H2O2/UV-C and Fe2+/H2O2/UV-C versus TiO2/UV-A treatment for reactive dye wastewater

This study investigated the advanced oxidation of commonly used reactive dyestuffs in exhausted dye-bath effluents in homogeneous (H2O2/UV-C and photo-Fenton) and heterogeneous (TiO2/UV-A) media. Photocatalytic treatment efficiencies of two different TiO2 powders (PC 500 and Mikroanatas) and the platinized Degussa P25 were compared with that of the more well-known Degussa P25 in varying pH media. Treatment performance was strongly affected by the initial H2O2 concentration for H2O2/UV-C and photo-Fenton oxidation systems, whereas for the TiO2/UV-A process only PC 500 TiO2 powder, an anatase crystal phase of the semiconductor, exhibited a significantly pH-dependent reaction efficiency. The decolorization rate followed the order of Fenton/UV-C > Pt-P25/UV-A > Mikroanatas/UV-A > P25/UV-A > PC 500/UV-A > H2O2/UV-C, whereas the decreasing order for total organic carbon reduction was Fenton/UV-C > H2O2/UV-C > Mikroanatas/UV-A > Pt-P25/UV-A > P25/UV-A > PC 500/UV-A for the studied reaction conditions. Removal of optical density at 254-nm wavelength ranged between 75 and 96%.