Photodegradation of NPE-10 surfactant by Au-doped nano-TiO2

Nonionic surfactants, such as nonylphenyl poly(oxyethylene)ethers (NPE-10), were widely used in domestic and industrial products. The biodegradability of this kind of surfactants is one of the important constraints for their applications. The biodegradation of NPE-10 often leads to the formation of more persistent and even more toxic intermediates resulting in environmental problems. Efforts have been made to develop new waste treatment techniques including photodegradation. egration for NPE-10 has been carried out in air-equilibrated Au/TiO2 suspensions. The Au/TiO2 powders were prepared by sol–gel route at ambient temperature using Ti(OC4H9)4 and HAuCl4. The as-prepared samples were analyzed by XRD, BET, XPS and UV–visible absorption spectra techniques. The results suggest that the conformation of Au in the TiO2 composite greatly depended on concentration of HAuCl4 during the preparation and the temperature of calcination. The doped Au may take place Ti4+ in the lattices of TiO2 as Au3+ or exist at surface of TiO2 particles as atoms. The former may contribute to light adsorption range from 480 to 650 nm and may produce more O vacancies; the latter may become the acceptor of photoinduced e− leading to a decrease of e− to h+ recombination. The preparation parameters were optimized by means of NPE-10 degradation. The optimized catalyst was obtained at Au/Ti molar ratio of 0.005 and at 500 °C for calcinations. The degradation rate of NPE-10 could be up to 91.8% after being irradiated 4 h in sunlight compared to 66% for the rate by TiO2–P-25% and 52.6% for the rate by no-doping TiO2.