Formation of micro-channels in ceramic membranes – Spatial structure, simulation, and potential use in water treatment

Lee, Melanie; Wang, Bo; Wu, Zhentao; Li, K.

doi:10.1016/j.memsci.2015.02.023

Cited by 62 publications

(27 citation statements)

References 55 publications

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“…There are many theories that different researchers have adopted for the source of these micro-channels, such as: the rapture of membrane surface [22], the growth of polymer-lean nuclei [23], viscosity gradient [24,25], surface tension gradient [25][26][27], or the gradient of solidification and shrinkage rate along the interface [28]. As discussed in a previous study, the formation of the micro-channels may also be attributed to the Rayleigh-Taylor Instability, which occurs when there is an acceleration on the interface between two fluids of different masses, and arises from perturbing waves at the interface [2]. Possible sources of acceleration that can cause interfacial instabilities include the solvent and non-solvent exchange and polymer precipitation, which leads to the accelerated movement of the interface towards the polymer solution/ceramic suspension side.…”

Section: Designmentioning

confidence: 87%

“…Therefore, NMP was chosen to solvate the PESf in both the outer polymeric and inner ceramic layers, according to previous literature [2]. The bore fluid was chosen to be a mixture of nonsolvent and solvent in order to reduce the precipitation rate at the lumen side, to prevent closure of the micro-channels in order to form an open lumen.…”

Section: Designmentioning

confidence: 99%

“…Firstly, they can produce asymmetric membranes in a single step requiring one heat treatment session only, and secondly, the method is versatile and can be used to form a wide range of different membrane configurations: flat discs, hollow fibres, multi-channel monoliths, etc [1][2][3][4]. The ability to form finger-like micro-channels in the membranes due to interfacial instabilities not only reduces mass transfer resistance, giving rise to competitive pure water permeation fluxes, but also widens the possible applications of these ceramic membranes [4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…Hence, if the pore size of the separation surface meets separation requirements, the other surface or sponge-like layers do not offer any improvements in selectivity, but instead creates additional resistances to mass transfer. By eliminating the redundant dense surface and sponge-like layer, the pure water flux of the membranes can be dramatically increased [2].…”

Section: Introductionmentioning

confidence: 99%

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New designs of ceramic hollow fibres toward broadened applications

Lee

Wang

2016

Journal of Membrane Science

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Three structural designs for ceramic membranes have been achieved for the first time through the co-extrusion of polymeric and ceramic layers. During co-extrusion, micro-channels are initiated due to the Rayleigh-Taylor instability and they propagate through the different layers.The polymeric layer(s) is then calcined off during the heat treatment step, which opens the microchannels and following sintering a ceramic membrane with open micro-channels ranging from a few to a few tens of micrometres in diameter can be formed. These long, straight and nontortuous micro-channels can be controlled to be open at any or all of the surfaces. Design 1 has open micro-channels passing through the entire membrane wall, Design 2 has a separation layer at the lumen and open micro-channels at the shell side, and Design 3 has open micro-channels from both lumen and shell sides sandwiching a separation layer of sponge-like structure. Aside from having much improved mass transfer property due to the reduced effective membrane thickness, they can be easily incorporated into hybrid systems with anticipated improvements in unit compactness and performance. The pure water permeation of Design 2 reached up to 159, 000 L/m 2 h bar with pore sizes in the micro-filtration range. The micro-channels are easily accessible from the shell/lumen side; therefore catalysts or adsorbents can be easily deposited into the micro-channels. Examples of possible applications include a high-efficiency dispersing device realised with Design 1; a gas chromatography column for gas separation with very low pressure drop realised with Design 2 and a highly compact membrane micro-reactor for consecutive reactions proposed with Design 3.

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Section: Designmentioning

confidence: 87%

Section: Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New designs of ceramic hollow fibres toward broadened applications

Lee

Wang

2016

Journal of Membrane Science

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“…However, a major problem presented by the membranes is the decrease in permeability over its use due to fouling caused by organic matter contained in the raw water and microorganisms that adhere to the microporous wall or inside the pores 3,4 . Many studies described in literature proved that the use of ceramic membranes offer several advantages over the polymer ones, especially with respect to durability, resistance to high temperatures and pressures, easy clean condition, biological stability and chemical inertness 5,6 . The main drawback presented by ceramic membranes is their high cost, due to the used raw materials that are imported and synthetic 7,8 .…”

Section: Introductionmentioning

confidence: 99%

Characterization of Mullite Ceramic Membranes and their Application in the Removal Escherichia Coli

et al. 2016

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Fabrication of Graphene‐Covered Micro‐Tubes for Process Intensification

et al. 2019

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Graphene is known for its high surface-area-to-mass ratio. However, for using graphene in engineering processes such as catalytic reactors or heat exchangers, a high surface-area-to-volume ratio is essential. Currently, graphene is only prepared in sheet form, which limits its surface-area-to-volume ratio to around 200 m 2 m À3 . Herein, a technique based on chemical vapor deposition (CVD) to realize graphene on a micro-tubular substrate to not only substantially increase its surface-area-to-volume ratio to a value over 2000 m 2 m À3 but also to eliminate the maldistribution of flows commonly unavoidable in flat-sheet configurations is proposed and demonstrated. This approach uses a dual-layer micro-tubular substrate fabricated by a phase-inversion technique. In the substrate, a thin copper outer layer is used to enable the CVD growth of graphene, and an inner Cu-Fe layer is adopted to provide a strong mechanical support. This approach is feasible to produce graphene with a very high surface-area-to-volume ratio for possible applications in catalytic reactors or heat exchangers, although problems such as inter-diffusion between the two metal layers and defects in graphene need to be addressed. To the best of our knowledge, this study is the first attempt to prepare graphene with high surface-area-to-volume ratios by a CVD route.

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Formation of micro-channels in ceramic membranes – Spatial structure, simulation, and potential use in water treatment

Cited by 62 publications

References 55 publications

New designs of ceramic hollow fibres toward broadened applications

New designs of ceramic hollow fibres toward broadened applications

Characterization of Mullite Ceramic Membranes and their Application in the Removal Escherichia Coli

Fabrication of Graphene‐Covered Micro‐Tubes for Process Intensification

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