Decolorization and aromatic ring degradation kinetics of Direct Red 80 by UV oxidation in the presence of hydrogen peroxide utilizing TiO2 as a photocatalyst

Textile industry consumes considerable amounts of water during various processes such as dyeing. The existence of color and aromatic rings in the form of aromatic amines in textile wastewater is a very important problem. In this paper, photocatalytic decolorization and aromatic ring degradation of Direct Red 80 in a fixed bed photocatalytic reactor, utilizing a very simple analytical method, direct UV-vis spectrophotometric detection, has been investigated. Photocatalytic decolorization and aromatic ring degradation processes performed using a 5 l solution containing Direct Red 80. The initial concentration of Direct Red 80 was 50 mg l−1. The radiation source was two 15 W UV-C lamps. A batch mode immersion photocatalytic reactor was utilized. The effect of variables such as pH and H2O2 concentration were studied. Bench scale simulated colored textile wastewater was completely decolorized in a relatively short time after UV irradiation with a low concentration of hydrogen peroxide. The lack of any absorbance in the UV-vis spectra was indicative of the complete aromatic ring degradation. Kinetics analysis indicates that the dye photocatalytic decolorization rates can usually be approximated pseudo-first-order model. UV/TiO2/H2O2 process proved capable of the complete degradation of the Direct Red 80.