Effect of Oxygen Concentration on the Kinetics of the Photocatalytic Degradation of Dichloroacetic Acid

C. ZALAZAR, C. A. MARTÍN Y A. E. CASSANO

Barcelona, España

Congreso; SPEA3 3rd European Meeting on Solar Chemistry and Photocatalysis: Environmental Applications; 2004

The effect of oxygen concentration on the photocatalytic oxidation of low concentration, aqueous solutions of dichloroacetic acid (DCA) - a typical by product of chlorine disinfection - was studied employing titanium dioxide and UV radiation. The study aims at the development of an intrinsic and complete reaction kinetics (apt for scaling-up purposes) that will consider also the oxygen demand as one of the design variables. This problem becomes particularly important for liquids having a very high COD. This objective can be achieved only if the laboratory reactor is precisely modeled in order to use the complete mathematical description of de process in combination with a multi parameter estimation to evaluate the reaction kinetic constants. Using the mass action law and the micro steady state approximation, a kinetic model was developed starting from a complete reaction sequence based on the direct hole attack of DCA and the participation of oxygen as the main electron acceptor. The obtained representation gives reaction rates for the DCA and oxygen disappearance as well as chloride ion formation. The model includes the local rate of photon absorption and requires only a maximum of three kinetic parameters. In a previous work the reaction kinetics of the same reaction, at different levels of constant oxygen concentration, was studied and the results are consistent with the ones presented here.constant oxygen concentration, was studied and the results are consistent with the ones presented here.