Effect of electrode properties and operational parameters on capacitive deionization using low-cost commercial carbons

The unequal distribution of the water resources warrants a search for more energy efficient water treatment technologies. In this regard, capacitive deionization (CDI) could play a leading role particularly in the case of brackish water desalination. In this work, inexpensive materials that are commercially available were investigated for being used as electrodes in CDI. After physical and electrochemical evaluation, activated carbon (AC) demonstrated superior performance compared to the different fabrics tested. Hereafter, a factorial design of experiments was used to investigate the effect of cell potential, mass of AC (m_AC), carbon black, and interparticle porosity on ion removal, charge efficiency and energy consumption. The results showed that neither carbon black nor macroporosity had a single effect on electrode performance. An interaction effect of macroporosity and m_AC was found to be beneficial in terms of ion electrosorption for thick electrodes. An additional evaluation concerning the role of electrode thickness revealed that an increase in thickness translated into an increase in the total salt removed and a reduction in ion removal per mass of electrode. In addition, while electrosorption kinetics were found to be independent of the AC thickness, slow desorption kinetics were detected for the thicker electrodes.