Desalination of brackish water by electrodeionization: Experimental study and mathematical modeling

Abstract

Electrodeionization (EDI) is an advantageous technology for desalination of waters with the range of salinity found in brackish water. Although modeling can help to understand the behavior of EDI cells, no reliable models connecting relevant operational variables have been published so far. Thus, this paper presents the experimental study and the mathematical modeling of an electrodeionization process used for the desalination of brackish water. The desalination process was carried out in a 4-compartment laboratory EDI cell. The model developed proposes an approach to the transport of ions in the liquid flowing in the mixed-bed resin's interstitial space. This transport is driven by the potential gradient in the liquid phase, formed by the different electric potential of cation- and anion-exchange resin particles and the Donnan potential at the interface. The model is used to analyze the current density distribution in the EDI cell and its effect on ion removal and performance to identify ineffective regions of the cell. The comparison of model calculation with experimental data shows the model to be capable of describing the effect of concentration (0.01 and 0.02 M) and cell voltage (7, 10.5 and 14 V) changes on current density and desalination rate.