Capacitive deionization characteristics of compressed granular activated carbon

Abstract

• Granular activated carbon (GAC) without additives is used for the electrode of CDI. • Applying pressure to the GAC is effective in decreasing its electric resistance. • The salt adsorption capacity of this CDI is comparable to that of existing CDI cells. • The charge efficiency of this CDI is also comparable to that of existing CDI cells. Capacitive deionization (CDI) has attracted a lot of attention in recent years as an energy-efficient and cost-effective desalination technology. In addition to its low cost, granular activated carbon (GAC) satisfies the general requirements for the CDI electrodes. In this study, the possibility of using GAC for CDI electrodes was investigated experimentally. When GAC is packed into a CDI cell as the electrodes without pressure, the amount of ion removal was small due to high electric resistance of the GAC electrodes. When the GAC was then compressed between the current collectors of a cylindrical reactor, the amount of ion removal improved significantly due to a drastic decrease in the electric resistance. In consideration of the ohmic drops in the CDI cell with compressed GAC, the effect of applied voltage on salt adsorption capacity (SAC) was also studied experimentally. It was shown that the SAC reached 9.8 mg/g at 2.0 V. This SAC is comparable to other CDIs in the previous studies. Therefore, our CDI cell with compressed GAC is a potential alternative to conventional methods as a cost-effective desalination technology.