Kinetics of photocatalytic degradation of reactive dyes in a TiO2 slurry reactor

The textile industry consumes considerable amounts of water during the dyeing and finishing operations. Dyes are extensively used and hence wastewaters discharged in rivers or public sewage treatment plants are highly contaminated. In this work, a detailed investigation of the adsorption and photocatalytic degradation of the safira HEXL dye, an anionic azo dye of reactive class, is presented. H2O2 and UV light have a negligible effect when they are used on their own. The adsorption of dye on the semiconductor shows a strong dependence on the pH and follows a Langmuir adsorption model. The photodegradation kinetics is discussed in terms of the Langmuir-Hinshelwood model. The effect of pH, amount of photocatalyst, UV light intensity and hydrogen peroxide concentration is discussed. The relative photonic efficiency of the system is reported using phenol as a standard organic compound. (C) 2002 Elsevier Science B.V. All rights reserved.