journal of MEMBRANE SCIENCE ELSEVIER Journal of Membrane Science 136 (1997) 35-39 An early history of electrodialysis with permselective membranes V.A. S h a p o s h n i k a, K. K e s o r e b'* aDepartment of Analytical Chemistry, Faculty of Chemistry, Voronejh State University, 1, University Place, 394693 Voronejh, Russian Federation blnstitute of Technical Chemistry and Macro-molecular Chemistry, Martin-Luther-University Halle-Wittenberg, 06108 Halle~S, Germany Received 12May 1997; accepted 10 June 1997 Abstract This paper outlines the main stages in the history of electrodialysis, from the discovery of the method in 1890 to the development of the fundamental principles of matter-separation and chemical conversions. The evolution of electrodialysis is closely bonded to the birth of the concept considering the presence of fixed charges and mobile counter-ions in ion exchange membranes. The main and basic role of the idea about alternating anion exchange membranes and cation exchange membranes in multi-compartment apparatus (1940) has been described here. Attention has been devoted as well to the synthesis of anion-permeable membranes from anion exchange resins and cation-permeable membranes from cation exchange resins (1950). An analysis of the results of the early applications of electrodialysis which has received much development in the past years, has been also presented. Keywords: Electrodialysis; Permselective membranes Electrodialysis with ion exchange membranes represents one of the most important membrane methods, which deals with the problems of desalination of salted waters, waste water minimization, production of ultra-pure water, concentration of dilute solutions, separation of electrolytes and non-electrolytes and with the production of acids and alkalis from their salts [1]. Electrodialysis is a well proven technology with a multitude of systems operating worldwide. In Europe electrodialysis dominates as a desalting process with total plant capacity exceeding that of reverse-osmosis and distillation [2]. Electrodialysis *Corresponding author. Fax: +49 345 5527163. 0376-7388/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S 0 3 7 6 - 7 3 8 8 ( 9 7 ) 0 0 149-X is also applied for whey-, organic acid- and sugar demineralization, amino acid and blood treatments, mineral acid concentration, preparation of isotonic solutions and wine stabilization. The deep ecological aspect of this method implies favourable forecasts for its future. In 1995 the volume commemorating the 100th issue of the Journal of Membrane Science pleased its readers through the publication of classical works on membrane methods but unfortunately, there was no mention of electrodialysis. However, the editor of this special issue, K.W. B6ddeker [3], noted the start of development of electrodialysis in the 1930s, remembering the work of Meyer and Strauss [4] in which the basic principles of modern electrodialysis had been proposed. 36 V.A. Shaposhnik, K. Kesore/Journal of Membrane Science 136 (1997) 35-39 Fig. 1. Scheme of the first electrodialysis apparatus. [8]. Prognosing the future is, first of all, an operation on the past. The bigger the period of time analysed, the more exact the result we can achieve. In relation to this, we would like to focus on the fact that electrodialysis has a much earlier history than that usually acclaimed by several authors. Electrodialysis is a combination method. One of its components is dialysis, proposed for the separation of water and alcohol first by Nollet [5] and later on for the separation of true and colloidal solutions by Graham [6]. The other component is electrolysis [7]. Electrodialysis as a method combining electrolysis and dialysis was proposed for the first time in 1890 by Maigrot and Sabates [8]. The aim of their work was to demineralize sugar syrup. Fig. 1 shows the scheme of the first electrodialysis apparatus. The frames were made out of wood, the plastic age lying still in future then. The electrodes were made out of carbon and permanganate paper serves as membrane. A direct electric current was supplied by a dynamo. The middle electrode acted as the common anode. Sugar syrup was poured through the anodic compartment. On turning on the dynamo potassium, sodium, magnesium and calcium cations were carried away by the electric current from the anodic compartment to the cathodic one. This resulted in the purification (demineralization) of the sugar syrup in the anodic compartment. In order to prevent the precipitation of sparingly soluble hydroxides, the reaction medium was controlled using litmus paper. The electrodialysis process was stopped when the litmus turned blue. Cassel and Kempe [9] applied this method to purify molasses, syrups and sugar solutions. The particularity in their work was the addition of salt solution to the cathodic solution, causing an alkaline reaction to take place under hydrolysis. This, in turn, prevented the hydrolysis of the desired products by the acids formed during the anodic reaction. However, the term 'electrodialysis' was not used in the patents considered above. It was proposed for the first time in the patent of Schollmeyer in 1900 [10], whose aim was to purify sugar syrup through the same method but using soluble zinc or iron anodes with simultaneous ozonation of the solutions. Kollrepp and Wolf [11] continued to use the term electrodialysis in their patent describing an improvement of the method for the purification of sugar syrup through the solubility of a sparingly soluble salt of lead, obtained during the use of a soluble lead anode. The first article about electrodialysis which appeared in a scientific journal was published in 1903 by Morse and Pierce [12]. Evaluating the first works on electrodialysis, Schlrgl [13] assumed that uncharged and non-selective membranes were used there. An analysis of those publications allows us to state that the membranes used had a small concentration of fixed ions and were still very far from ideal selective membranes. But they were not totally inert. New ideas came from the biologists Loeb and Beutner [14], who discovered the selective permeability of apple skin to cations during a study on the dependence of electrode potentials from the concentration of electrolyte solutions. They demonstrated that the nature and type of the anion did not influence the magnitude of the electrode potentials, but at the same time the charge number and type of cations caused a significant impact on it. Remembering the old apple which was picked by Eva from the tree of knowledge and the one which brought Newton to the universal law of gravitation, we can conclude that those wishing to make beautiful discoveries must put their attention first of all on the wise apple. Studying the flow of a direct current through membranes of collodion, permanganate-impregnated paper and gelatine, Bethe and Toropoff [15] found that there was a deviation from neutrality in the solution at the mem- V.A. Shaposhnik, K. Kesore/Journal of Membrane Science 136 (1997) 35-39 brane surface. We would like to put some more light on this acidification found at the cathodic side and on the alkalination occurring at the anodic side. Today, in view of modem representation these results can be interpreted as the exceeding of the limiting current density on the membrane, proving the existence of a difference in the transport numbers of ions in the membrane and in the solution. The excess of the electrical current over the limiting value is transferred by hydroxonium ions, formed during the non-reversible dissociation of water molecules at the solution/ membrane interface. This causes a decrease in the pH of the diffusion boundary layer at the cathodic side and an increase in the pH at the anodic side. As such, this gives us the base to make conclusions about the selective permeability of these membranes for cations. Furthermore, Bethe and Toropoff found that the walls of the pores have non-mobile negative charges and that there was an excess of mobile charges inside the pores, compensating the charges of the non-mobile ones. Indeed, the mobile ions carry the electrical charges through the membrane under the application of a gradient of an electric potential across the membrane system. The synthesis of semi-permeable membranes was a first related to trials dealing with the modelling of biological membranes. It was easier to measure the transport number, electrical conductivities and membrane potentials for synthetic membranes. The pioneering start of research on model membranes was laid down by Michaelis, studying the properties of collodion membranes [1,16]. The membranes used in his early works had low electro-chemical activities. A KAKA I-- Q I • 0 • oi o • © • o! • o • o o • o • 0 • °I° ! • 0 i I • a 37 Nevertheless, they were more selective in respect to cations, having weak acidic carboxylic ions as ionogene groups. Anion selective membranes were obtained during the adsorption of proteins on collodion membranes. Generalizing the results of his precedents and of his own experiments, Teorell [17-19] developed the theory of charged membranes. According to this theory a selective membrane is considered as a homogeneous phase in which the fixed ions, mobile counter-ions and the mobile co-ions having the same charge sign as the fixed ones are uniformly distributed. Under this consideration, the membranes selectively permeable to cations had negatively charged fixed ions and membranes selectively permeable to anions had positively charged fixed ions. The concentration of co-ions was limited by the electrostatic repulsion from the fixed charges of the membrane, which corresponded to the earlier thermodynamical theory of membrane equilibrium developed by Donnan [20]. The further development of this theory was practised by Meyer and Sievers [21], Sollner [16] and Schl6gl [13]. Theoretical research on the electrochemistry of membranes opened the way for the progress in electrodialysis. The use of the first electrodialysers with 3 compartments emerged in the works of Pauli [22]. The mixture to be separated was fed into the middle compartment from which the cations migrated into the cathodic compartment and anions into the anodic compartment. The first monograph on electrodialysis came out, explaining clearly the electrodialysis process [23]. Nevertheless, only one type of membrane was used in the electrodialysers of that time. A KA KA Q b Fig. 2. Migration of ions in a system of alternating membranes, a - before the action of an electric current, b - after the action of an electric current, where • represents an anion and 0 a cation. [4]. 38 V.A. Shaposhnik, K. Kesore/Journal of Membrane Science 136 (1997) 35-39 Manegold and Kalauch [24] used for the first time permselective anion exchange and cation exchange membranes in a 3-compartment electrodialysis apparatus. Desalination took place in the middle compartment. An outstanding work by Meyer and Strauss [4], in which the properties of alternating cation exchange and anion exchange membranes were presented. Fig. 2 shows the process of ion transport in a 6compartment electrodialysis cell. In (Fig. 2 (a)) during the absence of the action of an electric current, there is an uniform distribution of cations and anions in the compartments of the apparatus. Under the application of an electric field, with the passage of a direct electric current through the solution, a beautiful symmetrical process starts taking place. During this process the cations move towards the cathode and the anions in the opposite direction towards the anode. For example, with numbering of compartments done from left (anodic compartment) to right, the anions from the second compartment migrate towards the anodic compartment through the anion-permeable membrane and the cations migrate towards the cathode through the cation-permeable membrane. As a result of this, desalination takes place in the second compartment. During the electro-migration towards the cathode, cations from compartment 2 meet an anion-permeable membrane in their way which separates compartments 3 and 4. This membrane stops further migration of the cations towards the cathode. Consequently, the cations gather in the solution in compartment 3. On the other side there is an electromigration of anions from compartment 4 into the solution in compartment 3. This electro-migration is limited by the presence of a cation-permeable membrane separating compartments 2 and 3. Consequently, there is concentrating of ions in the compartment 3. In this way, the multi-compartment electrodialysis of Meyer and Strauss [4] allowed to carry out the concentration as well as the desalination of electrolyte solutions without the danger that the products enter into a chemical reaction with the electrodes in the electrodialyser. Even more important to note is that the same expense of electrical energy is needed for carrying out the electrode processes in the multi-compartment electrodialyser as in the three compartment apparatus. Subsequently this led to an increase in the number of compartments in the apparatus with alternating cation-permeable and anion-permeable membranes to hundreds of membranes and compartments, under which all the even-numbered compartments fulfilled the function desalination and all the odd ones- that of concentrating, in respect to the above described electrode positions and numbering. The realization of the principle of alternating cation-permeable and anion-permeable membranes in multi-compartment electrodialysis became possible after the manufacture of selective membranes from ion exchangers. First, it started after the work of Juda and Mc Rae [25] and also simultaneously after that of Kressman [26]. Soon after this the basic principle of electrochemistry of ion-exchange membranes and the basic directions of electrodialysis with ion-exchange membranes were worked out: purification, desalination of weak electrolytes with low dissociation constants, and of non-electrolytes; concentration of solutions; synthesis of acids and bases from their salts; reactions of double chemical conversion; methods for the separation of ions according to their mobilities, magnitude and sign of charge and to their differences in the capabilities to form complexes [1]. Soon, a very fruitful idea of filling the compartments of the electrodialyser with ion exchange granules was born, which principally expanded the first and original concepts about the possibilities of electrodialysis, allowing to work in economically and ecologically desirable improved ways for the deep desalination of dilute solutes [27,28]. That was relatively a short period, but a period of high stress and breakthroughs, during which the most important versions of the application electrodialysis were worked out. In this way ended the early period of development of electrodialysis - a method which has to occupy a place among the most important and determining technologies of the twenty-first century. References [1] J.R. Wilson (Ed.), Demineralization by Electrodialysis, Butterworths Scientific Publications, London, 1960. [2] Wagnick Consulting 1990 International Desalting Association Worldwide Desalting Plants Inventory, Report No 11, 1990. [3] K.W. B6ddeker, Commentary: Tracing membrane science, J. Membrane. Sci., 100 (1995) 6548. V.A. Shaposhnik, K. Kesore /Journal of Membrane Science 136 (1997) 35-39 [4] K.H. Meyer and W. Strauss, La permeabilit6 des membranes, VI, Sur la passage du courant electrique a travers des membranes selectives, Helv. Chim. Acta, 23 (1940) 795-800. [5] J.A.(Abbe) Nollet, Recherches sur les causes du boullonnement des liquides, Histoire de l'Academie Royale des Sciences, Paris, 1752, 57-104. [6] T. Graham, On the law of the diffusion of gases, The London and Edinburgh Philosophical Magazine and J. of Sci., 2 (1833) 175-190, 269-276, 351-358. [7] W. Nicholson, A. Carliebe and W. Cruichank, Experiments in galvanic electricity, Phil. Mag., 7 (1800) 337-347. [8] E. Maigrot and J. Sabates, Apparat zur L~iuterung von Zuckers~iften mittels Elektrizitiit, Germ. Pat. Nr. 50443, 1890. [9] G.E. Cassel and D. Kempe, Verfahren: Melasse, Sirop und andere Zuckerlrsungen elektrolytisch zu reinigen, Germ. Pat. Nr. 78972, 1894. [10] G. Schollmeyer, Reinigung von Znckersaften durch Elektrodialyse und mit Ozon, Germ. Pat. Nr. 136670, 1902. [11] A. Kollrepp and A. Wolf, Verfahren zur elektrolytischen Reinigung zuckerhaltiger L~Ssungen unter Zusatz leicht angreifbarer Blei- oder Zinkverbindungen, Germ. Pat. Nr. 136670, 1902. [12] H.N. Morse and J.A. Pierce, Z. Phys. Chem., 45 (1903) 589. [13] R. Schl6gl, Stofftransport durch Membranen, Dr. Dietrich Steinkopf Verlag, Darmstadt, 1964. [14] J. Loeb and R. Beutner, Biochem. Z., 41 (1912) 1-6; 44 (1912) 303-309; 51 (1913) 300-308. [15] A. Bethe and T. Toropoff, f2ber elektrolytische Vorg~nge an Diaphragmen, Z. Phys. Chem., 88 (1914) 686-742. [16] K. Sollner, The early development of the electrochemistry of polymer membranes, in: E. Selegny (Ed.), Charged Gels and [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] 39 Membranes, Part, D. Reidel Publ.Comp., Dordrecht-Boston, 1976. T. Teorell, An attempt to formulate a quantitative theory of membrane permeability, Proc. Nat. Acad. Sci., Wash., 21 (1935) 282-285. T. Teorell, Zur quantitativen Behandlung der Membranpermeabilit~it, J. Elektrochem., 55 (1951) 460-469. T. Teorell, Transport processes and electrical phenomena in ionic membranes, Prog. Biophysics., 3 (1953) 305-369. EG. Donnan, Theory of membrane equilibrium and membrane potential in the presence of non-dialysing electrolytes. A contribution to physical-chemical physiology, Theorie der Membrangleichgewichte und Membranpotentiale bei Verhandsein von nicht dialysirenden Elektrolyten, Ein Beitrag zur physikalisch-chemischen Physiologie, Z. Elektrochem. Angewandte Phys. Chem., 17 (1911) 572-581. K.H. Meyer and J.F. Sievers, La permeabilit6 des membranes, Helv. Chim. Acta, 19 (1936) 649~77. W. Pauli and E. Yalko, Elektrochemie der Kolloiden, J. Springer, Wien, 1929. P.H. Prausnitz and J. Reitst~Stter, Elektrophorese, Elektroosmose, Elektrodialyse in Fliissigkeiten, Steinkopf, Dresden, 1931, E. Manegold and C. Kalauch, Kolloid. Z., 86 (1939) 93. W. Juda and W.A. Mc Rae, Coherent ion exchange gels and membranes, J. Amer. Chem. Soc., 72 (1950) 1044-1053. T.R.E. Kressman, Ion exchange resin membranes and resin impregnated filter paper, Nature, 165 (1950) 568-574. W.R. Walters, D.W. Weiser and L. Marek, Concentration of radioactive aqueous wastes, Ind. Eng. Chem., 47 (1955) 61-67. E. Glueckauf, Electro-deionization through a packed bed, Brit. Chem., 4 (1959) 646-651.
