Efficient regeneration of activated carbon electrode by half-wave rectified alternating fields in capacitive deionization system

Capacitive deionization (CDI) is a promising technology for water desalination. An excellent desorption rate guarantees re-adsorption performance of CDI electrode in the following cycles. In this paper, we reported for the first time that the use of half-wave rectified alternating current (HWAC), a periodically changing electric field, improved electrodesorption in CDIs. Up to 90% of adsorbed NaCl can be released from activated carbon electrodes after HWAC (1.2 V, 1 kHz, 90 min) than 78% of direct current (DC, 1.2 V) powered systems, corresponding to a 79% current efficiency than 71% of DC. This was attributed to the elimination of capacitance in pores as well as the agitation of ions by the periodically changing electric field. Energy consumption per unit charge release decreased by 68% from 145 +/- 11 J/(mmol e(-)) of DC to 46 +/- 3 J/(mmol e(-)) of HWAC. Electrodesorption of MgSO4 and the mixture of NaCl/MgSO4 have similar results, indicating that the energy-saving strategy of HWAC was not affected by ionic charge or radius. These findings demonstrated that HWAC was a highly efficient waveform for maximizing the ion desorption from porous electrodes with a low energy requirement. (C) 2018 Elsevier Ltd. All rights reserved.