Determination of overall kinetic constants for mediated electrochemical oxidation of phenol from CO2 measurements

Abstract

Mediated electrochemical oxidation is the latest achievement in environmental electrochemistry for the complete oxidation of organic pollutants. Transition or inner transition elements in an acid medium are usually employed as the mediator-electrolyte combination. The organic pollutants upon oxidation are completely converted to carbon dioxide and water. Since the oxidizing ability of the medium is so vigorous, the changes in the reactant concentrations or intermediates formed are usually difficult to analyze, but the product formed (CO2) can be measured and quantified in most of the cases. Therefore, in MEO reactions the kinetics can be followed either by monitoring the oxidant concentration changes or by measuring the product concentrations. In real applications the oxidant is regenerated continuously in situ and, hence, the oxidant concentration is maintained throughout the system. Therefore, in continuous organic feeding reactions, the product CO2 could be monitored and kinetics could be followed. We report in this paper a simple procedure for the calculation of the overall kinetic constants for the destruction of phenol from CO2 measurements. The procedure is based on the summation of the difference between the total amounts of organic added to the system and reacted to obtain CO2 evolution patterns. The CO2 patterns were then fitted with the experimental results to obtain the overall kinetic constants. Thermodynamic parameters have been obtained for phenol destruction from the overall kinetic constants.