Mass-Transfer and Kinetic Studies during the Photocatalytic Degradation of an Azo Dye on Optically Transparent Electrode Thin Film

Photocatalysis is an efficient method to eliminate azo dyes. We have studied the various parameters that affect the kinetics of the degradation process for an azo dye in an aquatic flow system using a novel batch continuous-loop flow reactor with TiO 2 colloids immobilized on a flat substrate. A detailed study of physical parameters including light intensity, flow rate, stirring, catalyst loading, dye concentration, and temperature has been performed to obtain the reaction kinetics independent of mass-transport limitations. The kinetic parameters of the degradation process, viz., rate constant, order of reaction, and activation energy, have been obtained first using a power-law rate expression and then using an expression based on a Langmuir−Hinshelwood mechanism. The kinetic parameters for a model consistent with the reaction pathway have been estimated. Metal nanoparticles have been reported to be useful for enhancing the photocatalytic activity of semiconductors. We have studied the effect of metal nanoparticles on the photocatalytic activity of TiO 2 under the optimized conditions of a flow reactor to determine the role of metal nanoparticles in the photocatalytic degradation of AO7.