The electrodialysis setup consists of: one ED cell, one DC power, one brine tank, one power tank, one electrode rinsing tank, three centrifugal pumps (P = 84 W, total head = 4.2 m) each equipped with a flow meter and three valves to control the supply flow rate. Fig. 2 shows a simplified diagram of the electrodialysis system operating in continuous mode.Fig. 2 Schematic of the electrodialysis system used in this study. The electrodialysis operation was performed on a laboratory stack “PCCell ED 64 002” provided by PCA-Polymerchemie Altmeier GmbH and PCCell GmbH, Heusweiler, Germany. As shown in Figure 3, the ED cell is equipped with ion exchange membranes (cation and anion), spacers, and a pair of electrodes (anode and cathode). Both electrodes are made of Pt/Ir-coated titanium. The membranes and spacers are stacked between the two blocks at the end of the electrode. Plastic separators are placed between the membranes to form flow paths for the diluted and concentrated streams. These spacers are designed to minimize boundary layer effects and are arranged in the stack so that all diluted and concentrated flows are brought together separately. In this way a repetitive section called a pair of cells is formed; It consists of a cation exchange membrane, a dilute flow spacer, an anion exchange membrane and a concentrated flow spacer. In this work, experiments were conducted with this stack equipped with three cation exchange membranes (CEMs) and two anion exchange membranes (AEMs). For each membrane, the active surface area is 0.0064 m2 and the width of the flow channel between two membranes is 0.5 mm.Fig. 3 Schematic of the ED cell used in this study. PC-SK standard cation exchange membranes and PC-SA standard anion exchange membranes are used in the stack. Information provided by the manufacturer... middle of the sheet... the applied potential, I the applied current, V the diluted flow volume and t is the time.2.5.5. Current CE efficiency. The number of moles of an ion crossing the membrane from the diluted to the concentrated solution during the time t is compared with the number of Faradays involved in the operation. The ratio between the two numbers is called current efficiency. Current efficiency is an important parameter that determines the optimal range of applicability of electrodialysis. It is a measure of how effectively ions are transported across ion exchange membranes for a given applied current. It is calculated using the following equation [20, 21]:CE=(∆N_A.F)/QWhere NA is the equivalent number of A transferred per cell in the time interval t, Q the current quantity supplied to the system in the same time and F is the Faraday constant (96 485 A s mol−1).