Electrochemical Oxidation of Aqueous Phenol Wastes Using Active and Nonactive Electrodes

Abstract

The electrochemical oxidation of acidic aqueous phenol wastes has been studied using boron-doped diamond thin-film (BDD) and AISI 304 stainless steel (SS) electrodes. A voltammetric study shows marked differences in the electrochemical behavior of these two electrodes. The surface of the SS electrodes undergoes significant changes when this material is used as the anode in the treatment of aqueous wastes, even in the potential region of electrolyte stability. These changes have important effects on the waste treatment process. Conversely, the BDD electrode does not undergo any appreciable change during the electrochemical oxidation of the wastes. An electrolysis study highlighted significant differences between the behavior of the two electrodes. First, the oxidation performed using a BDD electrode leads to the rapid sequential formation of aromatic compounds (hydroquinone, benzoquinone), carboxylic acids (maleic, fumaric, and oxalic), and carbon dioxide. The oxidation performed using SS electrodes, on the other hand, involves a slower sequential formation of the 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 resulting from the electrocoagulation of organic matter with iron dissolved from the electrode. © 2002 The Electrochemical Society. All rights reserved.