STUDY OF A LABORATORY FILTER-PRESS CELL BY IMPEDANCE SPECTROSCOPY

Impedance spectroscopy is often used in the laboratory to study the kinetics of electrochemical systems with rotating disc electrode devices. A possible application of this method may be the control of electrochemical processes because it allows analysis of a system over a large frequency range, measurement of reaction or cell parameters like the electrolyte ohmic drop and the interfacial capacitances, and characterization of the kinetics of electron transfer and the hydrodynamic behaviour of the electrolyte. In this work the feasibility of studying the kinetics of an electrochemical system by voltammetry and impedance spectroscopy in a laboratory filter-press cell is described, under conditions approximating those of a subsequent industrial plant. Using a model system such as Fe III complex reduction in an aqueous solution of KOH on a titanium electrode, the hydrodynamics of the cell was studied from the low frequency part of the impedance diagram, corresponding to the diffusion-convection impedance. The results were described as a first approximation by the Nernst model and were consistent with the description of the system under steady-state conditions.