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Preparation and characterization of low cost tubular ceramic support membranes using sawdust as a pore-former
Materials Letters 110 (2013) 152–155
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation and characterization of low cost tubular ceramic support membranes using sawdust as a pore-former Sujoy Bose, Chandan Das n Department of Chemical Engineering, Indian Institute of Technology, Guwahati, Assam 781039, India
art ic l e i nf o
a b s t r a c t
Article history: Received 7 June 2013 Accepted 4 August 2013 Available online 14 August 2013
The manufacturing of low cost ceramic tubular support membrane via dry compaction method using cheap material, namely, sawdust along with kaolin and feldspar was demonstrated in this study. Thermogravimetric analysis, particle size distribution, image analysis, volumetric porosity and gas permeation experiments, acid–alkali test and three-point bend test were studied to characterize the fabricated membrane, systematically. The support membrane was casted on a cylindrical mold and sintered at three different temperatures of 550, 700 and 850 1C. The average pore diameter of the membrane was decreased with increasing temperature. Adversely, the membrane porosity was increased with increasing temperature. The chemical and mechanical stability of the fabricated membrane were appreciable. Based on raw materials, energy consumption and mold preparation, the cost of the support membrane was estimated as around $250/m2. Hereafter, these low cost support membranes with good physical and chemical properties may be applied for the processing of value-aided products. & 2013 Elsevier B.V. All rights reserved.
Keywords: Biomimetic Ceramics Porous materials Phase transformation Thermal analysis
1. Introduction
2. Materials and methods
Catalytic membrane reactors which pursued two distinct functions, i.e., reaction and separation, were prepared and broadly used for several applications. The performance of a catalytic membrane was related to its support configuration and surface texture which was quite challenging and expensive in respective of raw materials [1,2]. Therefore, much attention had been made to plan a novel route using low-cost raw materials for the fabrication of support of catalytic membrane reactors. Tubular support membranes were used widely in catalytic membrane reactors for its ability to handle process streams with highly viscous solids and to minimize fouling by mechanical cleaning due to its small area per unit volume. Herein, we report the fabrication of low-cost tubular ceramic membrane via dry compaction method using kaolin, feldspar as the source materials and sawdust as pore-former and its characterization. The present work has two significant points which make this work novel. First, sawdust is adopted as a pore-former for the first time for the support of tubular catalytic membrane reactor. Second, the combination of sawdust and kaolin is limited among the conventional kaolin based membranes.
Synthesis: The sawdust particles were screened, mixed with kaolin (Loba Chemie), quartz (Hi-Media) and feldspar (National Chemicals) maintaining different compositions (Table 1) in mixer machine and grinded using ceramic mortar. The compositions were selected on trial basis to get the best results in terms of morphological properties, chemical and mechanical stability and preparation cost. The grinded mixture was placed into a cylindrical mold (50 mm outer diameter and height; 10 mm thickness) and applied 9807 kPa pressure by hydraulic press, removed and dried at room temperature for 24 h. After that, it was dried at 100 1C for 12 h in a muffle furnace followed by heating at 250 1C for 24 h. Then the membrane was heated from 250 1C to the desired temperature at a heating rate of 2 1C/min and kept for 5 h, cooled and removed. Characterization: The fabricated membrane was characterized by thermogravimetric analysis (TGA/SDTA 851s, ), X-ray diffraction study (Bruker D8 Advanced series), field emission scanning electron microscopy (Zeiss) and Energy-dispersive X-ray spectroscopy (LEO 1430VPs), particle size distribution (Malvern Mastersizer 2000). The volumetric porosity was calculated from the following equation: εv ¼ ðW 2 W 1 Þ=ρH2 O V
n
Corresponding author. Tel.: +91 361 258 2268; fax: +91 361 258 2291. E-mail address: [email protected] (C. Das).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.08.019
ð1Þ
where W2, W1, ρH2 O and V were the weights of the wet and dry membrane samples, the density of the deionized water and the volume of the fabricated membrane respectively. The gas
S. Bose, C. Das / Materials Letters 110 (2013) 152–155
2
Table 1 Composition of raw materials used for the preparation of ceramic support membrane.
Kaolin Quartz Saw dust
Feldspar
40 40 30 40 50 50
10 20 40 25 0 25
20 30 10 25 25 0
30 10 20 10 25 25
80
-2
(e) (d) (a) Kaolin
60
-4
(b) Quartz (c) Saw dust (d) Feldspar
40
-6 (f)
(e) Mixture of raw materials in SM6
-8
(f) Mixture of
20
raw materials in
(c)
SM6 (DTA)
0
permeation data was utilized to estimate two vital membrane characteristics namely, average pore radius (rg) and effective porosity (ε/q2) according to the following expression [3] ! r ε r 2g 1 ε g v þ 1:6 P ð2Þ k ¼ 2:133 l q2 l η q2
0 (a)
Operating pressure (kPa)
9807
(b)
DTA (mV)
SM1 SM2 SM3 SM4 SM5 SM6
Composition dry basis (wt%)
100
Weight loss (%)
Name of membrane support
153
0
-10
825°C
200
400
600
800
Temperature (°C) Fig. 1. TGA/DTA plot of four individual raw materials and SM6 decomposed in presence of nitrogen atmosphere at 10 1C/min.
6
where, P was the average pressure on the membrane (kPa), v was the molecular mean velocity of the operating gas (m/s), l was the pore length (m), q was the tortuosity factor of the membrane, η was the viscosity of the gas (Pa s), k was the effective permeability (m/s). The values of the slope and intercept obtained from the graph were used to evaluate the pore diameter and porosity of the membrane. Acid–alkali test of all the fabricated membranes was evaluated by exposing the membrane to the acid (Conc. HCl, pH 2) and alkali (NaOH, pH 12) solution, purchased from M/s Merck India Pvt. Ltd. The mechanical strength of the membrane was tested using three point bend test (Universal Tensile Test Machine, Deepak Polyplast Pvt. Ltd., India).
SM1 SM2 SM3 SM4 SM5 SM6
5
Volume (%)
4
3
2
1
0 0.01
3. Results and discussion
0.1
1
10
100
1000
Particle size (µm)
Fig. 1a–d demonstrated the weight loss of individual raw materials with respect to temperature. Fig. 1e displayed total 19% weight loss related to removal of moisture, decomposition of hemicellulose, cellulose and lignin and the transformation of kaolinite to metakaolinite, confirmed by the DTA curve (Fig. 1f). The porosity and the average pore size of the membrane were controlled by particle size of the raw materials. As shown in Fig. 2, the majority of the particles of the sample mixtures were between 1 and 30 mm. The average particle size of SM6 was around 12.33 mm, highest among the other combinations, points to slightly dense structure with lower temperature, satisfied the porosity data obtained from volumetric technique and gas permeability test. The volumetric porosity of different membranes sintered at 550, 700 and 850 1C, was dependent on three factors involving particle size of raw materials, decomposition of sawdust, and sintering temperature. The porosity of SM6 varied in the range of 19% to 36%, increased with increasing temperature due to the decomposition of sawdust and its higher particle size. Higher the amount of sawdust, higher was the porosity due to loose densification between particles. Calcination of SM6 at 850 1C (Fig. 3a) did not show any strong peak as compared to the un-calcined sample mixture, indicating an amorphous texture with no phase change above 550 1C and the presence of metakaolinite. Membrane sintered at 550 1C indicated the presence of ligno-cellulosic material and graphite. The sample phase was confirmed by the comparison between the XRD patterns of sintered samples and raw kaolinite (Fig. 3b).
Fig. 2. Particle size distribution for different sample mixtures.
Fig. 4(a1, a2, a3) presented the FESEM images of SM6 membrane calcined at 550, 700 and 850 1C. The various surface structures with change in temperature were influenced by the decomposition of sawdust. Fig. 4(a1 and a2) indicated a crystalline dense structure due to negligible change in particle-particle interaction. However, large agglomerated particles resembled to amorphous texture, as shown in Fig. 4(a3). Pore size distribution was evaluated from the FESEM images using ImageJ software, presented in Fig. 4(b). The pores of the membranes were assumed to be cylindrical in nature to calculate the area average pore diameters (ds). The maximum number of pores (60%) for all sintering temperatures was in the range of 0.3–0.8 μm. " # 2 0:5 ∑ni¼ 1 ni di ð3Þ ds ¼ ∑ni¼ 1 ni where, n was the number of pores, di was the pore diameter of the i-th pore (μm). The average pore diameters of the SM6 membranes were calculated as 0.35, 0.25 and 0.19 μm with increasing temperature. The gas permeation study showed the permeance of the SM6 membrane sintered at 550, 700 and 850 1C are 1.70 10 3, 3.675 10 3 and 3.71 10 3 m3 m 2 s 1 kPa 1 using Eq. (4). p¼
Q SΔP
ð4Þ
154
S. Bose, C. Das / Materials Letters 110 (2013) 152–155
Fig. 3. (a) X-ray diffraction patterns of the sample mixture sintered at different temperatures 1: kaolinite (PDF-00-001-0527) 2: feldspar (PDF-00-031-0965) 3: graphite (PDF-01-074-2330) 4: cellulose (PDF-00-003-0192) 5: xylitol (PDF-00-032-1981); (b) XRD diagram of Kaolin powder 1: Kaolinite (PDF-00-001-0527).
Number of pores (%)
35
Effective permeability factor (k), m/s
40 550°C 700°C 850°C
30 25 20 15 10 5 0
0
1
2
3
4
0.22 0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02
550°C 700°C 850°C
0
10
20
30
40
50
60
70
Average pressure (kPa)
Pore diameter (µm)
Fig. 4. (a) FESEM micrographs of SM6 sintered at (a1) 550 1C (a2) 700 1C and (a3) 850 1C. (b) Pore size distribution of the fabricated SM6 membrane sintered at three different temperatures as determined from FESEM images. (c) Effect of pressure on gas permeability for membranes sintered at different temperatures.
where, S was the permeable area of the membrane (m2), Q was the volumetric flow rate (m3/s). Porosity and pore size of SM6 were calculated assuming tortuosity factor one, in the range of 14–34% and 0.38–0.13 mm, respectively, by using Eq. (2) and the values of slope were obtained from Fig. 4(c). The obtained porosity was close to the reported value of kaolin based membranes and could be appropriate for different microfiltration applications like waste water treatment, bacterial separation, etc. [4]. An increase in porosity of SM6 membranes was observed during both alkali and acid tests. The porosity values were observed as 21%, 27%, 37% and 20%, 27%, 37% with increasing temperature during alkali and acid test, respectively. The residual hemicellulose and most part of the lignin were extracted and oxidized by alkali and acids, respectively, provided an increase in porosity. No significant compositional change was observed after acid and alkali test compared to that of SM6 membrane before acid-alkali test, indicated by EDX study (see Supplementary material). The flexural strength of SM6 membranes was observed as 2 MPa at 850 1C using ASTM standard test (ASTM D790) without
any binder. As the number of contact between the particles as well as the specific surface were reduced due to higher particle size and absence of binder, the flexural strength of the solid ceramics was less compared to the reported value of kaolin based membrane having two different binders in their composition [5]. Based on the unit cost of raw materials and energy cost for sintering process, the manufacturing cost of the SM6 membrane was evaluated as around $250/m2 including membrane mold preparation charge, cheapest among all the combinations. The evaluated cost of the membranes was close to the cost of polymeric membranes and higher than disk shaped ceramic membranes made from low cost raw materials.
4. Conclusions In summary, the estimated cost ( $250/m2) tubular membrane was less compared to the membrane available in market. Sawdust was a of commonly used pore-formers which not only
of the prepared tubular shaped great substitute provided a high
S. Bose, C. Das / Materials Letters 110 (2013) 152–155
porosity as 36% but also approved a new combination of composite material with good morphology, mechanical and chemical stability. Acknowledgment The authors are thankful to Central Instruments Facility (CIF), IIT Guwahati for their support. Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2013.08.019.
155
References [1] Neomagus HWJP, Saracco G, Versteeg A. Fixed bed barrier reactor with separate feed of reactants. Chemical Engineering Communications 2001;184:49–69. [2] Pina MP, Menendez M, Santamaría J. The Knudsen diffusion catalytic membrane reactor: an efficient contactor for the combustion of volatile organic compounds. Applied Catalysis B: Environmental 1996;11:L19–27. [3] Marchese J, Pagliero CL. Characterization of asymmetric polysulphone membranes for gas separation. Gas Separation and Purification 1991;5:215–21. [4] Vasanth D, Pugazhenthi G, Uppaaluri R. Fabrication and properties of low cost ceramic microfiltration membranes for separation of oil and bacteria from its solution. Journal of Membrane Science 2011;379:154–63. [5] Nandi BK, Uppaaluri R, Purkait MK. Preparation and characterization of low cost ceramic membranes for micro-filtration applications. Applied Clay Science 2008;42:102–10.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation and characterization of low cost tubular ceramic support membranes using sawdust as a pore-former Sujoy Bose, Chandan Das n Department of Chemical Engineering, Indian Institute of Technology, Guwahati, Assam 781039, India
art ic l e i nf o
a b s t r a c t
Article history: Received 7 June 2013 Accepted 4 August 2013 Available online 14 August 2013
The manufacturing of low cost ceramic tubular support membrane via dry compaction method using cheap material, namely, sawdust along with kaolin and feldspar was demonstrated in this study. Thermogravimetric analysis, particle size distribution, image analysis, volumetric porosity and gas permeation experiments, acid–alkali test and three-point bend test were studied to characterize the fabricated membrane, systematically. The support membrane was casted on a cylindrical mold and sintered at three different temperatures of 550, 700 and 850 1C. The average pore diameter of the membrane was decreased with increasing temperature. Adversely, the membrane porosity was increased with increasing temperature. The chemical and mechanical stability of the fabricated membrane were appreciable. Based on raw materials, energy consumption and mold preparation, the cost of the support membrane was estimated as around $250/m2. Hereafter, these low cost support membranes with good physical and chemical properties may be applied for the processing of value-aided products. & 2013 Elsevier B.V. All rights reserved.
Keywords: Biomimetic Ceramics Porous materials Phase transformation Thermal analysis
1. Introduction
2. Materials and methods
Catalytic membrane reactors which pursued two distinct functions, i.e., reaction and separation, were prepared and broadly used for several applications. The performance of a catalytic membrane was related to its support configuration and surface texture which was quite challenging and expensive in respective of raw materials [1,2]. Therefore, much attention had been made to plan a novel route using low-cost raw materials for the fabrication of support of catalytic membrane reactors. Tubular support membranes were used widely in catalytic membrane reactors for its ability to handle process streams with highly viscous solids and to minimize fouling by mechanical cleaning due to its small area per unit volume. Herein, we report the fabrication of low-cost tubular ceramic membrane via dry compaction method using kaolin, feldspar as the source materials and sawdust as pore-former and its characterization. The present work has two significant points which make this work novel. First, sawdust is adopted as a pore-former for the first time for the support of tubular catalytic membrane reactor. Second, the combination of sawdust and kaolin is limited among the conventional kaolin based membranes.
Synthesis: The sawdust particles were screened, mixed with kaolin (Loba Chemie), quartz (Hi-Media) and feldspar (National Chemicals) maintaining different compositions (Table 1) in mixer machine and grinded using ceramic mortar. The compositions were selected on trial basis to get the best results in terms of morphological properties, chemical and mechanical stability and preparation cost. The grinded mixture was placed into a cylindrical mold (50 mm outer diameter and height; 10 mm thickness) and applied 9807 kPa pressure by hydraulic press, removed and dried at room temperature for 24 h. After that, it was dried at 100 1C for 12 h in a muffle furnace followed by heating at 250 1C for 24 h. Then the membrane was heated from 250 1C to the desired temperature at a heating rate of 2 1C/min and kept for 5 h, cooled and removed. Characterization: The fabricated membrane was characterized by thermogravimetric analysis (TGA/SDTA 851s, ), X-ray diffraction study (Bruker D8 Advanced series), field emission scanning electron microscopy (Zeiss) and Energy-dispersive X-ray spectroscopy (LEO 1430VPs), particle size distribution (Malvern Mastersizer 2000). The volumetric porosity was calculated from the following equation: εv ¼ ðW 2 W 1 Þ=ρH2 O V
n
Corresponding author. Tel.: +91 361 258 2268; fax: +91 361 258 2291. E-mail address: [email protected] (C. Das).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.08.019
ð1Þ
where W2, W1, ρH2 O and V were the weights of the wet and dry membrane samples, the density of the deionized water and the volume of the fabricated membrane respectively. The gas
S. Bose, C. Das / Materials Letters 110 (2013) 152–155
2
Table 1 Composition of raw materials used for the preparation of ceramic support membrane.
Kaolin Quartz Saw dust
Feldspar
40 40 30 40 50 50
10 20 40 25 0 25
20 30 10 25 25 0
30 10 20 10 25 25
80
-2
(e) (d) (a) Kaolin
60
-4
(b) Quartz (c) Saw dust (d) Feldspar
40
-6 (f)
(e) Mixture of raw materials in SM6
-8
(f) Mixture of
20
raw materials in
(c)
SM6 (DTA)
0
permeation data was utilized to estimate two vital membrane characteristics namely, average pore radius (rg) and effective porosity (ε/q2) according to the following expression [3] ! r ε r 2g 1 ε g v þ 1:6 P ð2Þ k ¼ 2:133 l q2 l η q2
0 (a)
Operating pressure (kPa)
9807
(b)
DTA (mV)
SM1 SM2 SM3 SM4 SM5 SM6
Composition dry basis (wt%)
100
Weight loss (%)
Name of membrane support
153
0
-10
825°C
200
400
600
800
Temperature (°C) Fig. 1. TGA/DTA plot of four individual raw materials and SM6 decomposed in presence of nitrogen atmosphere at 10 1C/min.
6
where, P was the average pressure on the membrane (kPa), v was the molecular mean velocity of the operating gas (m/s), l was the pore length (m), q was the tortuosity factor of the membrane, η was the viscosity of the gas (Pa s), k was the effective permeability (m/s). The values of the slope and intercept obtained from the graph were used to evaluate the pore diameter and porosity of the membrane. Acid–alkali test of all the fabricated membranes was evaluated by exposing the membrane to the acid (Conc. HCl, pH 2) and alkali (NaOH, pH 12) solution, purchased from M/s Merck India Pvt. Ltd. The mechanical strength of the membrane was tested using three point bend test (Universal Tensile Test Machine, Deepak Polyplast Pvt. Ltd., India).
SM1 SM2 SM3 SM4 SM5 SM6
5
Volume (%)
4
3
2
1
0 0.01
3. Results and discussion
0.1
1
10
100
1000
Particle size (µm)
Fig. 1a–d demonstrated the weight loss of individual raw materials with respect to temperature. Fig. 1e displayed total 19% weight loss related to removal of moisture, decomposition of hemicellulose, cellulose and lignin and the transformation of kaolinite to metakaolinite, confirmed by the DTA curve (Fig. 1f). The porosity and the average pore size of the membrane were controlled by particle size of the raw materials. As shown in Fig. 2, the majority of the particles of the sample mixtures were between 1 and 30 mm. The average particle size of SM6 was around 12.33 mm, highest among the other combinations, points to slightly dense structure with lower temperature, satisfied the porosity data obtained from volumetric technique and gas permeability test. The volumetric porosity of different membranes sintered at 550, 700 and 850 1C, was dependent on three factors involving particle size of raw materials, decomposition of sawdust, and sintering temperature. The porosity of SM6 varied in the range of 19% to 36%, increased with increasing temperature due to the decomposition of sawdust and its higher particle size. Higher the amount of sawdust, higher was the porosity due to loose densification between particles. Calcination of SM6 at 850 1C (Fig. 3a) did not show any strong peak as compared to the un-calcined sample mixture, indicating an amorphous texture with no phase change above 550 1C and the presence of metakaolinite. Membrane sintered at 550 1C indicated the presence of ligno-cellulosic material and graphite. The sample phase was confirmed by the comparison between the XRD patterns of sintered samples and raw kaolinite (Fig. 3b).
Fig. 2. Particle size distribution for different sample mixtures.
Fig. 4(a1, a2, a3) presented the FESEM images of SM6 membrane calcined at 550, 700 and 850 1C. The various surface structures with change in temperature were influenced by the decomposition of sawdust. Fig. 4(a1 and a2) indicated a crystalline dense structure due to negligible change in particle-particle interaction. However, large agglomerated particles resembled to amorphous texture, as shown in Fig. 4(a3). Pore size distribution was evaluated from the FESEM images using ImageJ software, presented in Fig. 4(b). The pores of the membranes were assumed to be cylindrical in nature to calculate the area average pore diameters (ds). The maximum number of pores (60%) for all sintering temperatures was in the range of 0.3–0.8 μm. " # 2 0:5 ∑ni¼ 1 ni di ð3Þ ds ¼ ∑ni¼ 1 ni where, n was the number of pores, di was the pore diameter of the i-th pore (μm). The average pore diameters of the SM6 membranes were calculated as 0.35, 0.25 and 0.19 μm with increasing temperature. The gas permeation study showed the permeance of the SM6 membrane sintered at 550, 700 and 850 1C are 1.70 10 3, 3.675 10 3 and 3.71 10 3 m3 m 2 s 1 kPa 1 using Eq. (4). p¼
Q SΔP
ð4Þ
154
S. Bose, C. Das / Materials Letters 110 (2013) 152–155
Fig. 3. (a) X-ray diffraction patterns of the sample mixture sintered at different temperatures 1: kaolinite (PDF-00-001-0527) 2: feldspar (PDF-00-031-0965) 3: graphite (PDF-01-074-2330) 4: cellulose (PDF-00-003-0192) 5: xylitol (PDF-00-032-1981); (b) XRD diagram of Kaolin powder 1: Kaolinite (PDF-00-001-0527).
Number of pores (%)
35
Effective permeability factor (k), m/s
40 550°C 700°C 850°C
30 25 20 15 10 5 0
0
1
2
3
4
0.22 0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02
550°C 700°C 850°C
0
10
20
30
40
50
60
70
Average pressure (kPa)
Pore diameter (µm)
Fig. 4. (a) FESEM micrographs of SM6 sintered at (a1) 550 1C (a2) 700 1C and (a3) 850 1C. (b) Pore size distribution of the fabricated SM6 membrane sintered at three different temperatures as determined from FESEM images. (c) Effect of pressure on gas permeability for membranes sintered at different temperatures.
where, S was the permeable area of the membrane (m2), Q was the volumetric flow rate (m3/s). Porosity and pore size of SM6 were calculated assuming tortuosity factor one, in the range of 14–34% and 0.38–0.13 mm, respectively, by using Eq. (2) and the values of slope were obtained from Fig. 4(c). The obtained porosity was close to the reported value of kaolin based membranes and could be appropriate for different microfiltration applications like waste water treatment, bacterial separation, etc. [4]. An increase in porosity of SM6 membranes was observed during both alkali and acid tests. The porosity values were observed as 21%, 27%, 37% and 20%, 27%, 37% with increasing temperature during alkali and acid test, respectively. The residual hemicellulose and most part of the lignin were extracted and oxidized by alkali and acids, respectively, provided an increase in porosity. No significant compositional change was observed after acid and alkali test compared to that of SM6 membrane before acid-alkali test, indicated by EDX study (see Supplementary material). The flexural strength of SM6 membranes was observed as 2 MPa at 850 1C using ASTM standard test (ASTM D790) without
any binder. As the number of contact between the particles as well as the specific surface were reduced due to higher particle size and absence of binder, the flexural strength of the solid ceramics was less compared to the reported value of kaolin based membrane having two different binders in their composition [5]. Based on the unit cost of raw materials and energy cost for sintering process, the manufacturing cost of the SM6 membrane was evaluated as around $250/m2 including membrane mold preparation charge, cheapest among all the combinations. The evaluated cost of the membranes was close to the cost of polymeric membranes and higher than disk shaped ceramic membranes made from low cost raw materials.
4. Conclusions In summary, the estimated cost ( $250/m2) tubular membrane was less compared to the membrane available in market. Sawdust was a of commonly used pore-formers which not only
of the prepared tubular shaped great substitute provided a high
S. Bose, C. Das / Materials Letters 110 (2013) 152–155
porosity as 36% but also approved a new combination of composite material with good morphology, mechanical and chemical stability. Acknowledgment The authors are thankful to Central Instruments Facility (CIF), IIT Guwahati for their support. Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2013.08.019.
155
References [1] Neomagus HWJP, Saracco G, Versteeg A. Fixed bed barrier reactor with separate feed of reactants. Chemical Engineering Communications 2001;184:49–69. [2] Pina MP, Menendez M, Santamaría J. The Knudsen diffusion catalytic membrane reactor: an efficient contactor for the combustion of volatile organic compounds. Applied Catalysis B: Environmental 1996;11:L19–27. [3] Marchese J, Pagliero CL. Characterization of asymmetric polysulphone membranes for gas separation. Gas Separation and Purification 1991;5:215–21. [4] Vasanth D, Pugazhenthi G, Uppaaluri R. Fabrication and properties of low cost ceramic microfiltration membranes for separation of oil and bacteria from its solution. Journal of Membrane Science 2011;379:154–63. [5] Nandi BK, Uppaaluri R, Purkait MK. Preparation and characterization of low cost ceramic membranes for micro-filtration applications. Applied Clay Science 2008;42:102–10.