(545al) Modeling the Ion Transport and Adsorption in a Capacitive Deionization Cell

Capacitive Deionization (CDI) is a promising technology for removing salts from brackish water by applying an electric field to drive ionic species toward oppositely charged electrodes. Thus ions are stored within the electrical double layer (EDL) formed near the surface of the electrode during charging process and pushed back to the bulk solution during discharging process, respectively. In this study, the CDI process is analyzed from both equilibrium state and transient transport state. A one-dimensional overlapped EDL adsorption model with changing stern layer thickness versus concentration was developed and the corresponding isotherm fit the experimental data well. A two-dimensional transient transport model incorporated with the adsorption model was built to study the diffusion, advection and electromigration of the ionic species in channel and electrode macropores and captured the ion adsorption dynamics based on changing inlet concentration, flow rate as well as voltage in the CDI system. What’s more, the improvement in performance associated the use of spacers to aid mixing was explored with the model. Various operational regimes and the resulting power requirements were also evaluated to optimize the system.