Electrodeionization (EDI) technology combines the operation principle of both ion exchange and electrodialysis in one single unit and overcomes the disadvantages of either unit. This technology has been widely used fit the production of ultrapure water due to its better performance and economical operation at low feed concentrations. As it result, there have been several studies that deal with application of this technology for the removal of ions from water. However, except for a few studies, most of the reported works deal with the experimental study of EDI. This study deals with the development of a mathematical model for deionization of electrolyte solutions containing more than one ion and ions that are multivalent in nature. The model validity is verified by comparing the results with a few experimental observations. This is followed by a sensitivity study of the EDI unit to explore the effect of various operating and system parameters on the ion removing ability of the EDI unit. Consequently, a systematic optimization exercise that can simultaneously handle more than one objective for superior system performance of the experimental unit is demonstrated. Due to the optimization study, it is shown that many times EDI is not operated at optimized conditions and decreasing the flow rate, among other variables, might have a significant effect oil system performance.