely dependent ontheir morphological properties. Thus, membrane structure has been continuouslyoptimised for different applications. Anodic alumina membranes (AAMs) exhibitself-ordered pore structure and the pore size can be tuned in the sub-micrometrerange. The aim of this PhD project is to propose and develop AAMs for theapplications of membrane filtration and emulsification with potential for scale-up.In the project, the AAMs were initially fabricated in flat sheet form to optimise theprocess parameters to obtain membranes with a high quality of pore structure.The membrane pore diameter can be readily controlled by the anodizationvoltage. While AAMs are normally symmetric, by manipulating the anodizationvoltage, asymmetric AAMs consists of stem pores and active pores have beensuccessfully made. After that, the flat AAMs with symmetric and homogeneousstructure were used as a platform to study for surface modification and fluidtransport in nano-channels. The surface chemistry and wettability of themembranes has been altered by grafting of silane molecules and carbon coatingby chemical vapour deposition. Fluid flow measurement through pristine AAMswith pore diameter in the 20 nm to 100 nm range shows flow enhancement effect,experimentally for the first time, can occur in hydrophilic materials.Subsequently, tubular AAMs were fabricated using aluminium alloy tubes, to beassessed for ultrafiltration and membrane emulsification processes. The porestructure of the tubular AAMs was analogous to flat membranes. Despite thereduced pore circularity and hexagonal arrangement originated from thepresence of impurities in the starting materials, the narrow pore size distributionwas not compromised. In a selectivity-permeability analysis, the asymmetrictubular AAMs outperformed most of the commercial ceramic membranes buttheir flux was very low when compared to polymeric membranes. A bovine serumalbumin filtration test showed that complete pore blocking-cake filtration modelcan be used to describe the fouling behaviour. Finally, symmetric tubularmembranes were used to study dead-end and cross-flow emulsificationprocesses. The resulting emulsions show low polydispersity. Using a membranewith 25 nm average pore diameter, the obtained average droplet size was as lowas 120 nm during a cross-flow emulsification. This is by far the smallest achievedaverage droplet size by cross-flow membrane emulsification.",
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month = "8",
language = "English",
school = "University of Bath",

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T1 - Fabrication and Applications of Nanoporous Alumina Membranes

AU - Lee,Kah Peng

PY - 2013/8

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N2 - The performance of membranes in various processes is largely dependent ontheir morphological properties. Thus, membrane structure has been continuouslyoptimised for different applications. Anodic alumina membranes (AAMs) exhibitself-ordered pore structure and the pore size can be tuned in the sub-micrometrerange. The aim of this PhD project is to propose and develop AAMs for theapplications of membrane filtration and emulsification with potential for scale-up.In the project, the AAMs were initially fabricated in flat sheet form to optimise theprocess parameters to obtain membranes with a high quality of pore structure.The membrane pore diameter can be readily controlled by the anodizationvoltage. While AAMs are normally symmetric, by manipulating the anodizationvoltage, asymmetric AAMs consists of stem pores and active pores have beensuccessfully made. After that, the flat AAMs with symmetric and homogeneousstructure were used as a platform to study for surface modification and fluidtransport in nano-channels. The surface chemistry and wettability of themembranes has been altered by grafting of silane molecules and carbon coatingby chemical vapour deposition. Fluid flow measurement through pristine AAMswith pore diameter in the 20 nm to 100 nm range shows flow enhancement effect,experimentally for the first time, can occur in hydrophilic materials.Subsequently, tubular AAMs were fabricated using aluminium alloy tubes, to beassessed for ultrafiltration and membrane emulsification processes. The porestructure of the tubular AAMs was analogous to flat membranes. Despite thereduced pore circularity and hexagonal arrangement originated from thepresence of impurities in the starting materials, the narrow pore size distributionwas not compromised. In a selectivity-permeability analysis, the asymmetrictubular AAMs outperformed most of the commercial ceramic membranes buttheir flux was very low when compared to polymeric membranes. A bovine serumalbumin filtration test showed that complete pore blocking-cake filtration modelcan be used to describe the fouling behaviour. Finally, symmetric tubularmembranes were used to study dead-end and cross-flow emulsificationprocesses. The resulting emulsions show low polydispersity. Using a membranewith 25 nm average pore diameter, the obtained average droplet size was as lowas 120 nm during a cross-flow emulsification. This is by far the smallest achievedaverage droplet size by cross-flow membrane emulsification.

AB - The performance of membranes in various processes is largely dependent ontheir morphological properties. Thus, membrane structure has been continuouslyoptimised for different applications. Anodic alumina membranes (AAMs) exhibitself-ordered pore structure and the pore size can be tuned in the sub-micrometrerange. The aim of this PhD project is to propose and develop AAMs for theapplications of membrane filtration and emulsification with potential for scale-up.In the project, the AAMs were initially fabricated in flat sheet form to optimise theprocess parameters to obtain membranes with a high quality of pore structure.The membrane pore diameter can be readily controlled by the anodizationvoltage. While AAMs are normally symmetric, by manipulating the anodizationvoltage, asymmetric AAMs consists of stem pores and active pores have beensuccessfully made. After that, the flat AAMs with symmetric and homogeneousstructure were used as a platform to study for surface modification and fluidtransport in nano-channels. The surface chemistry and wettability of themembranes has been altered by grafting of silane molecules and carbon coatingby chemical vapour deposition. Fluid flow measurement through pristine AAMswith pore diameter in the 20 nm to 100 nm range shows flow enhancement effect,experimentally for the first time, can occur in hydrophilic materials.Subsequently, tubular AAMs were fabricated using aluminium alloy tubes, to beassessed for ultrafiltration and membrane emulsification processes. The porestructure of the tubular AAMs was analogous to flat membranes. Despite thereduced pore circularity and hexagonal arrangement originated from thepresence of impurities in the starting materials, the narrow pore size distributionwas not compromised. In a selectivity-permeability analysis, the asymmetrictubular AAMs outperformed most of the commercial ceramic membranes buttheir flux was very low when compared to polymeric membranes. A bovine serumalbumin filtration test showed that complete pore blocking-cake filtration modelcan be used to describe the fouling behaviour. Finally, symmetric tubularmembranes were used to study dead-end and cross-flow emulsificationprocesses. The resulting emulsions show low polydispersity. Using a membranewith 25 nm average pore diameter, the obtained average droplet size was as lowas 120 nm during a cross-flow emulsification. This is by far the smallest achievedaverage droplet size by cross-flow membrane emulsification.

KW - membranes

KW - flow enhancement

KW - Ultrafiltration

KW - emulsification

KW - ceramic

M3 - Doctoral Thesis

ER -