Study of photocatalytic oxidation of indigo carmine dye on Mn-supported TiO2

A detailed comparative investigation on the discoloration (adsorption) and mineralization (in the presence of UV irradiation) of indigo carmine (IC) dye over four photocatalysts TiO2-D (from Degussa), TiO2-SG (prepared with a sol–gel method), Mn/TiO2-imp (prepared with an impregnation method) and Mn/TiO2-SG (prepared with a sol–gel method) is presented. The experimental results show that Mn/TiO2-imp gives the highest photocatalytic activity. Whoever, the influence of pH, catalyst amount and time on the decolorization rate of IC on Mn/TiO2-imp was thoroughly discussed and correlated with ZPC of MnOx species, various exposed species of MnOx and surface properties. XRD, FT-IR and N2 adsorption measurements were used as characterization techniques over the calcined catalysts at 550 °C. Electric conductivity measurements by applying zeta potential technique provide an insight into the electric static situation of the particles at a given pH.