Electrochemical oxidation of aqueous phenol wastes using active and non-active electrodes

The electrochemical oxidation of acid phenol aqueous wastes is studied in this work using boron doped diamond thin film (BDD) and AISI 304 stainless steel (SS) electrodes. A voltammometric study shows big differences in the electrochemical behaviour of both electrodes. The surface of the SS electrodes undergoes important changes when this material is used as anode in the treatment of aqueous wastes, even in the potential region of electrolyte stability. These changes have important effects on the waste treatment. Conversely the BDD electrode do not register any appreciable change during the electrochemical oxidation of the wastes. An electrolysis study shows too important differences between the behaviour of both electrodes. Thus, the oxidation performed by a BDD electrode deals to the quick sequential formation of aromatic compounds (hydroquinone, benzoquinone), carboxylic acids (maleic, fumaric and oxalic) and carbon dioxide. The oxidation performed by SS electrodes deals to a more slower sequential formation of same compounds, indicating a lower energetic efficiency of these electrodes in the destruction of the organic matter, and to the formation of some insoluble compounds formed by the electrocoagulation of organic matter with iron dissolved from the electrode.