Theory of Water Desalination by Porous Electrodes with Immobile Chemical Charge

• Published in: Colloid and interface science communications Vol. 9; pp. 1 - 5
• Main Authors: Biesheuvel, P.M., Hamelers, H.V.M., Suss, M.E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2015
• Subjects: Environmental Technology; Milieutechnologie; Physical Chemistry and Soft Matter; Sectie Milieutechnologie; Sub-department of Environmental Technology
• ISSN: 2215-0382; 2215-0382
• DOI: 10.1016/j.colcom.2015.12.001

In capacitive deionization (CDI), water is desalinated by storing ions in electrical double layers (EDLs) within the micropores of charged porous carbon electrodes. Recent experiments using chemically modified electrodes have shown differing, novel phenomena such as “inverted CDI,” “enhanced CDI,” and “inversion peaks.” We here present an EDL and dynamic model which includes immobile chemical charge in the micropores and show that the models predict these disparate experimental observations. Our model also makes predictions for a previously undiscovered operational regime with higher salt adsorption, which we term extended voltage CDI. [Display omitted] •Simple, extended electrical double layer theory developed for capacitive deionization (CDI).•Theory explains novel desalination regimes, such as inverted operation of CDI cells.•Novel regimes explained in terms of electronic charge compensation mechanisms in carbon micropores.