In this work the synthesis of Au-doped and Pt-doped TiO2 nanoparticles employing sol-gel methodology. The doping procedures based on chemical reduction and UV photodeposition. The morphology, composition, particle size and specific surface area of these synthesized nanoparticles have been characterized using several instrumental techniques namely, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDXS), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and N2-adsorption Brunauer–Emmett–Teller (BET) methodology. Au impregnated (2%) nano anatase TiO2 powder and Pt-impregnated (4%) nano anatase TiO2 were examined in photo decolourization of Orange G as dye environmental pollutant under visible light illumination and optimum operational conditions. The effects of some experimental variables for the photodegradation of the OG by Au-TiO2 and Pt-TiO2 have been investigated including, initial solution pH, initial dye concentration, Au-TiO2 and Pt-TiO2 loading amounts, and visible light intensity. At optimum operational conditions for OG including pH = 3, 50 mg Au-TiO2 loading, and 10 mg/l OG, the value of the apparent rate constant, kapp , obtained has been 0.0123 min-1 and the half life of the process, accordingly is equal to 56 min. Whereas, for Pt-TiO2 implying pH = 3, 40 mg Pt-TiO2 loading, and 10 mg/l OG, the value The main process activation thermodynamic parameters namely, Gibbs energy, enthalpy and entropy were also deduced following the computation of photolysis activation energy employing the well known Arrhenius relation.Employment of Au-TiO2 revealed lower rate constant and longer half life for OG degradation, while Pt-TiO2 exhibited higher rate constant and shorter half life, i.e; better photocatalytic activity of Pt/TiO2 over Au/TiO2.
