Designing capacitive deionization module for water treatment systems at car washers

Abstract

It is impossible to effectively use water with a high salt content at car washes. In many places, access to water with a high salt content is almost unlimited but its utilization requires deionization. For this purpose, several methods are used, the main of which are reverse osmosis, electrodialysis, ion exchange methods, and distillation. However, they have significant drawbacks. Recently, the technology of capacitive deionization of water has been widely used, based on the removal of salt ions from the solution during the charge/discharge of "double" electric layers of carbon materials with a significant active surface (800‒2,000 m2/g). Theoretically, this process should be more energy efficient by using a low potential voltage (1–2 V). This paper considers the interrelation of physical parameters that affect the process of capacitive deionization of water. The dependences of voltage drop on serial internal resistance on different concentrations of sodium chloride and the distance between electrodes for electrodes based on the material SAUT-1S (Belarus) have been investigated. It is shown that the main contribution to the sequential internal resistance is introduced by the resistance of the electrolyte. As the distance between the electrodes increases, the voltage drop on the serial internal resistance increases linearly. A decrease in the concentration of ions leads to a decrease in the conductivity of the solution, which causes an increase in energy consumption and a decrease in the efficiency of sorption. It has been demonstrated that the voltage drop at the serial internal resistance when the voltage on the electrodes is limited, which is set in order to avoid the transition of the electrode charging mode to the electrolysis of water, causes a significant drop in the efficiency of the capacitive deionization process