The sulfate modified titania (TiO2-SO42-) was prepared by sol-gel method using tetraisopropyl orthotitanate with sulfuric acid and characterized by XRD, FT-IR, BET and SEM techniques. TiO2 is mesoporous in nature but sulfate doping inhibits the phase transformation and enhances the thermal stability and photocatalytic activity. Sulfate modification using H2SO4 reduces the crystal size from 34.7 to 11.6 nm and increases the acidity of TiO2. Sulfated titania is found to be more efficient than TiO2-P25 in the degradation of Reactive Orange 4 (RO 4). The effects of different parameters such as pH of the solution, amount of catalyst, initial concentration of dye and the influence of cations, anions and oxidants on photodegradation of RO 4 were analyzed. (C) 2010 Elsevier B.V. All rights reserved.