Format

Send to

Choose Destination
Water Res. 2017 Sep 1;120:229-237. doi: 10.1016/j.watres.2017.05.009. Epub 2017 May 5.

Comparison of Faradaic reactions in capacitive deionization (CDI) and membrane capacitive deionization (MCDI) water treatment processes.

Author information

1
School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
2
School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: di.he@unsw.edu.au.
3
School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: d.waite@unsw.edu.au.

Abstract

Capacitive deionization (CDI) and membrane capacitive deionization (MCDI) are the most common cell architectures in the use of CDI for water treatment. In this work, the Faradaic reactions occurring in batch-mode CDI and MCDI processes were compared by investigating the variation of H2O2 and dissolved oxygen (DO) concentrations, pH, conductivity and current during charging and discharging under different charging voltages. During charging, the H2O2 concentration in CDI increased rapidly and then decreased while almost no H2O2 was generated in MCDI due to the inability of oxygen to penetrate the ion exchange membrane. Chemical kinetic models were developed to quantitatively describe the variation of H2O2 concentration and found to present satisfactory descriptions of the experimental data. The pH drop during charging could be partially explained by Faradaic reactions with proton generation associated with oxidation of the carbon electrodes considered to be the major contributor. The electrode potentials required for the induction of Faradaic reactions were analyzed with this analysis providing robust thermodynamic explanations for the occurrence of carbon oxidation at the anode and H2O2 generation at the cathode during the ion adsorption process. Finally, electrochemically-induced ageing of the carbon electrodes and the resulting performance stability were investigated. The findings in this study contribute to a better understanding of Faradaic reactions in CDI and MCDI and should be of value in optimizing CDI-based technologies for particular practical applications.

KEYWORDS:

Capacitive deionization; Electrode potential; Faradaic reactions; Ion exchange membrane; Kinetic model

PMID:
28500988
DOI:
10.1016/j.watres.2017.05.009
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center