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 the ion-exchange membranes. Applying an electric field with special pulse characteristics can diminish the effect of the concentration polarization. A theoretical analysis is carried out for galvanostatic and potentiostatic pulse regimes. The time dependencies of the extent of the concentration polarization near the membrane surface during the pulse are described theoretically for both pulse regimes and a qualitative discussion of the pause duration is presented. The main characteristic of the non-stationary process is the 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 than this transition time. Experimental results are quoted that qualitatively support the model predictions. It is shown that the desalination can be intensified several times, depending on the pulse-pause characteristics. (C) 2001 Elsevier Science B.V. All rights reserved.