Sonochemical synthesis of Au-TiO2 nanoparticles for the sonophotocatalytic degradation of organic pollutants in aqueous environment.

Au-TiO2 photocatalysts were sonochemically prepared by three different procedures and their photocatalytic and sonophotocatalytic efficiencies were evaluated by studying the degradation of a representative organic pollutant, nonylphenol ethoxylate (NPE) surfactant in aqueous solutions. In the first procedure, Au-TiO2 nanoparticles were prepared by depositing sonochemically synthesized gold nanoparticles on Degussa P25 TiO2 by stirring in the absence of an ultrasonic field. In the second procedure, Au nanoparticles were sonochemically synthesized and simultaneously deposited on Degussa P25 TiO2 particles. In the third procedure, Au-TiO2 nanoparticles were sonochemically synthesized by the simultaneous irradiation of an aqueous solution containing AuCl4- and titanium tetraisopropoxide. The prepared nanoparticles were characterized by UV-vis spectroscopy and transmission electron microscopy (TEM). The catalytic activities of these nanomaterials were compared for the degradation of a polydisperse nonylphenol ethoxylate, Teric GN9 by photocatalysis and sonophotocatalysis under visible light/high frequency ultrasound irradiation. The catalysts did not show a synergetic effect towards the sonophotocatalytic degradation of Teric GN9. This might be due to the interference of the degradation products generated during the simultaneous irradiation by light and ultrasound.