Environmental Photochemistry:  Quantitative Adsorption and FTIR Studies during the TiO₂-Photocatalyzed Degradation of Orange II

Abstract

The degradation rate of Orange II, taken as a model for recalcitrant azo-dyes, was observed to be a function of the type of TiO 2 semiconductor used during the process. The surface parameters of the titania material used seem to be a controlling factor in the photosensitized charge-transfer process. The dye abatement was monitored by diffuse reflectance FTIR. When H 2 O 2 was initially added as an oxidant to the photodegradation process, the rate of dye removal from soluton was accelerated significantly. The pore and particle size distribution of the anatase, mixed anatase−rutile (Degussa P-25), and rutile was quantified by gas adsorption and mercury porosimetry. The degradation on rutile and anatase was observed to follow pseudo-first-order kinetics during the initial stages of the reaction. The photodegradation of Orange II was seen to proceed more readily in the case of anatase than in that of rutile. The rate was seen to increase with the surface area and the monolayer volume of the titania variety used.