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Preparation of surface modified porous membranes and their pervaporation properties
DESALINATION ELSEVIER
Desalination
148 (2002) 17-18 www.elsevier.com/locate/desal
Preparation of surface modified porous membranes and their pervaporation properties Tetsuro Jin*, Koji Kuraoka, Tetsuo Yazawa National Institute of Advanced Industrial Science & Technology, AIST Kansai, Special Division of Green Life Technology, Ecoglass Research Group, l-8-31 Midorigaoka, I&da, Osaka 563-8577, Japan e-mail: [email protected] Received 4 February 2002; accepted 13 March 2002
Abstract
The porous glass membrane modified by hydrophobic organocompound such as octadecyldimethylchlorosilane was prepared and methanol separation using this membrane was attempted to carry out by pervaporation technique. Keywords:
Porous membranes;
Pervaporation
1. Introduction Much attention has been focused recently on the development of methanol as alternative petroleum by semiconductor photocatalyst such as TiO;! and artificial photosynthesis using CO* and H20. Methanol synthesized by those techniques was included a large amount of HZ0 *Corresponding
author
Presented at the International July 7-12, 2002 0011-9 164/02/$-
Congress on Membranes
(more than 95%), however, the water should be removed to the solution effectively using some techniques as an energy saving for practical use. On the other hand, the porous glass membrane which possesses a large amount of silanol group on the surface [l] can be modified by hydrophobic organinocompounds such as octadecyldimethylchlorosilane (ODS), heptadecafluoro- 1,1,2,2-tetrahydrodecyldimethylchlorosilane (HDS), trimethylchlorosilane (TMS) and Membrane
See front matter 0 2002 Elsevier Science B.V.
PII: SO0 I1 -9 164(02)00646-X
Processes
All rights reserved
(ICOM), Toulouse, France,
7: Jin et al. /Desalination
and so on. In this study, those strong hydrophobic membranes were prepared and methanol separation using this membrane was attempted to carry out by pervaporation technique. 2. Methods Porous glass tubes (pore diameter ca. 4 nm) were prepared according to the procedure reported elsewhere [2]. The chemicals and reagents used this study were purchased either from Wako Pure Chemical Industries Limited, or Aldrich Inc. and used with out further purification. The porous glass after drying at 443K for 3 h in vacua was treated with a hydrophobic surface modifier by refluxing it in toluene for 20-60 h. The porous glass was finally refluxed only in toluene alone for another 24 h to remove any chemicals to porous substrate. The pervaporation measurements using an aqueous methanol solution as a feed were performed on a standard pervaporation apparatus. Liquid nitrogen was used as a cooling agent for the cold trap. The composition of the feed and the permeate were determined by gas chromatography. Flux and separation factor a (MethanoVHzO) were calculated as following equations. Flux (kg/m2h) = [weight of permeate]/ ([membrane area] x [permeation time]) separation factor a (methanol/HzO) = (Y+!lY/$(&&) where X& and YA,Hare the volume fractions of methanol and Hz0 in the feed and the permeate, respectively. After the surface modification of porous glass, the pore size distribution of the porous glass membranes were measured by nitrogen absorption isotherm.
18
148 (2002) 17-18
3. Results From this result, one peak was observed at ca. 1.9 nm on the original porous glass without surface modification and the peak on the surface modification glass by ODS was no observed after the treatment for more than 60 h. This showed that the surface and pores of the substrate were effectively modified by the organic modifier. Furthermore, the pervaporation measurements using the surface modified porous glass by ODS, HDS and TMS was carried out at room temperature. These separation factors were summarized in Table 1.
Table 1 Methanol separation properties by TMS, ODS and HDS modified glass membrane at room temperature Separation factor cx
Flux, Q (x 1O-*kg/m*h)
TMS
15
3.7
ODS HDS
50
18.1
67
15.5
Modifiers
further experiments by using Thus, membrane modified by other kinds of now are organomodifiers hydrophobic performed for considering the detail mechanism of methanol separation. References [l] T. Yazawa, Membrane, 20 (1995) 183. [2] T. Yazawa and H. Tanaka, Ceram. Trans., (1993) 213.
31
Desalination
148 (2002) 17-18 www.elsevier.com/locate/desal
Preparation of surface modified porous membranes and their pervaporation properties Tetsuro Jin*, Koji Kuraoka, Tetsuo Yazawa National Institute of Advanced Industrial Science & Technology, AIST Kansai, Special Division of Green Life Technology, Ecoglass Research Group, l-8-31 Midorigaoka, I&da, Osaka 563-8577, Japan e-mail: [email protected] Received 4 February 2002; accepted 13 March 2002
Abstract
The porous glass membrane modified by hydrophobic organocompound such as octadecyldimethylchlorosilane was prepared and methanol separation using this membrane was attempted to carry out by pervaporation technique. Keywords:
Porous membranes;
Pervaporation
1. Introduction Much attention has been focused recently on the development of methanol as alternative petroleum by semiconductor photocatalyst such as TiO;! and artificial photosynthesis using CO* and H20. Methanol synthesized by those techniques was included a large amount of HZ0 *Corresponding
author
Presented at the International July 7-12, 2002 0011-9 164/02/$-
Congress on Membranes
(more than 95%), however, the water should be removed to the solution effectively using some techniques as an energy saving for practical use. On the other hand, the porous glass membrane which possesses a large amount of silanol group on the surface [l] can be modified by hydrophobic organinocompounds such as octadecyldimethylchlorosilane (ODS), heptadecafluoro- 1,1,2,2-tetrahydrodecyldimethylchlorosilane (HDS), trimethylchlorosilane (TMS) and Membrane
See front matter 0 2002 Elsevier Science B.V.
PII: SO0 I1 -9 164(02)00646-X
Processes
All rights reserved
(ICOM), Toulouse, France,
7: Jin et al. /Desalination
and so on. In this study, those strong hydrophobic membranes were prepared and methanol separation using this membrane was attempted to carry out by pervaporation technique. 2. Methods Porous glass tubes (pore diameter ca. 4 nm) were prepared according to the procedure reported elsewhere [2]. The chemicals and reagents used this study were purchased either from Wako Pure Chemical Industries Limited, or Aldrich Inc. and used with out further purification. The porous glass after drying at 443K for 3 h in vacua was treated with a hydrophobic surface modifier by refluxing it in toluene for 20-60 h. The porous glass was finally refluxed only in toluene alone for another 24 h to remove any chemicals to porous substrate. The pervaporation measurements using an aqueous methanol solution as a feed were performed on a standard pervaporation apparatus. Liquid nitrogen was used as a cooling agent for the cold trap. The composition of the feed and the permeate were determined by gas chromatography. Flux and separation factor a (MethanoVHzO) were calculated as following equations. Flux (kg/m2h) = [weight of permeate]/ ([membrane area] x [permeation time]) separation factor a (methanol/HzO) = (Y+!lY/$(&&) where X& and YA,Hare the volume fractions of methanol and Hz0 in the feed and the permeate, respectively. After the surface modification of porous glass, the pore size distribution of the porous glass membranes were measured by nitrogen absorption isotherm.
18
148 (2002) 17-18
3. Results From this result, one peak was observed at ca. 1.9 nm on the original porous glass without surface modification and the peak on the surface modification glass by ODS was no observed after the treatment for more than 60 h. This showed that the surface and pores of the substrate were effectively modified by the organic modifier. Furthermore, the pervaporation measurements using the surface modified porous glass by ODS, HDS and TMS was carried out at room temperature. These separation factors were summarized in Table 1.
Table 1 Methanol separation properties by TMS, ODS and HDS modified glass membrane at room temperature Separation factor cx
Flux, Q (x 1O-*kg/m*h)
TMS
15
3.7
ODS HDS
50
18.1
67
15.5
Modifiers
further experiments by using Thus, membrane modified by other kinds of now are organomodifiers hydrophobic performed for considering the detail mechanism of methanol separation. References [l] T. Yazawa, Membrane, 20 (1995) 183. [2] T. Yazawa and H. Tanaka, Ceram. Trans., (1993) 213.
31