Electrical Resistance of Ion Exchange Membranes

The electrical resistance of an ion exchange membrane is an important property that is expressed as electrical resistance per unit area (Q cm2). Though electrical resistance is usually measured in sodium chloride or potassium chloride solution, that of membranes changes remarkably with the species of counter-ions.1 Table 

In general, a standardized solution and standard conditions are used to compare the electrical resistance of various membranes. The electrical resistance decreases 

Solution HCl NaCl KCl MgCl2 CaCl2 SrCl2 BaCl2 NaCl-CaClf 

The electrical resistance of the membrane measured by the ac method and that measured by direct current are approximately the same except for membranes with anisotropic structures (a membrane for which one surface has been modified). 

5 N NaCl has been used. Conversely, for brackish water desalination a 0.1 N NaCl/membrane/0.2 N NaCl may be used. The membrane potential is measured using a potentiometer or high impedance voltmeter (more than 2 MQ). In general, the membrane potential is high when the ratio of the concentration of the concentrated side solution to that of the dilute side solution is high and becomes low when salt solutions of high concentration are used. Transport numbers are calculated by Eq. (4.1) when a 1 1 valence electrolyte solution is used and the potentials between the probe electrodes and their ambient solutions are subtracted  

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K. Urano, Y. Masaki and Y. Naito, Increase in electric resistance of ion-exchange membranes by fouling with naphthalenemonosulfonate, Desalination, 1986, 58, 177. 

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