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Modified porous glass with silane coupling reagents as an ion-exchange membrane
Thin Solid Films, 182 (1989) L 13 L 16
L13
Letter
Modified porous glass with silane coupling reagents as an ion-exchange membrane T. H. CHIANG, A. NAKAMURA AND F. TODA
Department of Bioengineering and Bioscience, Faculo' of Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152 (Japan) Received June 28, 1989; accepted September 6, 1989)
1. Introduction A new method for the construction of monolayer built-up film, different in principle from the classical Langmuir-Blodgett technique, has been described by Sagiv and co-workers 1. We have reported the modification of porous glass with N-2-aminoethyl-3-aminopropyl group as a cation type ion-exchange membrane 2. In this letter, we prepared the anion type ion-exchange membrane by chemical bonding the succinic anhydride with the amino groups on the modified porous glass surface, and compared some of its properties with those of the original cation type ion-exchange membrane. We also found Cu(II) ion forming complex with N-2-aminoethyl-3aminopropyl groups and moving on the modified porous glass surface, when two CuSO4 solution of different concentration are located in both compartments (Fig. 1). 2. Experimental details The methods of cleaning and modifying porous glass (average pore radius of 20A, Corning 7930) surface was the same as has been described 2. The porous glass modified with (3-(2-aminoethylamino)propyl)trimethoxysilane(AEAPS) or 3aminopropyltrimethoxysilane(APS) was then reacted with succinic anhydride (Scheme 1).
PG Si
(CH30)3 S i(Cl-Iz)3N lq~ OH in water, r.t. ~
Si
OCI 13 ] O - - Si--(CI-12)NH 2
I OCH3 Succinic anhydrid~ in pyridine, r.t.
Si
O --Si
I I
OCH3
(CH2)3N I1-- C .--CH2 -- CH2---.C-X)O-
OCt] 3
ii
O
Scheme l. The modificationof APS membranesurfacewith succinicanhydride. 0040-6090/89/$3.50
© ElsevierSequoia/Printedin The Netherlands
LI4
I.ETTERS
A p H m e t e r e q u i p p e d w i t h t w o reference e l e c t r o d e s , w h i c h had the a r g e n t u m c h l o r i d e e l e c t r o d e as the i n t e r n a l e l e c t r o d e was used to m e a s u r e the m e m b r a n e p o t e n t i a l (Fig. 1) Porous Glass
Fig. 1. Apparatus for nleasurement of nlember potential. Electrolyte concentration m compartment o:CoM: in compartment d:CdM. Electrode immersed in each cell is Ag I AgCI I sat. KCI reference electrode.
3. Resuhs and discussion Figure 2 shows apparent transport number across modified membranes and u n m o d i f i e d p o r o u s glass. T h e c o n c e n t r a t i o n of KC1 in the o c o m p a r t m e n t is 0.01 M, a n d t h a t in the d c o m p a r t m e n t is C d M. T h e m e m b r a n e , w h i c h is m o d i f i e d w i t h 313,, A E A P S or A P S s o l u t i o n , s h o w s a n i o n - s e l e c t i v e p r o p e r t i e s . It was d u e to the fact t h a t the a m i n o g r o u p s of the A E A P S - o r A P S - m o d i f i e d m e m b r a n e s ' surface was 1.0 0.9 0.8 0.7 0.6 ~-' 0.5 0.4 0.3 0.2 0.1 0
3
-2
1 0 tog Cd Fig. 2. [1, Porous glass modified with 3"o AEAPS solution: C), porous glass modilied with 3{}i,APS solution; O, unmodified porous glass: I , AEA PS-moditied membrane modified with succinic anhydride: A, APS-moditied membrane modified with succinic anhydride.
LETTERS
L15
protonated. When these modified membranes are further modified with succinic anhydride, we get cation-selective membranes. In this case, it was due to the dissociated carboxyl groups ( C O 0 - ) (Scheme 1) on the modified membranes' surface. Furthermore, the AEAPA membrane, which is modified with succinic anhydride shows cation-selective properties. It means that both of the primary and the secondary amino groups are reacted with succinic anhydride. 1.0 0.9 0.80.70.6 AA
~_t
0.5 0.4 0.3 0.2 0.1 0 -3
I
-2
P
-1 log Cd
I
0
Fig. 3. C), APS-modified porous glass membrane treated with 0.1 M HCI solution; A, APS-modified porous glass membrane treated with 5 x 10- 3 M K O H solution; O, unmodified porous glass.
Figure 3 shows the effect of the surface condition of APS-modified porous glass membrane on the apparent transport number of chloride. KC1 concentration in the o compartment is 0.01M, and that in the d compartment is Cd M. As was already mentioned, the membrane, which is modified with 3% APS solution and has the protonated amino groups (NH 3 +) on the surface shows anion-selective properties. When this membrane is treated by 5 x 10-3M KOH, the protonated amino groups on the membrane surface are changed into amino groups (NH2). In this case, the net surface charge of the membrane was zero, and the membrane worked as a neutral membrane while the unmodified porous glass which has the dissociated silanol groups ( S i O ) on its surface shows cation-selective properties. When the surface properties of a modified membrane are compared with an unmodified membrane, it is clear that there are only a few unreacted free silanol groups on the porous glass surface. We have reported 2 that the Cu(II) ion forms complex with N-2-aminoethyl-3aminopropyl group on the AEAPS-modified membrane surface. In this letter we report that Cu(II) ion not only forms complex with N-2-aminoethyl-3-aminopropyl groups but moves on the modified porous glass surface when two CuSO 4 solutions of different concentrations are located in both compartments (Fig. 4). Figure 4 shows
L16
I.ETTERS
1.0
I r
J
i
i
--
0.9 F 0.8 0.7 , 0.6 I
~- 0.5 "o
0.4 0.3 0.2
I
0.1 [
L
0~ -3
-_
2
I
-1 Eog Cd
_± 0
1
Fig. 4. Apparent transport number of sulphate cs. log Cd plots of the data obtained in the AEAPSmoditied membrane system with cupric sulphate solution.
the apparent transport number of sulphate c s . log C d plots of the data obtained in the AEAPS-modified membrane system with a cupric sulphate solution. In this case, a 0.01M solution of cupric sulphate was located in the o compartment and another Ca M solution of the same kind of salt was in the d compartment. When the concentration of cupric sulphate is low (the left side of the Fig. 4), the protonation of amino groups precedes the formation of the complex Cu(II) ion with N-2aminoethyl-3-aminopropyl groups on the membrane surface, and this gives the membrane anion-selective properties. When the concentration of cupric sulphate is high (over 0.1M), the Cu(II) ion forms complex with N-2-aminoethyl-3aminopropyl groups on the membrane surface. Moreover, the modified membrane shows (the right side of the Fig. 4) cation-selective properties in spite of the protonated amino groups on the membrane surface. It means that the Cu(ll)ion not only forms complex with N-2-aminoethyl-3-aminopropyl groups but moves on the membrane surface. REFERENCES l 2
J. Sagiv, J. Am. ('/win. £'o~., 102 (1980) 92. T . H . Chiang. A. N a k a m u r a . K. Nishiza~sa and I:. Toda, ,\'IPPO,\' K,4U,4K[" K.41£'HI. l / (1987) 2O52.
L13
Letter
Modified porous glass with silane coupling reagents as an ion-exchange membrane T. H. CHIANG, A. NAKAMURA AND F. TODA
Department of Bioengineering and Bioscience, Faculo' of Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152 (Japan) Received June 28, 1989; accepted September 6, 1989)
1. Introduction A new method for the construction of monolayer built-up film, different in principle from the classical Langmuir-Blodgett technique, has been described by Sagiv and co-workers 1. We have reported the modification of porous glass with N-2-aminoethyl-3-aminopropyl group as a cation type ion-exchange membrane 2. In this letter, we prepared the anion type ion-exchange membrane by chemical bonding the succinic anhydride with the amino groups on the modified porous glass surface, and compared some of its properties with those of the original cation type ion-exchange membrane. We also found Cu(II) ion forming complex with N-2-aminoethyl-3aminopropyl groups and moving on the modified porous glass surface, when two CuSO4 solution of different concentration are located in both compartments (Fig. 1). 2. Experimental details The methods of cleaning and modifying porous glass (average pore radius of 20A, Corning 7930) surface was the same as has been described 2. The porous glass modified with (3-(2-aminoethylamino)propyl)trimethoxysilane(AEAPS) or 3aminopropyltrimethoxysilane(APS) was then reacted with succinic anhydride (Scheme 1).
PG Si
(CH30)3 S i(Cl-Iz)3N lq~ OH in water, r.t. ~
Si
OCI 13 ] O - - Si--(CI-12)NH 2
I OCH3 Succinic anhydrid~ in pyridine, r.t.
Si
O --Si
I I
OCH3
(CH2)3N I1-- C .--CH2 -- CH2---.C-X)O-
OCt] 3
ii
O
Scheme l. The modificationof APS membranesurfacewith succinicanhydride. 0040-6090/89/$3.50
© ElsevierSequoia/Printedin The Netherlands
LI4
I.ETTERS
A p H m e t e r e q u i p p e d w i t h t w o reference e l e c t r o d e s , w h i c h had the a r g e n t u m c h l o r i d e e l e c t r o d e as the i n t e r n a l e l e c t r o d e was used to m e a s u r e the m e m b r a n e p o t e n t i a l (Fig. 1) Porous Glass
Fig. 1. Apparatus for nleasurement of nlember potential. Electrolyte concentration m compartment o:CoM: in compartment d:CdM. Electrode immersed in each cell is Ag I AgCI I sat. KCI reference electrode.
3. Resuhs and discussion Figure 2 shows apparent transport number across modified membranes and u n m o d i f i e d p o r o u s glass. T h e c o n c e n t r a t i o n of KC1 in the o c o m p a r t m e n t is 0.01 M, a n d t h a t in the d c o m p a r t m e n t is C d M. T h e m e m b r a n e , w h i c h is m o d i f i e d w i t h 313,, A E A P S or A P S s o l u t i o n , s h o w s a n i o n - s e l e c t i v e p r o p e r t i e s . It was d u e to the fact t h a t the a m i n o g r o u p s of the A E A P S - o r A P S - m o d i f i e d m e m b r a n e s ' surface was 1.0 0.9 0.8 0.7 0.6 ~-' 0.5 0.4 0.3 0.2 0.1 0
3
-2
1 0 tog Cd Fig. 2. [1, Porous glass modified with 3"o AEAPS solution: C), porous glass modilied with 3{}i,APS solution; O, unmodified porous glass: I , AEA PS-moditied membrane modified with succinic anhydride: A, APS-moditied membrane modified with succinic anhydride.
LETTERS
L15
protonated. When these modified membranes are further modified with succinic anhydride, we get cation-selective membranes. In this case, it was due to the dissociated carboxyl groups ( C O 0 - ) (Scheme 1) on the modified membranes' surface. Furthermore, the AEAPA membrane, which is modified with succinic anhydride shows cation-selective properties. It means that both of the primary and the secondary amino groups are reacted with succinic anhydride. 1.0 0.9 0.80.70.6 AA
~_t
0.5 0.4 0.3 0.2 0.1 0 -3
I
-2
P
-1 log Cd
I
0
Fig. 3. C), APS-modified porous glass membrane treated with 0.1 M HCI solution; A, APS-modified porous glass membrane treated with 5 x 10- 3 M K O H solution; O, unmodified porous glass.
Figure 3 shows the effect of the surface condition of APS-modified porous glass membrane on the apparent transport number of chloride. KC1 concentration in the o compartment is 0.01M, and that in the d compartment is Cd M. As was already mentioned, the membrane, which is modified with 3% APS solution and has the protonated amino groups (NH 3 +) on the surface shows anion-selective properties. When this membrane is treated by 5 x 10-3M KOH, the protonated amino groups on the membrane surface are changed into amino groups (NH2). In this case, the net surface charge of the membrane was zero, and the membrane worked as a neutral membrane while the unmodified porous glass which has the dissociated silanol groups ( S i O ) on its surface shows cation-selective properties. When the surface properties of a modified membrane are compared with an unmodified membrane, it is clear that there are only a few unreacted free silanol groups on the porous glass surface. We have reported 2 that the Cu(II) ion forms complex with N-2-aminoethyl-3aminopropyl group on the AEAPS-modified membrane surface. In this letter we report that Cu(II) ion not only forms complex with N-2-aminoethyl-3-aminopropyl groups but moves on the modified porous glass surface when two CuSO 4 solutions of different concentrations are located in both compartments (Fig. 4). Figure 4 shows
L16
I.ETTERS
1.0
I r
J
i
i
--
0.9 F 0.8 0.7 , 0.6 I
~- 0.5 "o
0.4 0.3 0.2
I
0.1 [
L
0~ -3
-_
2
I
-1 Eog Cd
_± 0
1
Fig. 4. Apparent transport number of sulphate cs. log Cd plots of the data obtained in the AEAPSmoditied membrane system with cupric sulphate solution.
the apparent transport number of sulphate c s . log C d plots of the data obtained in the AEAPS-modified membrane system with a cupric sulphate solution. In this case, a 0.01M solution of cupric sulphate was located in the o compartment and another Ca M solution of the same kind of salt was in the d compartment. When the concentration of cupric sulphate is low (the left side of the Fig. 4), the protonation of amino groups precedes the formation of the complex Cu(II) ion with N-2aminoethyl-3-aminopropyl groups on the membrane surface, and this gives the membrane anion-selective properties. When the concentration of cupric sulphate is high (over 0.1M), the Cu(II) ion forms complex with N-2-aminoethyl-3aminopropyl groups on the membrane surface. Moreover, the modified membrane shows (the right side of the Fig. 4) cation-selective properties in spite of the protonated amino groups on the membrane surface. It means that the Cu(ll)ion not only forms complex with N-2-aminoethyl-3-aminopropyl groups but moves on the membrane surface. REFERENCES l 2
J. Sagiv, J. Am. ('/win. £'o~., 102 (1980) 92. T . H . Chiang. A. N a k a m u r a . K. Nishiza~sa and I:. Toda, ,\'IPPO,\' K,4U,4K[" K.41£'HI. l / (1987) 2O52.