A capacitive deionization system with high energy recovery and effective re-use

We have developed a simple and inexpensive hydrophilic activated-charcoal based electrode for a CDI (capacitive deionizer) cell system and examined its physical and electrochemical properties. In this study, the ion adsorption/desorption mechanisms of a CDI stack equipped with the developed activated-charcoal electrodes, having either uni-polar or bi-polar circuit structures, were evaluated. The experimental results showed that the CDI stack with a bi-polar circuit consumes lesser energy than that with a uni-polar connection. A combined flow-through and batch processing operation for ion adsorption and desorption processes was also systematically evaluated. Furthermore, the energy recovery by discharging the stored energy of the ion desorbing electrode pair to another pair for ion adsorption by switching four-CDI cells for both the discharge and the charge sides was 70% at the maximum.