A Comparative Study between Membrane Capacitive Deionization and Capacitive Deionization from Isotherms and Kinetics

Membrane capacitive deionization (MCDI) is a promising technique to achieve the desalination. This novel technique can largely improve the desalination efficiency of capacitive deionization (CDI) by introducing ion-exchange membranes into CDI. This paper presents a comparative study on the electrosorptive performances of CDI and MCDI based on single walled carbon nanotubes electrodes in NaCl solution from electrosorption isotherm and kinetics analysis. It was found that MCDI exhibits a higher salt removal efficiency of 98% than CDI (52%) and the ions sorption behavior follows Langmuir isotherm in both CDI and MCDI, indicating the monolayer sorption. Furthermore, the kinetics analysis shows that the ion-exchange membranes can speed up the ion transport during the electrosorption process due to restricted co-ions expulsion impaction.