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Equilibrium and electrotransport properties of the perfluorinated membranes of Nafion and MF-4SC types
Desalination 200 (2006) 163–165
Equilibrium and electrotransport properties of the perfluorinated membranes of Nafion and MF-4SC types Ninel Berezina*, Aleksey Dyomin, Olga Dyomina, Victor Zabolotsky Department of Physical Chemistry, Kuban State University, Stavropolskaya str., 149, 350040, Krasnodar, Russia email: [email protected] Received 19 October 2005; accepted 6 March 2006
1. Introduction Recently the perfluorinated ionomer membranes are the objects of intensive investigations because of their high performance in electromembrane technology, fuel cells and sensor technics. The aim of the study is to research and compare the physico-chemical properties of home-made perfluorinated sulfocationic membranes MF-4SC (Russia) and Nafion type (USA) in the same conditions of pretreatment and experimental techniques. 2. Experimental Electroconductivity (k), diffusion (P) and electrooosmotical (tw) permeability and the main equilibrium characteristics of the membranes: ion-exchange capacity (Q), water content (W), sample thickness (l), were measured in isothermal conditions by methods described in [1,2]. As objects of research were the families of MF4SC and Nafion of trade marks. The physicochemical properties of samples investigated are given in Table 1. We have used also the series of experiment samples MF-4SC, which were *Corresponding author.
researched in our works earlier [1,3]. So, the properties of 11 samples of the membranes have been compared.
3. Results and discussion The obtained concentration plots of electroconductivity (a) and electroosmotical coefficient (water transport numbers) (b) are shown in Fig. 1. Dependencies of diffusion permeability coefficients on the NaCl concentration (a) and hydrate capacity (b) are demonstrated in Fig. 2. All data confirmed the key role of water content. It is found that the dependencies electroconductivity, diffusion permeability and water transport numbers on the fixed external concentration have threshold character, which is demonstrated in Fig. 2a. The critical value of hydrate capacity is equal about 10 mol H2O/mol SO3– . Beginning with one we observe the strong change of electroconductivity and diffusion permeability both for MF-4SC and Nafion membranes. It is interesting to note that the reinforcing fibres in Nafion-425 influence on transport properties more essentially than in the case membranes MF-4SC-101 because of differences of fibres porosity (Table 1) and production technology.
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.03.282
164
N. Berezina et al. / Desalination 200 (2006) 163–165
Table 1 Physico-chemical characteristics of the perfluorinated membranes of the commercial type Membranes
L (mm)
Reinforcing fibres
EW
Q (mg–eq/gsw)
Wsw (%) 0.1 M NaCl
n, mol H2O/mol SO3– 0.1 M NaCl
MF-4SC MF-4SC-101 Nafion-115 Nafion-117 Nafion-425
0.21 0.32 0.17 0.23 0.37
– Ftorlon – – Gora-tex
1200 1200 1100 1100 1200
0.72 0.70 0.80 0.76 0.68
9.7 12.5 12.1 15.5 15.8
7.7 9.9 8.4 11.3 12.9
12 6.5
11 10
5.5 tw, mol H2O/F
k × 103, Sm/sm
9 8 7 6 5 4
4.5 3.5 2.5
3 2 0.00
0.02
(a)
0.04 0.06 C, mol/L
0.08
1.5 0.0
0.10
0.5
1.0
(b)
1.5 2.0 C, mol/L
2.5
3.0
Fig. 1. The concentration dependencies of specific conductivity (a) and water transport number (b).
6 5 P × 108, sm2 s–1
P × 108, sm2 s–1
20 15 10 5 0 0.0
(a)
4 3 2 1 0
0.2
0.4
0.6 C, mol/L
0.8
1.0
0
(b)
2
4
6
8
10
12
n, mol H2O/mol SO3–
Fig. 2. The dependencies of diffusion permeability vs. the NaCl concentration (a) and hydrate capacity (b): membranes designations are the same as in Fig. 1.
N. Berezina et al. / Desalination 200 (2006) 163–165
4. Conclusions As a result of our experiment we have arrived at the following conclusions: the water content and its state in polymer structure have a decisive influence on the character of the concentration dependencies of the membranes transport properties. References [1]
N. Berezina, N. Gnusin, O. Dyomina and S. Timofeyev, Water electrotransport in membrane
[2]
[3]
165
systems. Experiment and model description, J. Membr. Sci., 86 (1994) 207–229. N.P. Gnusin, N.P. Berezina, O.A. Dyomina and N.A. Kononenko, Physicochemical principles of testing ion-exchange membranes, Elektrohimiya, 32 (1996) 173–182. O.P. Ivina, M.Ya. Shokhman, N.P. Berezina, et al., Influence of preparation conditions of MF4SC membranes on their electroconductivity and diffusion properties, Zhurnal Fizicheskoy Khimii, 66 (1992) 2758–2762.
Equilibrium and electrotransport properties of the perfluorinated membranes of Nafion and MF-4SC types Ninel Berezina*, Aleksey Dyomin, Olga Dyomina, Victor Zabolotsky Department of Physical Chemistry, Kuban State University, Stavropolskaya str., 149, 350040, Krasnodar, Russia email: [email protected] Received 19 October 2005; accepted 6 March 2006
1. Introduction Recently the perfluorinated ionomer membranes are the objects of intensive investigations because of their high performance in electromembrane technology, fuel cells and sensor technics. The aim of the study is to research and compare the physico-chemical properties of home-made perfluorinated sulfocationic membranes MF-4SC (Russia) and Nafion type (USA) in the same conditions of pretreatment and experimental techniques. 2. Experimental Electroconductivity (k), diffusion (P) and electrooosmotical (tw) permeability and the main equilibrium characteristics of the membranes: ion-exchange capacity (Q), water content (W), sample thickness (l), were measured in isothermal conditions by methods described in [1,2]. As objects of research were the families of MF4SC and Nafion of trade marks. The physicochemical properties of samples investigated are given in Table 1. We have used also the series of experiment samples MF-4SC, which were *Corresponding author.
researched in our works earlier [1,3]. So, the properties of 11 samples of the membranes have been compared.
3. Results and discussion The obtained concentration plots of electroconductivity (a) and electroosmotical coefficient (water transport numbers) (b) are shown in Fig. 1. Dependencies of diffusion permeability coefficients on the NaCl concentration (a) and hydrate capacity (b) are demonstrated in Fig. 2. All data confirmed the key role of water content. It is found that the dependencies electroconductivity, diffusion permeability and water transport numbers on the fixed external concentration have threshold character, which is demonstrated in Fig. 2a. The critical value of hydrate capacity is equal about 10 mol H2O/mol SO3– . Beginning with one we observe the strong change of electroconductivity and diffusion permeability both for MF-4SC and Nafion membranes. It is interesting to note that the reinforcing fibres in Nafion-425 influence on transport properties more essentially than in the case membranes MF-4SC-101 because of differences of fibres porosity (Table 1) and production technology.
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.03.282
164
N. Berezina et al. / Desalination 200 (2006) 163–165
Table 1 Physico-chemical characteristics of the perfluorinated membranes of the commercial type Membranes
L (mm)
Reinforcing fibres
EW
Q (mg–eq/gsw)
Wsw (%) 0.1 M NaCl
n, mol H2O/mol SO3– 0.1 M NaCl
MF-4SC MF-4SC-101 Nafion-115 Nafion-117 Nafion-425
0.21 0.32 0.17 0.23 0.37
– Ftorlon – – Gora-tex
1200 1200 1100 1100 1200
0.72 0.70 0.80 0.76 0.68
9.7 12.5 12.1 15.5 15.8
7.7 9.9 8.4 11.3 12.9
12 6.5
11 10
5.5 tw, mol H2O/F
k × 103, Sm/sm
9 8 7 6 5 4
4.5 3.5 2.5
3 2 0.00
0.02
(a)
0.04 0.06 C, mol/L
0.08
1.5 0.0
0.10
0.5
1.0
(b)
1.5 2.0 C, mol/L
2.5
3.0
Fig. 1. The concentration dependencies of specific conductivity (a) and water transport number (b).
6 5 P × 108, sm2 s–1
P × 108, sm2 s–1
20 15 10 5 0 0.0
(a)
4 3 2 1 0
0.2
0.4
0.6 C, mol/L
0.8
1.0
0
(b)
2
4
6
8
10
12
n, mol H2O/mol SO3–
Fig. 2. The dependencies of diffusion permeability vs. the NaCl concentration (a) and hydrate capacity (b): membranes designations are the same as in Fig. 1.
N. Berezina et al. / Desalination 200 (2006) 163–165
4. Conclusions As a result of our experiment we have arrived at the following conclusions: the water content and its state in polymer structure have a decisive influence on the character of the concentration dependencies of the membranes transport properties. References [1]
N. Berezina, N. Gnusin, O. Dyomina and S. Timofeyev, Water electrotransport in membrane
[2]
[3]
165
systems. Experiment and model description, J. Membr. Sci., 86 (1994) 207–229. N.P. Gnusin, N.P. Berezina, O.A. Dyomina and N.A. Kononenko, Physicochemical principles of testing ion-exchange membranes, Elektrohimiya, 32 (1996) 173–182. O.P. Ivina, M.Ya. Shokhman, N.P. Berezina, et al., Influence of preparation conditions of MF4SC membranes on their electroconductivity and diffusion properties, Zhurnal Fizicheskoy Khimii, 66 (1992) 2758–2762.