The photocatalytic degradation of Reactive Red 180 (RR180), a mono-azo textile dye, has been investigated using aqueous suspensions of titanium dioxide (TiO2) under visible light irradiation. The photocatalytic degradation is monitored by measuring the decolorization rate and the total organic carbon (TOC) content reduction during the course of the reaction. The effect of catalyst concentration, substrate concentration, pH of the solution and addition of electron acceptors, such as hydrogen peroxide (H2O2), potassium peroxodisulfate (K2S2O8) and potassium peroxomonosulfate (PMS or ozone), on the photocatalytic degradation of RR180 in the presence of colloidal titanium dioxide is also studied. The photocatalytic degradation rate is found to be depending on the ratio of TiO2 to dye. Addition of oxone in the TiO2-RR180 system increases the degradation rate by about 10 fold and is found to be promising for the degradation of Reactive Red 180 when compared with other electron acceptors. About 80% of the dye is mineralized in 5 h through visible light photocatalytic degradation in the presence of TiO2 and oxone. (C) 2011 Elsevier B.V. All rights reserved.