Permeation and Separation Characteristics of Supported Alumina and Titania Membranes
TL;DR: In this paper, the preparation, characterization, water permeability, and filtration characteristics of α-alumina and titania membranes on alumina and on clay supports are described.
Abstract: Preparation, characterization, water permeability, and filtration characteristics of alumina and titania membranes on alumina and on clay supports are described. Commercial α-alumina and Gangetic silt have been used for the preparation of support disks. The effects of temperature and time of sintering on porosity and pore size distribution of the supports have been studied. A higher firing temperature reduces the porosity but increases the average pore diameter. The sol–gel technique has been used to prepare supported membranes of alumina and titania. Stability of the sols prepared was noted, and some of the sols were found to remain stable for about a year. Coating and firing cycles had to be repeated in order to get good membranes. However, SEM pictures show that cracks developed in membranes if more than five coatings were applied. The membranes had good water permeabilities. The rejection performances of the membranes were studied using bovine serum albumin of 66,000 dalton molecular weight. The depen...
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TL;DR: In this article, the applicability of different membrane pore blocking models for the prediction of flux decline mechanisms during dead end microfiltration of stable oil-in-water (o/w) emulsions using relatively low-cost ceramic membranes was addressed.
Abstract: This work addresses the applicability of different membrane pore blocking models for the prediction of flux decline mechanisms during dead end microfiltration (MF) of stable oil-in-water (o/w) emulsions using relatively low-cost ceramic membranes. Circular disk type membranes (52.5 mm diameter and 4.5 mm thickness) were prepared by the paste method using locally available low-cost inorganic precursors such as kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, and sodium metasilicate. Characterization of the prepared membrane was done by SEM analysis, porosity determination, and pure water permeation through the membrane. Hydraulic pore diameter, hydraulic permeability, and hydraulic resistance of the membrane was evaluated as 0.7 µm, 1.94 × 10−6 m3/m2·s·kPa and 5.78 × 1011 m2/m3, respectively. The prepared membrane was used for the treatment of synthetic stable o/w emulsions of 40 and 50 mg/L crude oil concentration in batch mode with varying trans-membrane pressure differentials ra...
66 citations
Cites background from "Permeation and Separation Character..."
...The higher cost of ceramic membranes is due to the utilization of expensive inorganic precursors such as alumina and zirconia and higher sintering temperature (more than 1100 C) during membrane fabrication (5,6)....
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TL;DR: In this paper, a tangential filtration process was implemented using porous ceramic tubes made of α-alumina produced by the slip-casting technique, which revealed a mean pore size of 0.5μm.
Abstract: A tangential filtration process was implemented in this study using porous ceramic tubes made of α-alumina produced by the slip-casting technique. These tubes were sintered at 1450 °C and characterized by mercury intrusion porosimetry, which revealed a mean pore size of 0.5 μm. The tubes were chemically impregnated with a zirconium citrate solution, after which they were calcined and heat treated at temperatures of up to 600 and 900 °C to eliminate volatile organic compounds and transform the zirconium citrate into zirconium oxide impregnated in the alumina in the form of nanoparticle agglomerates. The microporous pipes were tested on a microfiltration hydraulic system to analyze their performance in the demulsification of sunflower oil and water mixtures. The fluid-dynamic parameters of Reynolds number and transmembrane pressure were varied in the process. The volume of permeate was analyzed by measuring the Total Organic Carbon concentration (TOC), which indicated 99% of oil phase retention. The emulsified mixture was characterized by optical microscopy, while the morphology and composition of the impregnated microporous tubes were analyzed by scanning electron microscopy (SEM). Quantification of the TOC values for the tube impregnated once at 600 °C showed the best demulsification performance, with the concentration on permeate smaller than 10 mg/L. The impregnated tube sintered once at 900 °C presented low carbon concentration (smaller than 20 mg/L), has the advantage of presenting the greatest trans-membrane flux in relation to the other microporous tube.
28 citations
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14 Oct 2001
TL;DR: In this article, the authors developed a membrane filtration equipment for plate type ceramic membranes based on the results achieved with different kinds of wastewaters, mainly made with pulp and board mill wastewater, but some experiments were also made with a bore well water and a stone cutting mine wastewater.
Abstract: Laitinen Niina Development of a ceramic membrane filtration equipment and its applicability for different wastewaters Lappeenranta 2002 126 pp. Acta Universitatis Lappeenrantaensis 130 Diss. Lappeenranta University of Technology ISBN 951-764-689-5, ISSN 1456-4491 In this thesis the membrane filtration equipment for plate type ceramic membranes was developed based on filtration results achieved with different kinds of wastewaters. The experiments were mainly made with pulp and board mill wastewaters, but some experiments were also made with a bore well water and a stone cutting mine wastewater. The ceramic membranes used were -alumina membranes with a pore size of 100 nm. Some of the membranes were coated with a alumina layer to reduce the membrane pore size to 10 nm, and some of them were modified with different metal oxides in order to change the surface properties of the membranes. The effects of operation parameters, such as cross-flow velocity, filtration pressure and backflushing on filtration performance were studied. The measured parameters were the permeate flux, the quality of the permeate, as well as the fouling tendency of the membrane. A dynamic membrane or a cake layer forming on top of the membrane was observed to decrease the flux and increase separation of certain substances, especially at low cross-flow velocities. When the crossflow velocities were increased the membrane properties became more important. Backflushing could also be used to decrease the thickness of the cake layer and thus it improved the permeate flux. However, backflushing can lead to a reduction of retentions in cases where the cake layer is improving them. The wastewater quality was important for the thickness of the dynamic membrane and the membrane pore size influenced the permeate flux. In general, the optimization of operation conditions is very important for the successful operation of a membrane filtration system. The filtration equipment with a reasonable range of operational conditions is necessary, especially when different kinds of wastewaters are treated. This should be taken into account already in the development stage of a filtration equipment.
19 citations
Additional excerpts
...[Das and Maiti, 1998; Burggraaf, 1996, p.282; Wang et al., 1999; Das and Dutta, 1999; Grönroos et al., 1995; Levänen et al., 1994b; Hsieh, 1996, p.43, 50]...
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TL;DR: In this article, a controlled chemical reaction between titanium tetrabutoxide and oxalic acid at room temperature in non-aqueous medium was utilized to obtain a mixed precursor with composition.
Abstract: Controlled chemical reaction between titanium tetrabutoxide and oxalic acid at room temperature in non-aqueous medium was utilized to obtain a mixed precursor with composition [(TiOC 2 O 4 ·2.5H 2 O) 0.8 +(Ti(OH) 4 ) 0.2 ]. Various physico-chemical techniques namely micro and chemical analyzes, XRD, DTA/TGA/DTG, SEM, Mercury porosimetry were employed to characterize mixed precursor as well as TiO 2 obtained by its pyrolysis. The pyrolysis was carried out under controlled conditions in air at ( T =400°C/2 h shown by thermal analysis) to obtain anatase (TiO 2 ) powder. This powder consisted of mainly two types of agglomerates having spherical shapes with sizes ≈0.1 and ≥0.3 μm. Further, green disks made from the powder were sintered at 1000°C/2 h in static air to obtain mechanically stable TiO 2 membranes with 60% porosity. SEM studies on the same revealed uniform microstructure with 200–500 nm grain size. The sintered material has thermodynamically stable rutile phase, confirmed by XRD. Mercury porosimetry measurement indicated that most of the pores have pore radius between 2 and 10 nm with a few pores of radius between 100 and 400 nm. These membranes have bubble point radii between 1.0 and 7.75 μm and average pore radii from 0.4 to 1.0 μm depending on the sintering and annealing conditions.
17 citations
TL;DR: In this paper, a new type of Kieselguhr-Mullite (K-M) ceramic membrane substrate was fabricated by line compounding technique, where skeleton pores of Kiegguhr particles as the passage and dense Mullite as the linking substance.
Abstract: The properties of ceramic membrane substrate mainly affect the selective layer membrane on several aspects, such as operating condition and permeability. In this paper, a new type of Kieselguhr–Mullite (K–M) ceramic membrane substrate was fabricated by line compounding technique, where skeleton pores of Kieselguhr particles as the passage and dense Mullite as the linking substance. The substrate was proved by TGA, SEM, XRD, IR, mercury porsimetry and permeability measurement to be an ideal one with a narrow pore-size distribution of average pore-size 2.01 μm, porosity of 0.42 by volume and high permeability. There exist silica phase and Mullite phase stimulatingly, which demonstrates that it is successful in incorporating Mullite component by the precursor of silica–alumina sol. The front compressive strength of substrate is above 4.5 MPa and side one above 1.1 MPa when the content of Mullite phase exceeded to 10% (wt.%), which complete accorded to industrial applications.
10 citations
References
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01 Jan 1991
TL;DR: The developing use of inorganic membranes: a historical perspective is given in this paper, where the authors present the characteristics of the inorganic membrane in liquid phase applications, operating considerations and some aspects of system design.
Abstract: The developing use of inorganic membranes: a historical perspective. Synthesis of inorganic membranes. General characteristics of inorganic membranes. Permeation and separation characteristics of inorganic membranes in liquid phase applications. Liquid filtration and separation with inorganic membranes: operating considerations and some aspects of system design. Gas separations with inorganic membranes. Inorganic membrane reactors to enhance the productivity of chemical processes. Inorganic membranes in food and biotechnology applications. Inorganic membranes for the filtration of water. Wastewater treatment and process industry filtration applications.
402 citations
TL;DR: In this paper, the formation of supported microporous membranes (by IUPAC definition rpore < 1 nm), prepared by modification of mesoporous γ-alumina membranes with polymeric sols, is described.
Abstract: The formation is described of supported microporous membranes (by IUPAC definition rpore < 1 nm), prepared by modification of mesoporous γ-alumina membranes with polymeric sols. The mesoporous γ-alumina membranes, with a top-layer thickness in the order of 7–10 μm, and with pore radii of 2–2.5 nm, have a very high surface finish (mean roughness 40 nm). The amorphous microporous top-layer thickness is in the order of 60–100 nm. Gas transport properties are effectively improved as is shown by activated permeation and molecular sieve-like separation factors in the order of 50–200 for H2/CH4. These microporous top-layers can be prepared from a relatively wide range of sol structures; from inorganic oligomers which are too small to result in significant scattering with SAXS, to polymeric structures with fractal dimensions in the range: 1
218 citations
TL;DR: In this paper, the authors show that strongly and weakly adsorbing gases and a high loadings of the strongly adaption molecule in the zeolite poze are suppressed by the sorption and the mobility of strongly adsorbs, resulting in pore blocking effects.
Abstract: Polycrystalline randomly oriented defect free zeolite layers on porous -Al2O3 supports are prepared with a thickness of less than 5 μm by in situ crystallisation of silicalite-1. The flux of alkanes is a function of the sorption and intracrystalline diffusion. In mixtures of strongly and weakly adsorbing gases and a high loadings of the strongly adsorbing molecule in the zeolite poze, the flux of the weakly adsorbing molecule is suppressed by the sorption and the mobility of the strongly adsorbing molecule resulting in pore-blocking effects. The separation of these mixtures is mainly based on the sorption and completely different from the permselectivity. At low loadings of the strongly adsorbing molecules the separation is based on the sorption and the diffusion and is the same as the permselectivity. Separation factors for the isomers of butane (n-butane/isobutane) and hexane (hexane/2,2-dimethylbutane) are respectively high (10) and very high (> 2000) at 200°C. These high separation factors are a strong evidence that the membrane shows selectivity by size-exclusion and that transport in pores larger than the zeolite MFI pores (possible defects, etc) can be neglected.
204 citations
TL;DR: In this article, a capillary pressure drop is created by bringing a microporous ceramic support into contact with a boehmite (γ-A1OOH) sol, which forces the dispersion medium of the sol to flow into the dry part of the support.
Abstract: Supported γ-A12O3 membranes are prepared by a dipping procedure. According to this method, a capillary pressure drop is created by bringing a microporous ceramic support into contact with a boehmite (γ-A1OOH) sol. This pressure drop forces the dispersion medium of the sol to flow into the dry part of the support. The sol particles are concentrated at the entrance of the pores and a gel is formed. This gel can be dried and calcined to form a crack-free alumina membrane with pores measuring only a few nanometers, if the membrane thickness after calcination is about 5 μm or less. The gel formation process can be quantitatively well described with the slibcasting model. The observations that the membrane thickness increases linearly with the square root of the dipping time and that the casting rate increases if the sol concentration increases, the pore size of the support decreases or the gelling concentration decreases, are all in accordance with this slibcasting model.
193 citations
TL;DR: The experimental and theoretical results suggest that, in order to reduce effectively the average pore size of a membrane by a modification process, the membrane should have a rather uniform pore sizes distribution, or the modification process should be conducted under conditions which give a pore narrowing rate proportional to the poresize.
Abstract: Experimental results on pore size change of a microfiltration (MF) -alumina membrane and an ultrafiltration (UF) γ-alumina membrane after modification by chemical vapor deposition (CVD) of solid oxides in the membrane pores are presented and explained using the results of a theoretical analysis. With an approx. 10-fold reduction in permeability, the average pore size of the MF membrane is found to increase after CVD modification, due to its relatively broader initial pore size distribution with a small amount of large pores and due to the particular CVD conditions (heterogeneous deposition mechanism) which give a pore narrowing rate independent of pore size. The effective pore size of the UF membrane appears to remain unchanged after modification with an approx. 50-fold reduction in permeability, as a result of the slit-shaped pores of the γ-alumina film and the particular modification conditions. The experimental and theoretical results suggest that, in order to reduce effectively the average pore size of a membrane by a modification process, the membrane should have a rather uniform pore size distribution, or the modification process should be conducted under conditions which give a pore narrowing rate proportional to the pore size.
132 citations