Enhanced photocatalytic removal of phenazopyridine by using silver-impregnated SiO-TiO nanoparticles: optimization of synthesis variables.

Silver-impregnated silicon oxide/titanium oxide nanoparticles (Ag/SiO-TiO) were prepared via impregnation method. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and UV-Vis diffuse reflectance spectroscopy techniques were used for the characterization of prepared nanoparticles. The effects of synthesis variables such as nanoporous SiO content, Ag content, impregnation pH, and calcination temperature were studied in the photocatalytic activity of prepared nanoparticles in the removal of phenazopyridine as a model drug contaminant. Response surface methodology as a statistical technique was employed for modeling and optimizing synthesis variables. Results showed that the maximum removal efficiency (97.14 %) was achieved for Ag/SiO-TiO nanoparticles at the optimized preparation conditions: SiO content of 34.68 wt%, Ag content of 2.36 wt%, impregnation pH of 5.1, and calcination temperature of 439 °C, whereas at the same conditions, using TiO, SiO-TiO, and Ag-TiO samples lead to 50.14, 60.37, and 71.45 % removal efficiency, respectively. Coupling SiO with large surface area significantly enhanced adsorption of drug molecules, and also impregnation of Ag onto the hybrid system by its ability to trap electrons, provided a synergistic effect in the enhancement of the TiO nanoparticles photocatalytic activity. [ABSTRACT FROM AUTHOR]