A Comparison of Perfluorinated Carboxylate and Sulfonate Ion Exchange Polymers: I . Diffusion and Water Sorption

Yeager, H. L.; Twardowski, Zbigniew; Clarke, Loyal

doi:10.1149/1.2123820

Cited by 59 publications

(47 citation statements)

References 9 publications

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“…At a low value of the pH the carboxylic membrane may be protonated, resulting in a very high (electrical) resistance and loss of the selectivity. According to Yeager (1982a), protonation of the carboxylic layer starts at a pH value of about 4 and has a major e!ect on the ability of Na> to di!use through the polymer matrix. Moreover, in industry, acid is even added to the anode compartment which could result in a pH value of less than 2.…”

Section: Determination Of Maxwell}stefan Di4usivities For the Chloralmentioning

confidence: 99%

Application of the Maxwell–Stefan theory to the transport in ion-selective membranes used in the chloralkali electrolysis process

Stegen

Veen

Weerdenburg³

et al. 1999

Chemical Engineering Science

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The results of a fundamental mass transport model based on the Maxwell}Stefan approach are compared to experimental data obtained by Akzo-Nobel for a Dupont Na"on ion-selective membrane as used in chloralkali electrolysis processes. The main problem in the application of the Maxwell Stefan based mass transfer model to the chloralkali electrolysis process is a lack of available di!usivities for the membrane. Estimation of these di!usivities in the membrane based on a method presented by Wesselingh et al. (1995. Chem. Engng J., 57, 75}89) gave unrealistic high membrane potential drops. Therefore, another method was followed. First, a sensitivity analysis was carried out which resulted in a reduced set consisting of the dominating Maxwell}Stefan di!usivities. First estimates of these remaining di!usivities were determined for single layer sulfonic and a carboxylic membranes. With a slight adjustment of the values of the di!usivities obtained for the separate sulfonic and carboxylic layers, the performance parameters of the DuPont Na"on membrane could be predicted well for a reference experiment. These di!usivities also proved to be suitable for other anolyte strengths. However, for other catholyte strengths and current densities these di!usivities (even after a correction for the water uptake according to the method of Wesselingh et al. (1995. Chem. Engng. 5., 57, 75}89)) did not result in a good agreement between the simulated and experimentally observed performance parameters. Only after a correction of the di!usivities the simulations yielded approximately the same performance parameters as experimentally observed. From this it can be concluded that although a fundamental model is used in order to describe the mass transfer in a membrane, a single set of di!usivities is not su$cient in order to obtain the experimentally observed performance parameters at di!erent process conditions. At this moment there is not enough knowledge on the exact phenomena taking place in the membrane in order to predict the necessary corrections of the di!usivities a priori. As long as there are no theoretically founded and reliable relations available to predict the Maxwell}Stefan di!usivities in a membrane (or accurate experimental data for these di!usivities) only a semi-empirical method as used in this study can serve as a basis for a further progress in the development of an existing (in this case DuPont Na"on) membrane.

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Section: Determination Of Maxwell}stefan Di4usivities For the Chloralmentioning

confidence: 99%

Application of the Maxwell–Stefan theory to the transport in ion-selective membranes used in the chloralkali electrolysis process

Stegen

Veen

Weerdenburg³

et al. 1999

Chemical Engineering Science

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“…The general logistic function is shown in Eq. (9) in which A and B are the lower and upper asymptote values respectively, k defines the slope of the curve, and x 0 is the midpoint of the curve.…”

Section: Model Approach and Assumptionsmentioning

confidence: 99%

“…For a proper bilayer model, reliable data for diffusivities of each membrane layer are required. However, in the literature, there are not enough data on diffusivities of all sodium, hydroxide, and chloride ions in the sulfonate and carboxylate layers [9,10,22]. The sodium self-diffusion coefficient in both sulfonate and carboxylate membranes has been reported in a sodium chloride and sodium hydroxide solution by Ames [22].…”

Section: Model Approach and Assumptionsmentioning

confidence: 99%

“…The sodium self-diffusion coefficient in both sulfonate and carboxylate membranes has been reported in a sodium chloride and sodium hydroxide solution by Ames [22]. He reported the sodium self-diffusion coefficient to be one order of magnitude higher in the sulfonate layer in both sodium chloride and sodium hydroxide solutions [8,9]. On the other hand, Yeager et al and Twardowski et al have measured a slightly higher sodium diffusion coefficient in the sulfonate compared to the carboxylate membranes in sodium chloride solution [8,22].…”

Section: Model Approach and Assumptionsmentioning

confidence: 99%

“…In spite of a number of literature studies on the structure of cation-exchange membranes [2][3][4][5][6][7], there have been few studies looking into the structure and performance of bilayer membranes individually [8][9][10]. Also, virtually, no data exist in the literature that compares the performance of mono-and bilayer cation-selective membranes especially at high current densities.…”

Section: Introductionmentioning

confidence: 99%

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Multicomponent ion transport in a mono- and bilayer cation-exchange membrane at high current density

et al. 2016

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This work describes a model for bilayer cationexchange membranes used in the chlor-alkali process. The ion transport inside the membrane is modeled with the Nernst-Planck equation. A logistic function is used at the boundary between the two layers of the bilayer membrane to describe the change in the properties of each membrane layer. The local convective velocity is calculated inside the membrane using the Schlögl equation and the equation of continuity. The model calculates the ion concentration profiles inside the membrane layers. Modeling results of mono-and bilayer membranes are compared. The changes in membrane voltage drop and sodium selectivity are predicted. The concentration profile of sodium ions in the bilayer membrane is significantly different from the monolayer membrane. Without the applied current, a linear change in the sodium concentration is observed in the monolayer membrane and in each layer of the bilayer membrane. With an increase in current density, the stronger electromotive force in the carboxylate layer causes a decrease in the sodium concentration in the sulfonate layer, down to the fixed ionic group concentration. This significant decrease of sodium ion concentration in the sulfonate layer results in low concentrations of counter ions and as a consequence a higher permselectivity of the bilayer membrane is obtained when compared to the single-layer membrane. As a drawback, the resistance in the bilayer membrane increases.

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Solute permeation through perfluorocarboxylate membranes

Koyama

Satoh

Iijima

1987

Angew. Makromol. Chem.

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The sorption and permeability of tetraalkylammonium chlorides and alkali chlorides in perfluorocarboxylate membranes were determined. The water content and density of the membranes were found to change with treatment in boiling water and with different tetraalkylammonium cations as counterions for the wboxylate fiied charge. This is attributed to a change in the structure of the membrane matrices. DSC measurements suggested the existence of three distinct phases in the membranes, i.e. a free water phase, a bound water phase, and nonfreezable water. The nonfreezable water was assumed to be in the fluorocarbon phase. The permeability sequence of the tetraalkylammonium chlorides was found to be TEACl > TMACl > TBACl. To interpret the results, a parallel permeation model was proposed. ZUSAMMENFASSUNG:Es wurde die Sorption und Permeabilitilt von Tetraalkylammonium-und Alkalichloriden durch Perfluorwboxylatmembranen bestimmt. Der Wassergehalt und die Dichte der Membranen ilnderten sich durch die Behandlung mit siedendem Wasser und mit verschiedenen Tetraalkylammoniumkationen als Gegenionen fiir die fiierten Carboxylatladungen. Das wird auf eine Vertinderung der Struktur der Membranen zuriickgefiihrt. DSC Messungen weisen auf das Vorhandensein von drei unterschiedlichen Phasen des Wassers in den Membranen hin und zwar das freie Wasser, gebundenes Wasser und nicht gefrierbares Wasser. Das nicht gefrierbare Wasser wird in der Fluorkohlenstoffphase angenommen. Die Reihenfolge der Permeabilitilt der Tetraalkylammoniumchloride ergab sich zu TEACl > TMACl > TBAC1. Zur E r k l h n g der Ergebnisse wurde ein Parallel-Permeation-Modell vorgeschlagen.

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A Comparison of Perfluorinated Carboxylate and Sulfonate Ion Exchange Polymers: I . Diffusion and Water Sorption

Cited by 59 publications

References 9 publications

Application of the Maxwell–Stefan theory to the transport in ion-selective membranes used in the chloralkali electrolysis process

Application of the Maxwell–Stefan theory to the transport in ion-selective membranes used in the chloralkali electrolysis process

Multicomponent ion transport in a mono- and bilayer cation-exchange membrane at high current density

Solute permeation through perfluorocarboxylate membranes

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