Photocatalytic decolourisation and degradation of Reactive Orange 4 by TiO2-UV process

The photocatalytic decolourisation and degradation of an azo dye Reactive Orange 4 (RO4) in aqueous solution with TiO2-P25 (Degussa) as photocatalyst in slurry form has been carried out using UV-A light (365 nm). There is a significant difference in adsorption of dye on TiO2 surface with the change in the solution pH. The effect of various parameters such as catalyst loading, pH and initial concentration of the dye on decolourisation and degradation have been determined. The dye is decolourised in 80 min and completely degraded in 180 min under optimum conditions. The degradation was strongly enhanced in the presence of electron acceptors such as H2O2, (NH4)2S2O8 and KBrO3. The photodecolourisation and degradation kinetics are discussed in terms of Langmuir–Hinshelwood kinetic model. The degradation intermediates were analysed by GC–MS technique.