Role of adsorption in the photodegradation of a dye, acid-blue 92

Abstract

The effect of adsorption onto the TiO2 particle surface, on the photodegradation rate of a dye acid-blue 92, was investigated. Overall adsorption rate was estimated by using a differential bed reactor with TiO2 particles and without UV radiation, while photodegradation rate was determined in a TiO2 immobilised photoreactor with UV radiation. Overall adsorption rate of the dye acid-blue 92 was higher in a strong acidic region at pH 3 than in a weak acidic region at pH 6 and was the lowest at pH 7 and 8. The photodegradation rate of the dye acid-blue 92 with respect to initial concentration could be described as an apparent first order kinetics, where the rate constants (K) were estimated as 0.012, 0.010, and 0.008 min(-1) at pH 3, 5, and 7, respectively. The change of pH affected both photodegradation and adsorption rates of the dye acid-blue 92 and the close relationship between overall adsorption and photodegradation rates could be observed dependently on the pH variation.