Electro-oxidation of chlorophenols on powdered carbon electrodes of different porosity

Abstract

Activated carbons with large and medium-sized S BET, carbon blacks with different surface areas as well as graphite and heat-treated carbon of extremely low porosity were used in this study. Cyclic voltammograms were recorded for these materials in neutral electrolyte (0.1 M Na2SO4) solutions containing various chlorophenols (CPs; 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol) as depolarizers. The changes in the FTIR spectra of the electrode materials caused by the adsorption and/or coupling of CPs (and/or their degradation products) were recorded. HPLC was used for analyzing the concentration of CPs and their degradation products. The dependence of the electrochemical behavior of CPs with various chlorine contents on the character of carbon materials is discussed. The possible mechanism of the initial stages of CP degradation by electro-oxidation/reduction depends on the kind of electrode material. Since different carbons vary in their electrochemical behavior and in their voltammetric response to the presence of different CPs, the application of the method for selecting electrode materials better suited to removing organochlorine impurities from ground-water seems feasible. The efficiency of the process depends closely on the kind of carbon and on the tendency for its surface to become covered by a polymeric (conducting or non-conducting) film of electro-degradation products.