Lithium bromide is a white powder with bitter taste and soluble in water with properties such as chemical stability and water absorbing. The most important commercial application of this chemical is as working fluid in absorption chillers. Application of aqueous solution of lithium bromide is wider than other working fluids due to forming strong binding between lithium ions and water molecules and therefore high water absorbing property. Very high heat of vaporization of water and non-volatility of LiBr are two specific features of LiBr/H 2 O solution as well as being expensive, corrosive to some metals, and readily prone crystallized at the high concentration. In the absorption chillers, pollution of lithium bromide solution with water leads to lowered concentration of lithium bromide and increasing the amount of sodium ions in the solution which makes the working fluid in the chillers useless. Therefore, the working fluid should be replaced by fresh and expensive fluid. On the other hand, wasting the polluted solution is not logical due to economic and environmental reasons and it makes it necessary to find a proper way to reuse the polluted solution. To this aim, lithium and sodium ions must be relatively separated which is an impossible task by conventional methods such as chemical precipitation and centrifuging due to very close and similar chemical properties of these two ions. The subject of this research was relative separation of lithium and sodium ions and recovery of lithium ions in the form of lithium hydroxide by implementing electrodialysis method. For these purpose a four-compartment electrodialysis cell was designed and built. In the first step some experiments were carried out to investigate the effects of some operating parameters such as applied voltage, initial lithium bromide concentration, and process time. The objective functions were lithium ion recovery, specific energy consumption, lithium ion permeation flux, current efficiency for the lithium ions, ratio of lithium to sodium ions concentrations in the cathodic chamber, change in the lithium ion concentration at any time respect to the initial concentration in the cathodic chamber (C/C0), and current density. The obtained results showed that increasing the applied voltage led to increase in the recovery of lithium ion as in the form of lithium hydroxide, lithium ions permeation flux, concentration ratio of lithium to sodium ions the cathodic compartment, lithium ion concentration, and current density. Also, higher specific power consumption was needed for higher voltages. Also lithium ions permeation flux, lithium ion concentration at any time over initial feed concentration (C/C 0 ) and current efficiency were augmented with increasing the initial feed concentration. However, lithium hydroxide recovery, concentration ratio of lithium to sodium ions in the cathodic compartment, and specific power consumption all decreased with increasing the initial feed concentration. Maximum recovery of about 20% was obtained for the feed solution containing 13900 ppm lithium ion by applying voltage of 7 volt to the cell for duration of 6 hours. It is worth mentioning that by applying a voltage of 7 to the cell the concentration ratio of lithium to sodium ions reached to about 88.5 and 73 for the feed solutions with initial lithium concentrations of 27800 and 13900 ppm, respectively. These values are well above in comparison the ratio of 58b for the fresh and unpolluted lithium bromide solution. In the second stage of the work, factorial method was used for statistical investigation on the effects of operating parameters on lithium ions recovery and concentration ratio of lithium to sodium ions in the cathodic chamber. 3 levels were selected for operating parameters including voltage (in the range of 3-7 volts), lithium ions concentration in the feed solution (in the range of 13900-27800 ppm), and time (in the range of 120-360 min) to design the experiments. The 2FI models were established for the two above mentioned objective functions in the terms of operating parameters with determination coefficient R 2 of 0.9634 and 0.9764, respectively, indicating that the offered models are successful to describe the lithium ions recovery and ratio of lithium to sodium ions concentration. Analysis of variance (ANOVA) showed that voltage and time were the most influent parameters on the lithium ions recovery and concentration ratio of lithium to sodium ions with Prob F