Application of electrochemical impedance spectroscopy to solvent extraction of metallic ions

Abstract

An electrochemical impedance spectroscopy (EIS) was applied to the investigation of the solvent extraction mechanism of metallic ions across a water/1,2-dichloroethane interface. In the electrochemical measurement, the transfer of a metallic ion–chelating reagent complex across the interface can be detected as the electrochemical response. Electrochemical impedance showed a capacitive semi-circle and an apparent Warburg impedance, indicating that the diffusion process contributed to the total transfer rate. A theoretical expression which represents the electrochemical impedance for solvent extraction of a metallic ion–chelating reagent complex was derived, and numerical simulations were performed. The rate constants obtained by the simulation were compared with the extraction constant.