Adsorption behavior of powdered activated carbon to control capacitive deionization fouling of organic matter

Abstract

Capacitive deionization (CDI) is a promising desalination technology, but it suffers from serious irreversible fouling caused by the presence of organic matter, which severely reduces the desalination performance. In this research, powdered activated carbon (PAC) was used to reduce the fouling caused by the presence of humic acid (HA). Due to the effective removal of HA by PAC adsorption, HA deposited onto the CDI electrode was reduced by about 40%. Desalination performance of CDI was improved when PAC adsorbed HA entered into the CDI system, resulting in the removal of HA under the action of an electric field in the CDI system, thereby alleviating the irreversible CDI fouling caused by HA. Alternatively, PAC entering the CDI system improved electrical conductivity due to the formation of electrical double layers (EDLs) in the flow path, thereby reducing the internal resistance of CDI system to increase the capacitance of CDI system. The presence of PAC in the CDI system was responsible to reduce the deposition of organic matter onto the electrode as well as the resistance of CDI system, resulting in optimized specific surface area and conductivity to improve the CDI performance.