Effect of the chemical bond on the electrosorption and desorption of anions during capacitive deionization

Abstract

This paper is concerned with the effect of the chemical bond on the electrosorption and desorption of anions during capacitive deionization (CDI). An empirical equation developed firstly based on the experimental data in the electrosorption of Cl−. The empirical equation shows that the electrosorption capacity exhibits a logarithmic relationship with anode potential. Electrosorption of ReO4− and NO3− at different anode potentials were studied and the obtained data used to compare with empirical equation. The empirical equation provided results that were in good agreement with experimental data. According to parameters (A and b) of empirical equation, the chemical bond mainly affected adsorption mechanism and desorption performance. For Cl− with the weaker chemical bond, the main mechanism of electrosorption of Cl− is formation of electrical double layers and the desorption is easier, while for ReO4−, the main adsorption mechanism is chemical bonding and adsorbed anion basically fail to desorb at the equal conditions with Cl−. The revelation of all the CDI performance here would appear to be a useful tool for selection of more suitable electrodes materials to improve adsorption capacity and desorption efficiency of anions.