Characterization of electroregeneration and determination of optimal current density in continuous electrodeionization

Electrical impedance spectroscopy was used for the characterization of electroregeneration in a continuous electrodeionization (CEDI) system packed with cation-exchange resin (CIX). CEDI process usually operates in two regimes of enhanced transfer and electroregeneration. The current efficiency decreased in the second regime of a CEDI system due to the water dissociation. Therefore, it is necessary to minimize the second regime to maximize the current efficiency by controlling the operating parameters even though the second regime is essential for regeneration of the resin. It was suggested to monitor the ionic state of the bed during the operation by observing current distribution along the column. The measurement of the resistance of CIX beads at high frequency, based on the equivalent circuit, provided information on the extent of electrical regeneration of the bed. The optimal current density was estimated at the minimized area of second regime, and the operation at the optimal current density showed the 100% of metal removal, indicating the effectiveness of this method.