Porous Ceramic Membrane Supports Research Articles

Fabrication of alumina ceramic membrane supports using LCD 3D printing and titania nanoparticle doping

The integration of 3D printing technology into the production of ceramic membranes has garnered significant interest. Nonetheless, challenges persist in fabricating macroporous supports with both high porosity and strength through 3D printing. In this study, titania nanoparticles were introduced to facilitate the fusion of alumina nanoparticles. This freed the pores occupied by alumina nanoparticles and enhanced the connections between micron-sized alumina particles. Consequently, both the permeability and strength of the ceramic membrane supports were improved. The impact of ceramic slurry composition on photocuring performance, sintering processes, and the addition of titania nanoparticles on the microstructure and properties of the porous ceramic membrane support were investigated. The optimized membrane support featured a pore size of approximately 1.36 µm, achieving a porosity of 42.4% and a pure water permeance of 3700 L·m−2·h−1·bar−1. These findings provide a fundamental groundwork for subsequent endeavors in the development of high-performance ceramic membranes.

High-temperature self-healing behavior of reaction-bonded silicon carbide porous ceramic membrane supports

Reaction-bonded silicon carbide porous ceramics (SCPCs) are increasingly employed as membrane supports for the high-temperature filtration. However, the inevitable expansion of cracks limits their application. Herein, we studied the crack propagation behavior of SCPCs and discovered the commendable self-healing properties at high temperatures. Results show that the optimal healing conditions are 1200 °C for 2 h, which can recover the strength from 41.9% to 88.4%, and maintain the initial pore structure and permeance. This is mainly attributed to the infiltration of the multi-phase oxide melt that healed the cracks rather than the oxidation of SiC. Neck cracks are more prone to healing than surface cracks on SiC particles due to the residual compressive stress and a high proportion of melt volume. Nonetheless, the recovery of residual compressive stress and the crack width constrain the upper limit of strength recovery. These insights lay the groundwork for the high-temperature industrial application of SCPCs.

Overcoming the Trade-off between Water Permeation and Mechanical Strength of Ceramic Membrane Supports by Interfacial Engineering.

Porous ceramic membrane supports with high mechanical strength and permeation are required for highly permeable ceramic membranes. The water permeation of a ceramic membrane support is largely dependent on its level of open porosity, which can be however generally detrimental to the mechanical strength. In this work, low-cost kaolin nanoflakes were rationally composited with coarse alumina particles, and multichannel flat-sheet ceramic supports were successfully fabricated by extrusion and subsequent partial sintering. The macroscopic properties, microstructure characteristics, permeability, and mechanical strength of the ceramic membrane supports were systematically established and comprehensively studied. The incorporation of kaolin nanoflakes effectively reduced the sintering temperature to about 1200 °C. An interesting evolution of the pore structure was evidenced with the increase in sintering temperature. Interestingly, the porous ceramic supports prepared at 1400 °C with a nominal pore size of 1.47 μm showed the highest water permeability of 9911.9 ± 357.5 LMHB, and at the same time the flexural strength reached 109.6 ± 4.6 MPa. The much improved permeability was attributed to the unique multilevel pore structures, and the enhanced flexural strength mainly originated from the strongly interfacial bonding, as evidenced by the trans-granular fracture behavior. Also, the ceramic membrane supports exhibited excellent chemical resistance and good removal efficiency for oily wastewater. This work highlights the significant role of interfacial engineering in simultaneously improving the water permeation and mechanical strength, thereby overcoming their trade-off in porous ceramic membrane supports.

Effects of the Sintering Temperature on the Properties of Porous Ceramic Membrane Support Made of Fly Ash, Kaolin, and Claystone

In this article, the influence of the sintering temperature on the properties of porous ceramic membrane support made of low-cost inorganic materials is reported. Fly ash was used as a dominant component since it presents cheap, abundant waste material and can be activated by alkalis to form porous structure with great mechanical resistance. Fly ash from coal combustion and additives, which consist of natural kaolin and claystone, were mixed with 5M NaOH solution to make a paste suitable for extrusion. Properties of created tubular porous supports, sintered at temperature ranging from 900 to 1100 °C, were characterized using a number of methods. Tubes sintered at 1000 °C were selected for microfiltration purpose. The morphology of the surface of these samples, studied by scanning emission microscopy (SEM) show homogeneous and crack free structure. Mercury porosimetry indicates uniform pore size distribution with average pore size value of 2.5 μm and pore volume of 38 % and show good mechanical resistance (7.7 MPa). These properties make fly ash-based ceramics suitable as membranes supports for microfiltration membranes technology. Keywords: Ceramics; Fly ash; Membrane support; Sintering. DOI 10.35180/gse-2020-0044

Study on the Preparation and Properties of Talcum-Fly Ash Based Ceramic Membrane Supports.

Ceramic membrane method for moisture recovery from flue gas of thermal power plants is of considerable interest due to its excellent selection performance and corrosion resistance. However, manufacturing costs of commercial ceramic membranes are still relatively expensive, which promotes the development of new methods for preparing low-cost ceramic membranes. In this study, a method for the preparation of porous ceramic membrane supports is proposed. Low-cost fly ash from power plants is the main material of the membrane supports, and talcum is the additive. The fabrication process of the ceramic membrane supports is described in detail. The properties of the supports were fully characterized, including surface morphology, phase composition, pore diameter distribution, and porosity. The mechanical strength of the supports was measured. The obtained ceramic membrane supports displays a pore size of about 5 μm and porosity of 37.8%. Furthermore, the water recovery performance of the supports under different operating conditions was experimentally studied. The experimental results show that the recovered water flux varies with operating conditions. In the study, the maximum recovered water flux reaches 5.22 kg/(m2·h). The findings provide a guidance for the ceramic membrane supports application of water recovery from flue gas.

Effect of Type and Content of Pore-forming Agents on Properties of Porous Alumina Membrane Support

Porous ceramic membrane support with high porosity and high mechanical strength has been fabricated by adding the pore-forming agents, and using three particle sizes of alumina (coarse, medium and fine) as raw material. The effects of the type and the content of the pore-forming agents on the porosity, pore diameter and flexural strength of the membrane supports are studied in detailed. The results show that both the type and the content of the pore-forming agent can be effectively optimized to improve the mechanical and microstructural properties of the alumina support. Added 5 wt% of starch as the pore-forming agent, the porous ceramic membrane support calcinated at 1650°C for 2 h has the porosity of >33%, the flexural strength of > 45 MPa, the pore size of about 6∼8 μm. The amount of pore-forming agent plays a decisive role on the porosity and pore size of porous ceramic membrane support based on SEM characterization.

Improvement of microcracks resistance of porous aluminium titanate ceramic membrane support using attapulgite clay as additive

Attapulgite (ATP) clay as an important ceramic raw material appears with natural nano-rod like morphology and widely co-exists with other minor minerals. To improve the mechanical performance and to reduce the sintering temperature of aluminium titanate (AT) ceramic membrane support, porous aluminium titanate ceramic has been prepared from Al2O3-TiO2 system mixed with attapulgite clay by solid-phase reaction at relative low temperature 1300°C. The added contents of attapulgite clay were 0%, 10%, 15%, 20%, 25% and 30% in weight percent ratio, respectively. The phase composition, open porosity, strength, sintering behavior and microstructure as well as pore size distribution of porous aluminium titanate ceramic were systematically investigated. The XRD analysis suggests that the enhanced secondary phase mullite was produced when sintering temperature was above 1200°C with added attapulgite clays. The SEM images show that microcracks caused by the grain anisotropy of generated aluminium titanate were increased with the rising of sintering temperature. Both the maximum pore size and average pore size decrease with the increasing sintering temperature as the specimen was reacted with some attapulgite clay. Under the condition of 25wt% attapulgite clay addition and sintering temperature of 1300°C, the obtained porous ceramic membrane support of aluminium titanate has a open porosity of 32.41% and bending strength of 45.48MPa.

Preparation and Development of Porous Ceramic Membrane Supports Fabricated by Extrusion Technique

Ceramic membranes have been widely used in petroleum-chemical industry, food industry and pharmaceutical industry due to several characteristics such as high thermal and chemical stability, high filter precision, chemical resistance, and mechanical strength. Porous ceramic membrane supports are the essential part of ceramic membranes. A survey of the main preparation techniques of porous ceramic membrane supports and their characteristics was introduced in this paper. Emphasis was placed on the mechanism of the response of the support structure and performance to various technical parameters in the extrusion forming process, such as extrusion process, raw materials, additives, and sintering. In addition, the present technical issues to address and the development trends of porous ceramic membrane supports were also proposed herein.

Preparation and characterization of low cost porous ceramic membrane support from kaolin using phase inversion/sintering technique for gas separation: Effect of kaolin content and non-solvent coagulant bath

The aim of this study is to investigate the feasibility of using kaolin as a starting material in ceramic membrane support preparation using phase inversion/sintering technique at different kaolin content and non-solvent coagulant bath. The ceramic suspension was prepared by mixing the kaolin, polyethersulfone (PESf) as binder, N-methyl-2-pyrrolidone (NMP) as solvent and Arlacel as dispersant using a magnetic stirrer; drying and sintering process at temperature of 1200°C. By varying the kaolin contents, different morphologies of ceramic support were obtained due to the variations in viscosity of ceramic suspensions. Similarly, different non-solvent coagulant bath was found to affect the membrane support structure through liquid–liquid demixing process and at the same time affected membrane support's roughness, porosity, pore size distribution and strength. All ceramic supports possessed high gas permeation with no separation capability, proven the suitability as ceramic membrane support. The cost for the prepared ceramic membrane support in this work is as low as $5.97, prepared at 54.0g kaolin content and immersed into distilled water.

Feasible recycling of industrial waste coal fly ash for preparation of anorthite-cordierite based porous ceramic membrane supports with addition of dolomite

Recycling of industrial solid state waste is always the priority solution in the prospect of waste management. This work demonstrated a new method converting coal fly ash (CFA) industrial waste to anorthite-cordierite-based porous ceramic membrane supports (ACCMS), through high-temperature sintering with additions of dolomite mineral. Characterization of as-prepared ACCMS included phase composition, microstructure, pore structure, N2 and water permeability, and mechanical properties. From dilatometric measurements, the densification temperature of a sample with 28.43wt.% dolomite addition was extended to 1100°C compared to 1060°C for that of a sample without any dolomite. For samples sintered at 1150°C, their open porosity increased from 25.2±0.5% to 46.5±0.2% when dolomite addition increased from 0 to 28.43wt.%. It is suggested that this level of dolomite addition significantly inhibited the sintering behavior of CFA.

Synthesis of novel titania membrane support via combustion synthesis route and its application in decolorization of aqueous effluent using microfiltration

A simple preparation method for synthesizing porous ceramic membrane support was developed from nanocrystalline titania powder using solution combustion synthesis. Different characteristics of combustion-synthesized titania membranes such as surface morphology, porosity, pore size, pure water and solvent permeability were measured using advanced characterization techniques. Novel titania membrane support sintered at 450 °C showed mean pore diameter 0.33 µm, porosity of about 77.5 %, and pure water permeability 20.31 × 10−5 L h−1 m−2 Pa−1. Combustion-synthesized titania membrane supports were used in decolorization of commercial dye-based ink effluent using microfiltration. Effects of different parameters such as pressure, initial concentration of ink effluent, and pH on decolorization of ink effluent were studied. Furthermore, combustion-synthesized titania membranes operated at lower pressure (1 × 105 Pa) showed significant color removal (>99 %) and moderate chemical oxygen demand reduction with lower membrane fouling during decolorization of water-based ink effluent.

Effects of B4C on the microstructure and phase transformation of porous SiC ceramics

Porous SiC ceramics sintered with B4C additive exhibit excellent corrosion resistance in hot acidic and basic solutions compared with traditional porous ceramic membrane supports. The effects of B4C on the density, phase composition, and microstructure of porous 6H–SiC ceramics were investigated in this study. The phase composition and microstructure of the as-prepared samples were characterized through X-ray diffraction, Raman spectrum, scanning electron microscopy, and electron probe microanalyzer equipped with wavelength dispersive spectrometry. B4C promoted the sintering of porous SiC ceramics within the temperature range of 2100–2200°C. The B4C content higher than 0.5wt% induced the phase transformation of 6H–SiC to 4H–SiC at 2200°C, resulting in the formation of large plate-like 4H–SiC grains, which significantly improved the flexural strength of the porous ceramics. The mechanisms of phase transformation and grain formation were also elucidated.

Coal fly ash industrial waste recycling for fabrication of mullite-whisker-structured porous ceramic membrane supports

SEM images of mullite membrane support (a) without addition, (b) with addition of AlF3, (c) with addition of MoO3and (d) with addition of AlF3and MoO3.

Waste-to-resource preparation of a porous ceramic membrane support featuring elongated mullite whiskers with enhanced porosity and permeance

Different from traditional particle packing structure, a porous structure of ceramic membrane support was fabricated, featuring elongated mullitewhiskers with enhanced porosity, permeance and sufficient mechanical strength. The effect of additives (MoO3and AlF3) and sintering procedureon open porosity, mechanical properties, pore size distribution, micro-structure, phase structure, and permeance of the membrane supports wascharacterized in detail. The introduction of MoO3and AlF3promoted formation of a porous whisker-interlocked structure, which effectivelyimproved open porosity and permeance. A mullite membrane support containing 5 wt.% MoO3and 4 wt.% AlF3exhibited an open porosity ashigh as 48.6 ± 0.5%, a mechanical strength of 81.2 ± 3.2 MPa at 1200◦C, and the value of permeance was higher than the membrane without anyadditives. Such enhancements in porosity and permeance, with sufficient mechanical strength, were a result of tortuosity decrease due to a porousstructure of interlocked mullite whiskers.© 2014 Elsevier Ltd. All rights reserved.

Effect of TiO 2 addition on the fabrication of ceramic membrane supports: A study on the separation of oil droplets and bovine serum albumin (BSA) from its solution

Low cost porous ceramic membrane support was prepared using kaolin, pyrophyllite, feldspar, ball clay, quartz and calcium carbonate mixture along with PVA as a binder. The main intention of this work is to study the changes in the properties of the membrane supports (pore size, porosity, mechanical strength and pure water permeability) by the addition of titanium dioxide (TiO 2). Three membrane supports, namely, support-I, 3G and 6G supports (naming is based on the loading of TiO 2) were prepared by uniaxial compaction method. All the membrane supports were sintered at 950 °C and systematically analyzed using thermogravimetric (TG), particle size distribution (PSD), X-ray diffraction (XRD), N 2 adsorption–desorption and scanning electron micrograph (SEM) analysis. The porosity of the support-I, 3G and 6G supports was found to be 44, 38 and 36% with an average pore diameter of 0.98, 0.93 and 0.83 μm, respectively. The flexural strength of the membrane supports was increased with the addition of TiO 2 and ranges between 28 and 33 MPa. Solvent permeation studies through these membrane supports revealed that the non polar solvents were more permeable than the polar solvents and the transport mechanism was mainly controlled by viscosity of the solvents. Performance of the membrane supports was investigated for oil-in-water emulsion separation by varying the feed concentration and applied pressure. A maximum rejection of 99% was obtained with 6G support for an oil concentration of 200 ppm. Also, an attempt has been made for the separation of bovine serum albumin (BSA) from its solution using these membrane supports and a reasonable rejection of 40% was obtained for 100 ppm of BSA solution. Research highlights ► Effect of addition of TiO 2 on the properties of the porous ceramic membrane supports was investigated. ► Potential of the supports was tested for oil and BSA separation from its solution. ► Higher rejection for oil (99%) and moderate rejection for BSA (40%) were obtained. ► Pore fouling mechanisms were also investigated for the oil-in-water emulsion system.

Synthesis and characterization of nanocomposite MCM-41 (‘LUS’) ceramic membranes

A new type of nanocomposite membranes, MCM-41 (‘LUS’)-based material networks grown into porous ceramic membrane support walls (alumina and zirconia), were prepared. Physical characterization (low-angle XRD, TPD, SEM–EDX) confirm the sole presence of the LUS mesostructure (BJH pore size ≈3.2nm), and in a high enough amount to plug the pores of the tubular supports. Single gas hydrodynamic characterization shows that the contribution of defects (i.e. viscous flux) is negligible or comparable to reference mesoporous commercial membranes (5nm pore size γ-alumina), but with a considerably enhanced permeance for gases and water, as well as, a single pore size. When compared to literature results on similar organized mesoporous membranes, this work shows even greater improvements.

Theory of batchwise centrifugal casting

AbstractIn batchwise centrifugal casting a cylindrical mold is filled with suspension and rotated rapidly around its axis. This results in the movement of the particulate phase toward the cylinder wall and the formation of a tubular cast. Theory is presented for particle transport in the suspension phase and subsequent cast growth using concepts from the related fields of centrifugal sedimentation and centrifugal separation. Most attention is given to the situation of complete mold filling, which allows for several distinct simplifications. Analytical expressions for suspension concentration and cast growth are presented for the case of unhindered settling. Numerical simulations are made for hindered settling. The outcome shows a good agreement with experiments in which homogeneous porous ceramic membrane supports are made from a submicronsized α‐alumina powder.