Electrode reactions and adsorption/desorption performance related to the applied potential in a capacitive deionization process

Abstract Desalination experiments were performed by constructing a capacitive deionization (CDI) unit cell with a carbon electrode prepared from activated carbon powder (ACP). Through CDI experiments, the mechanism of adsorption, desorption and electrode reactions were investigated by measuring conductivity, effluent pH, and the current passed through the cell under different electrode potentials. The salt-removal efficiency increased with increasing potential at the range of 0.8–1.5 V. Additionally, the pH of the solution varied significantly with a change in potential. At potentials less than 1.0 V, the pH increased due to the reduction of dissolved oxygen and the pH decreased at potentials over 1.2 V due to oxidation reactions at the anode. The change in current revealed that adsorbed ions were not completely desorbed and a fraction of ions were retained at the carbon electrode. These accumulated ions were re-adsorbed at the electrode surface when a potential was re-applied, which led to a decrease in the salt-removal efficiency of CDI.

[1]  Yongsoo Jeong,et al.  Nanoporous activated carbon cloth for capacitive deionization of aqueous solution , 2006 .

[2]  Chi-Woo Lee,et al.  Development of a carbon sheet electrode for electrosorption desalination , 2007 .

[3]  Joseph C. Farmer,et al.  Capacitive Deionization of NaCl and NaNO3 Solutions with Carbon Aerogel Electrodes , 1996 .

[4]  Chi-Woo Lee,et al.  Desalination of a thermal power plant wastewater by membrane capacitive deionization , 2006 .

[5]  Costas Tsouris,et al.  Electrosorption of ions from aqueous solutions by nanostructured carbon aerogel. , 2002, Journal of colloid and interface science.

[6]  Linda Zou,et al.  Ordered mesoporous carbons synthesized by a modified sol-gel process for electrosorptive removal of sodium chloride , 2009 .

[7]  Jae-Hwan Choi,et al.  Fabrication and characterization of a porous carbon electrode for desalination of brackish water , 2009 .

[8]  Zhuo Sun,et al.  Electrosorptive desalination by carbon nanotubes and nanofibres electrodes and ion-exchange membranes. , 2008, Water research.

[9]  Min-Woong Ryoo,et al.  Improvement in capacitive deionization function of activated carbon cloth by titania modification. , 2003, Water research.

[10]  T. D. Tran,et al.  Electrosorption of inorganic salts from aqueous solution using carbon aerogels. , 2002, Environmental science & technology.

[11]  Linda Zou,et al.  Using mesoporous carbon electrodes for brackish water desalination. , 2008, Water research.

[12]  Sotira Yiacoumi,et al.  Electrosorption of ions from aqueous solutions by carbon aerogel: An electrical double-layer model , 2001 .

[13]  Y. Oren,et al.  Capacitive deionization (CDI) for desalination and water treatment — past, present and future (a review) , 2008 .

[14]  C. F. Schutte,et al.  Capacitive Deionization Technology™: An alternative desalination solution , 2005 .

[15]  Yiwei Chen,et al.  Electrosorption behavior of cations with carbon nanotubes and carbon nanofibres composite film electrodes , 2009 .

[16]  Kang-Ho Lee,et al.  Capacitive deionization characteristics of nanostructured carbon aerogel electrodes synthesized via ambient drying , 2007 .

[17]  Hardcover,et al.  Carbon: Electrochemical and Physicochemical Properties , 1988 .

[18]  Pei Xu,et al.  Treatment of brackish produced water using carbon aerogel-based capacitive deionization technology. , 2008, Water research.

[19]  Chi-Woo Lee,et al.  Desalination performance of a carbon-based composite electrode , 2009 .