Photoassisted Electrochemical Incineration of Selected Organic Compounds

Abstract

The decrease in chemical oxygen demand (COD) of mildly acidic (pH 3.5) aqueous solutions of phenol, aniline, -propanol, and acetic acid was observed to be significantly larger at -coated Pt electrodes (“”) in comparison to bare Pt electrodes in a flow-through reactor. Furthermore, the rate of production during electrolysis of phenol solutions at electrodes also was determined to be significantly larger when these electrode surfaces were illuminated by a 14 W UV lamp (254 nm). The total amount of produced over a 4 h electrolysis period at an illuminated electrode in a flow-through cell was equal to 90% of the theoretical amount, corresponding to stoichiometric conversion of the phenol to Elemental analysis of the films demonstrated that they were doped slightly with iron, presumably in the Fe(III) state, i.e., The source of Fe(III) was concluded to be the stainless steel used in construction of the flow-through electrolysis vessel. It is speculated that the Fe(III) sites in the surfaces of the films can function as Lewis acid sites for adsorption of reactant molecules via nonbonded electrons as an initial step in the anodic degradation mechanisms. The advantage of preadsorption of reactant molecules is thought to be the result of longer residence times for these molecules within the applied electric field at the electrode-solution interfacial region. The observed effect of UV illumination is speculated to be associated with absorption of the photons within the surface of the films. © 2001 The Electrochemical Society. All rights reserved.