Capacitive deionization (CDI) is a promising technology to remove salts from saline water with low or moderate salt concentrations. In the CDI process, saline water containing at least 5 mM sodium chloride (NaCl) flows through a spacer channel between an electrochemical cell consisting of an anode and a cathode. As an externally applied voltage polarizes the charges on the electrodes’ surface, the cations and anions are attracted by the cathode and the anode, respectively, through electrostatic force. Desalinated water can be obtained from the effluent as the salts are adsorbed by the electrodes.
Porous activated carbon electrodes with nanometer micropores are commonly used for CDI because of their high specific surface area. Electrode charges, salt adsorption capacity, and applied voltage are the key properties of interest in CDI because they determine the desalination efficiency and energy requirement of the process.
The salts are adsorbed solely by capacitive storage in what’s known as the electrical double layer (EDL) at the electrode-solution interface without Faradaic reactions. The applied voltage perturbs ion concentrations and...
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