Capacitive deionization characteristics of nanostructured carbon aerogel electrodes synthesized via ambient drying

Abstract

RF (resorcinol formaldehyde) organic aerogels were cost-effectively prepared by solvent exchange using acetone and then ambient drying of RF wet gels obtained from the sol–gel method of the starting solution of RF. The carbon aerogel electrodes for the capacitive deionization (CDI) process with high specific surface area (∼610 m 2/g), high specific capacitance (∼220 F/g), high porosity (∼80%), low bulk density (∼0.50 g/cm 3), and high electrical conductivity (∼13.2 S/cm) have been synthesized via pyrolyzing RF organic aerogels at 800°C in nitrogen atmosphere. The CDI unit system containing a pair of carbon aerogel electrodes showed the maximum ion removal efficiency when the 50 mg/L NaCl solution was recycled at the volume flow rate of 400 mL/min under the applied voltage in the range of 1.5–1.7 V. Under the optimum operating conditions of the CDI unit system, the NaCl removal efficiency of the CDI stack system composed of 6 unit cells was about 92.8% and 97.6% at 1.5 and 1.7 V, respectively. It was evaluated that the CDI process using carbon aerogel electrodes promised to be an effective technology for desalination.