Photodecolourization of ponceau 4R by heterogeneous photocatalysis

The photodecolourization of ponceau 4R dye has been carried out using a combination of TiO2 and UV irradiation (λ = 254 nm) at a pH of 6. Dye decolourization was also assessed by adding low concentrations of inorganic oxidants, such as Na2S2O8 (5 × 10−4 to 1.8 × 10−2 M) and NaIO4 (1 × 10−4 to 5 × 10−4 M) to TiO2 in the presence of UV radiation. It was observed that dye decolourization was enhanced using UV/TiO2/Na2S2O8 and UV/TiO2/NaIO4 catalytic systems over UV/TiO2 alone. First-order kinetics adequately described the disappearance of the dye. Reaction rate orders with respect to the oxidant species were 0.46, 0.58, and 1.55 for, respectively, TiO2, Na2S2O8, and NaIO4. The most effective catalytic system for dye decolourization was found to be UV/TiO2/NaIO4. The influence of dye concentration varying from 4 × 10−5 to 1 × 10−4 M on the degradation rate was studied. It can be seen that the degradation rate increases with the increase in dye concentration.