Photocatalytic degradation of reactive orange 16 dye over Au-doped TiO<SUB align=right>2 in aqueous suspension

Abstract

The effect of nanosized Au deposits on TiO2 particles for the photocatalytic degradation of reactive orange 16 dye (RO 16) as model compound was investigated. The deposition of Au on TiO2 was carried out by deposition-precipitation (DP). The catalysts were characterised by XRD, TEM, and XPS analyses. The photocatalytic experiments were carried out under a radiation source of low-pressure mercury vapour lamp (6 W) emitting ultraviolet light with maximum intensity at 253.7 nm. The Au deposits significantly enhanced the degradation rate of the dye. The significant enhancement of the Au/TiO2 photocatalyst can be ascribed to the trapping of photogenerated electrons by nano-sized gold particles, which subsequently increase the lifetime of the photogenerated hole for oxidation process and also increased light absorption by crystalline defects. The catalytic activity was found to be dependent on the metal content on TiO2 and showed a maximum at 2 wt% Au. The amount of catalyst was optimised as 2.5 g/L. The photocatalytic activity was strongly dependent on the initial pH of the suspension; pH values in the range 5-10 showed better activity, whereas highly acidic and basic suspensions resulted in a considerable decrease in the activity.