Transport Properties Of Ion-exchange Membranes Research Articles

Study of the Thermochemical Effect on the Transport and Structural Characteristics of Heterogeneous Ion-Exchange Membranes by Combining the Cell Model and the Fine-Porous Membrane Model.

For the first time, based on the joint application of the fine-porous and cell models, a theoretical analysis of the changing transport and structural characteristics of heterogeneous polymeric ion-exchange membranes (IEMs) MK-40, MA-40, and MA-41 after exposure to elevated temperatures in water and aggressive media (H2SO4 and NaOH solutions), as well as after long-term processing in electrodialyzers of various types, was carried out. The studied membranes are composites of ion-exchange polymers with polyethylene and nylon reinforcing mesh. The external influences provoke the aging of IEMs and the deterioration of their characteristics. The transport properties of IEMs are quantitatively described using five physicochemical parameters: counterion diffusion and equilibrium distribution coefficients in the membrane, characteristic exchange capacity, which depends on the microporosity of ion-exchanger particles, and macroscopic porosity at a known exchange capacity of IEMs. Calculations of the physicochemical parameters of the membranes were performed according to a specially developed fitting technique using the experimental concentration dependences of integral diffusion permeability and specific electrical conductivity, and their model analogs. This made it possible to identify and evaluate changes in the membrane micro- and macrostructure and examine the process of artificial aging of the IEM polymer material due to the abovementioned external impacts.

Effect of Lactose on the Transport Properties of Ion-Exchange Membranes

Effect of Lactose on the Transport Properties of Ion-Exchange Membranes

The Effect of Lactose on the Transport Properties of Ion-Exchange Membranes

The influence of lactose on the basic transport characteristics of ion exchange membranes, including cation-exchange membranes modified by polyaniline, has been studied. A positive effect on biofouling by Bacillus sp. or Shewanella oneidensis MR-1 cell cultures of modified MK-40 and Ralex CMHPES membranes has been found. That is mainly due to the different area of the conductive surface of these membranes. It has been revealed that the presence of lactose in a solution leads to a decrease in the conductivity of all studied membranes. However, the most significant effect is manifested for MK-40 membrane modified by polyaniline: its electrical conductivity is reduced by 15–25%. The diffusion permeability of the anion-exchange and initial cation-exchange membranes is poorly dependent on the presence of lactose in the solution. However, its decrease is observed by 2–2.5 times in the case of cation-exchange membranes modified by polyaniline. A significant effect of lactose on the current-voltage characteristics of the anion-exchange membranes has been found. This fact indicates significant adsorption of lactose on membrane surface in an external electric field. It is shown that ion-exchange membranes remain quite effective for electrodialysis of hydrochloric serum solutions, but their use is more effective at under limiting current modes.

Modeling the Conductivity and Diffusion Permeability of a Track-Etched Membrane Taking into Account a Loose Layer.

The microheterogeneous model makes it possible to describe the main transport properties of ion-exchange membranes using a single set of input parameters. This paper describes an adaptation of the microheterogeneous model for describing the electrical conductivity and diffusion permeability of a track-etched membrane (TEM). Usually, the transport parameters of TEMs are evaluated assuming that ion transfer occurs through the solution filling the membrane pores, which are cylindrical and oriented normally to the membrane surface. The version of the microheterogeneous model developed in this paper takes into account the presence of a loose layer, which forms as an intermediate layer between the pore solution and the membrane bulk material during track etching. It is assumed that this layer can be considered as a "gel phase" in the framework of the microheterogeneous model due to the fixed hydroxyl and carboxyl groups, which imparts ion exchange properties to the loose layer. The qualitative and quantitative agreement between the calculated and experimental concentration dependencies of the conductivity and diffusion permeability is discussed. The role of the model input parameters is described in relation to the structural features of the membrane. In particular, the inclination of the pores relative to the surface and their narrowing in the middle part of the membrane can be important for their properties.

Selectivity of Transport Processes in Ion-Exchange Membranes: Relationship with the Structure and Methods for Its Improvement.

Nowadays, ion-exchange membranes have numerous applications in water desalination, electrolysis, chemistry, food, health, energy, environment and other fields. All of these applications require high selectivity of ion transfer, i.e., high membrane permselectivity. The transport properties of ion-exchange membranes are determined by their structure, composition and preparation method. For various applications, the selectivity of transfer processes can be characterized by different parameters, for example, by the transport number of counterions (permselectivity in electrodialysis) or by the ratio of ionic conductivity to the permeability of some gases (crossover in fuel cells). However, in most cases there is a correlation: the higher the flux density of the target component through the membrane, the lower the selectivity of the process. This correlation has two aspects: first, it follows from the membrane material properties, often expressed as the trade-off between membrane permeability and permselectivity; and, second, it is due to the concentration polarization phenomenon, which increases with an increase in the applied driving force. In this review, both aspects are considered. Recent research and progress in the membrane selectivity improvement, mainly including a number of approaches as crosslinking, nanoparticle doping, surface modification, and the use of special synthetic methods (e.g., synthesis of grafted membranes or membranes with a fairly rigid three-dimensional matrix) are summarized. These approaches are promising for the ion-exchange membranes synthesis for electrodialysis, alternative energy, and the valuable component extraction from natural or waste-water. Perspectives on future development in this research field are also discussed.

Dependence of the Transport Properties of Perfluorinated Sulfonated Cation-Exchange Membranes on Ion-Exchange Capacity

The transport properties of ion-exchange membranes depend on many factors, primarily, on ion-exchange capacity and chemical composition. Therefore, the correlation of transport properties with a single particular parameter is generally not quite strict. In this study, the dependence of transport properties of several perfluorinated sulfonated cation-exchange membranes that differ in side chain length and fraction of fragments containing ether groups on ion-exchange capacity is analyzed. It is shown that, with a decrease in the ion-exchange capacity from 1.35 to 0.66 mg-equiv/g, the proton conductivity of membranes contacting water and their diffusion permeability with respect to a 0.1 M HCl solution decrease by two orders of magnitude. A decrease in relative humidity leads to the most significant decrease in the conductivity of membranes with a low ion-exchange capacity. Thus, at a relative humidity of 32%, the conductivity of the studied membranes decreases more than 600-fold with a decrease in ion-exchange capacity. In general, the oxygen permeability of membranes is characterized by a similar dependence. However, in this set of membranes, it varies as little as threefold.

Modified Microheterogeneous Model for Describing Electrical Conductivity of Membranes in Dilute Electrolyte Solutions

Many transport properties of ion-exchange membranes can be described in terms of the microheterogeneous model using a single set of parameters. However, the model is applicable in a limited concentration range of electrolyte solutions. In this paper a new modification of this model is proposed, taking into account the contribution of the electrical double layer (EDL) at the internal boundaries of the gel phase and the intergel solution of the membrane to describe the electrical conductivity of membranes in dilute electrolyte solutions. The model suggests that the EDL thickness in the internal solution phase increases with dilution of the external solution. Since EDL is more conductive than the electroneutral part of the solution, it is possible to describe the concentration dependence of the electrical conductivity of membrane more precisely as compared with the basic version of the microheterogeneous model. Comparison of the concentration dependences of the electrical conductivity of membranes shows a good agreement between the experimental and calculated data.

Influence of preparation procedure and ferric oxide nanoparticles addition on transport properties of homogeneous cation-exchange SPPO/SPVC membrane

Homogeneous cation-exchange membranes were prepared through evaporation and phase inversion methods using sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) and sulfonated polyvinylchloride as binders. The effect of polymers blend’s ratio and preparation method on structure and electrochemical properties of the prepared membranes were evaluated. The microstructures of the membranes were investigated by scanning electron microscopy (SEM) and the sulfonation of polyvinylchloride was confirmed by elemental analyses. Moreover, the membranes performance was evaluated by ion-exchange capacity (IEC), fixed ion concentration, membrane potential, transport number, permselectivity, areal resistance, ionic permeability, flux of ions, current efficiency, membrane oxidative stability, mechanical properties and water content tests. The results indicated that IEC and water content were affected by the SPPO content and microstructures of the membranes. The results showed increased efficiency and suitable electrochemical properties for membranes prepared by the evaporation method in comparison with others. Also, \(\hbox {Fe}_{2}\hbox {O}_{3}\) nanoparticles were synthesized at room temperature by a simple sonochemical reaction between ferric chloride and NaOH. The results revealed that the addition of different amounts of \(\hbox {Fe}_{2}\hbox {O}_{3}\) nanoparticles to the polymeric matrix could affect the hydrophilicity and transport properties of ion-exchange membranes.

The possibility of changing the transport properties of ion-exchange membranes by their treatment

A very important challenge in the membrane science is to improve the transport properties of membranes by means of various treatment methods. The review, using the example of homogeneous perfluorinated membranes, discusses the causes of changes in these properties by heat treatment at different water activities, mechanical treatment, and introduction of nanoparticles of various materials into their matrix.

Influence of aqueous–organic solutions containing aprotic solvent on equilibrium and transport properties of ion–exchange membranes

Equilibrium and transport properties of ion-exchange electrodialytic membranes before and after their processing in model solution containing dimethylacetamide were investigated in LiCl solutions. Values of the membranes transport structural parameters reflecting structural and kinetic characteristics of the two-phase system were derived on the basis of electroconductivity and diffusion permeability concentration dependences of investigated membranes. Aprotic solvent influence on the properties of heterogeneous membranes and their transport structural parameters ware discovered.

Model verification of limiting concentration by electrodialysis of an electrolyte solution

The concentration of LiCl in brine and brine volume are obtained as functions of current density by the method of limiting concentration by electrodialysis. These relationships are used for model calculations of current efficiency, the diffusion, osmotic, and electroosmotic permeability of an MK-40/MA-40 membrane pair, and also salt hydration numbers. These theoretical values of water transport numbers and LiCl hydration numbers are compared with corresponding experimental and literature data. It is shown that the model adequately describes the phenomena of the mass electrotransport occurring in electrodialyzers with noncirculating concentration compartments, and it can be successfully applied in calculating the technological parameters of the process, finding the transport properties of ion-exchange membranes, and determining salt hydration numbers in aqueous electrolyte solutions.

Effects of transport properties of ion-exchange membranes on desalination of 1,3-propanediol fermentation broth by electrodialysis

The electrodialysis (ED) method has been employed successfully to remove organic salts from fermentation broth. The efficiency of ED is strongly affected by the transport properties of ions and solutes through ion-exchange membranes (IEMs), that is, the conductivity of the IEM and the diffusion coefficient of neutral solutes through the IEM. Therefore, it is very important to select IEMs being suitable for ED desalination of fermentation broth based on the transport properties of IEMs. The conductivities of eight kinds of commercial IEMs and the diffusion coefficients of neutral solutes through the IEMs were measured, and ED experiments for the desalination of simulated 1,3-propanediol fermentation broth were carried out by using a combination of the eight IEMs. By comparing the efficiency of the ED process, the optimum IEMs were determined and the influences of transport properties of IEMs were discussed.

Micellar-enhanced electrodialysis: Influence of surfactants on the transport properties of ion-exchange membranes

Thin layers of ionic surfactants were formed on the surfaces of ion-exchange membranes by adsorption with electrostatic interactions and were conformed by FTIR spectra. The effect of the adsorption on the transmission characteristics were investigated by membrane resistance and permselectivity studies, and it was found that adsorption of cationic surfactant onto the cation-exchange membrane and anionic surfactant onto the anion-exchange membrane associated with the increase in membrane resistance while decrease in membrane permselectivity, which became limiting beyond the critical micelle concentration of respective surfactant. Based on the studies schematic model for the orientations of surfactant molecules on the membranes surfaces under the electrodialytic conditions was presented. Improvement in the electrodialysis (ED) process efficiencies was observed due to the adsorption of the ion-exchange membranes surfaces because of the reduction in the concentration gradient between dilute and concentrated compartments of the ED unit, and thus back diffusion. This phenomenon is also schematically presented by the concentration profiles across the ion-exchange membranes under the electrical gradient in the polarized conditions. Based on the experimental results so called micellar-enhanced electrodialysis has been proposed for the efficient electrolyte separation up to very low concentration (with high purity) with reduced energy consumption, concentration polarization and improved limiting current density.

A simplified procedure for ion-exchange membrane characterisation

A new procedure for the characterisation of the transport properties of ion-exchange membranes (IEM) is proposed. Only three characteristics have to be measured: the electrical conductivity, the diffusion permeability coefficient and the apparent transport number. To complete the set of parameters, two complementary characteristics, the true counter-ion transport number and the water transport number, are calculated from the Scatchard equation and from a novel equation deduced earlier. The possibilities to reduce the number of initial measurements are discussed in three cases.

The effect of conducting spacers on transport properties of ion-exchange membranes in electrodriven separation

A conventional non-conducting spacer (interpolymer of polyethylene styrene-divinylbenzene copolymer) was transformed into an ion-conducting spacer by chemical modifications. Electrochemical characterization of cation-and anion-exchange membranes when it was alone or kept in between the non-, cation- or anion-conducting spacers was carried out by recording membrane potential and current-voltage curves in contact with NaCl solution of 220 ppm concentration at different flow rate of the solution. Transport parameters such as the counter-ion transport number, ionic permeability, membrane resistance and permselectivity were estimated for different experimental systems. Introduction of cation-conducting spacer near cation-exchange membrane and anion-conducting spacer near anion-exchange membrane led to a dramatic increase in counter-ion transport number and limiting current density along with the reduction in membrane resistance and thickness of diffusion boundary layer. On the basis of these studies, the position of conducting spacers (CS) in electrodialysis (ED) stack were optimized and packed. The performance of this ED stack has been tested with non-conducting and cation-conducting spacers in electrolytic solution of NaCl, NiCl 2 and CuCl 2 having concentration 500–1000ppm. The presence of conducting spacers not only suppress the concentration polarization but out put of the unit and its current efficiency also increases by about two times.

Equilibrium and transport properties of ion-exchange membranes

Specific properties (ion-exchange capacity, water content, pore volume fraction) and transport properties (counterion transport number and electrical conductivity) have been measured in four commercial cation-exchange membranes loaded with a variety of cations of different nature and charge. Not surprisingly, equivalent conductances are lower than in free solution and transport numbers decrease with valency of the counterion. This behavior is explained by taking into account a “tortuosity factor”, due to a lengthening of the pores across the membrane, except for a membrane with a lower water content and for ions of higher charge, in which electrostatic interactions between mobile and fixed charges seem to be a predominant effect.

Effect of membrane matrix on the transport of potassium ions

Journal of Applied Polymer ScienceVolume 18, Issue 9 p. 2855-2859 NoteFree Access Effect of membrane matrix on the transport of potassium ions Richard A. Wallace, Richard A. Wallace Stanford University, Stanford, California 94305 Oregon Graduate Center and University of Oregon Medical School Portland, Oregon 97201Search for more papers by this author Richard A. Wallace, Richard A. Wallace Stanford University, Stanford, California 94305 Oregon Graduate Center and University of Oregon Medical School Portland, Oregon 97201Search for more papers by this author First published: September 1974 https://doi.org/10.1002/app.1974.070180926Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL References 1 R. A. Wallace and J. P. Ampaya, Desalination J., 14, 121 (1974). 2 H. P. Gregor, Membrane Phenomena, Research and Development Progress Report No. 193, Office of Saline Water, Washington, D. C., 1966, p. 27. 3 F. Helfferich, Ion Exchange, McGraw-Hill, 1962, p. 583. 4 L. Michaelis, in Physical Methods of Organic Chemistry, Vol. 2, A. Weissberger, Ed., Interscience, New York, 1946 p. 1096. 5 H. P. Gregor, Membrane Phenomena, Research and Development Progress Report No. 193, Office of Saline Water, Washington, D.C., 1966, p. 73. 6 J. H. B. George, R. A. Horne, and C. R. Schlaikjer, Investigation of the Transport Properties of Ion-Exchange Membranes, Final Report, Office of Saline Water, Washington, D.C., 1967. 7 W. J. Moore, Physical Chemistry, 3rd ed., Prentice-Hall, Englewood Cliffs, New Jersey, 1963, p. 337. 8 A. O. Jakubovic, G. J. Hills, and J. A. Kitchener, Trans. Faraday Soc., 55, 1570 (1959). Citing Literature Volume18, Issue9September 1974Pages 2855-2859 ReferencesRelatedInformation

Correlation between ion exchange membrane conductivity and the frequency effect

Journal of Applied Polymer ScienceVolume 17, Issue 1 p. 309-313 NoteFree Access Correlation between ion exchange membrane conductivity and the frequency effect Richard A. Wallace, Richard A. Wallace Department of Materials Science and Engineering, Stanford University, Stanford, California 94305Search for more papers by this author Richard A. Wallace, Richard A. Wallace Department of Materials Science and Engineering, Stanford University, Stanford, California 94305Search for more papers by this author First published: January 1973 https://doi.org/10.1002/app.1973.070170125Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References 1 F. Helfferich, Ion Exchange, McGraw-Hill, 1962. 2 F. deKorosy, Nature, 191, 1363 (1961). 3 K. Arulanandan, Dissertation, University of California, Berkeley, 1966 4 S. B. Sachs and K. S. Spiegler, J. Phys. Chem., 68, 1214 (1964). 5 K. S. Spiegler, Study of Membrane-Solution Interfaces by Electrochemical Methods, Office of Saline Water, Report No. 652, U. S. Dept. of the Interior, Washington, D. C., 1969. 6 J. H. B. George, R. A. Horne, and C. R. Schlaikjer, An Investigation of Transport Properties of Ion-Exchange Membranes, Office of Saline Water Report No. 321, U. S. Dept. of the Interior, Washington, D. C., 1967. 7 J. R. Macdonald, J. Chem. Phys., 54, 2026 (1971). 8 J. H. B. George and C. R. Schlaikjer, An Investigation of Transport Properties of Ion-Exchange Membranes, Office of Saline Water Report No. 372, U. S. Dept. of the Interior, Washington, D. C., 1968. 9 T. Teorell, Z. Elektrochem. 55, 460 (1951). Citing Literature Volume17, Issue1January 1973Pages 309-313 ReferencesRelatedInformation

Transport properties of ion-exchange membranes in the presence of surface active agents

Transport properties of ion-exchange membranes in the presence of various surface-active agents were observed. Measurements were carried out by the following two methods: (1) electrodialysis using a cation exchange membrane which has been adsorbed or ion exchanged with hexadecyl pyridinium chloride; (2) electrodialysis of a mixed salt solution containing surface-active agents using anion or cation exchange membranes. The transport properties measured in this report were: the relative transport number of two ionic species with the same sign ( P M 2 M 1 ), the current efficiency, the voltage drop by electric resistance of the membrane during the electrodialysis, and the current-voltage curve. P M 2 M 1 of cation exchange membranes was changed remarkably by adsorption of or ion exchange with the cationic surface-active agent above a certain concentration, but was not changed by adsorption of a nonionic or anionic surface-active agent. Similarly, P M 2 M 1 of anion exchange membrane changed remarkably by adsorption of or ion exchange with an anionic surface-active agent. The cation exchange membrane in the presence of cationic surface-active agents and the anion exchange membrane in the presence of anionic surface-active agents were preferentially permeable to monovalent ions over multivalent ions. The current-voltage curves were characteristic of a bipolar ion-exchange membrane. These membranes were preferentially permeable to monovalent ions because the electrostatic repulsion force between the multivalent ions and the surface charge of the membrane is larger than that between the monovalent ion and the surface charge of the membrane. The current efficiency of cation exchange membrane decreased slightly with an increase in the amount of dodecyl pyridinium chloride adsorbed or ion exchanged. However, the current efficiency decreased or increased depending on the species of surface-active agent and ion-exchange membrane. The voltage drop due to the electrical resistance of the cation exchange membrane increased as the electrodialysis proceeded and also as the concentration of cationic surface-active agent was increased.