Study of the linearity of the voltage–current relationship in ion-exchange membranes using the network simulation method

The conditions of linearity of the current–voltage relationship in ion-exchange membrane systems have been investigated using the network simulation method. A network model is proposed for the Nernst–Planck and Poisson equations describing the ionic transport through an ion-exchange membrane and the two diffusion boundary layers on both sides of the membrane. With this model and the electric circuit simulation program PSPICE™, a decomposition into Fourier components of the electric current–time response, which follows the application of a sinusoidal-shaped electric potential, is obtained. The results reveal a considerable influence of the membrane fixed charge concentration on the amplitude of the different harmonics.