Review on carbon-based electrode materials for application in capacitive deionization process

Most of the electrochemical studies related to porous carbon electrodes are those which can be used for either electrostatic energy storage or for energy conversion [using electrical double layer capacitor (EDLC)]. The techniques, such as electrodialysis, membrane filtration, advanced oxidation process, thermal evaporation, can be used now-a-days to treat salty water. Among which, capacitive deionization (CDI) has emerged as a novel cost effective and environment friendly desalination technology. CDI process involves the removal of inorganic ions from the salty water by applying an electrical potential between two porous carbon electrodes. Because of the passage of electrical potentials in the system, the unwanted ions present in the water sample will be adsorbed on the electrode surfaces. Hence, the electrodes which are having high surface area can exhibit higher desalination capacity. In this article, the application of various carbon-based composite electrode materials such as activated carbon and PVDF composite, carbon–metal oxide composite, carbon–CNT composite, carbon–polymer composite and carbon sheet (carbon aerogel, activated carbon cloth) in CDI process is systematically reviewed and presented. CDI process is being developed now-a-days especially toward commercialization in treating the brackish water.