Intensification of electrodialysis by applying a non-stationary electric field

Electrodialysis is an effective method of water desalination. However, the efficiency of the method is limited by the concentration polarization of th e ion-exchange membranes. Applying an electric field with special pulse cha racteristics can diminish the effect of the concentration polarization. A t heoretical analysis is carried out for galvanostatic and potentiostatic pul se regimes. The time dependencies of the extent of the concentration polari zation near the membrane surface during the pulse are described theoretical ly for both pulse regimes and a qualitative discussion of the pause duratio n is presented. The main characteristic of the non-stationary process is th e transition time between the state without polarization and the state with stationary polarization. In principle, the electrodialysis process can be intensified significantly when the applied pulse is sufficiently smaller th an this transition time. Experimental results are quoted that qualitatively support the model predictions. It is shown that the desalination can be in tensified several times, depending on the pulse-pause characteristics. (C) 2001 Elsevier Science B.V. All rights reserved.