Visible-light-induced photocatalytic degradation of azodyes in aqueous AgI/TiO2 dispersion

Agl/TiO2 was prepared by the deposition-precipitation method and was found to be a novel visible light driven photocatalyst. The catalyst showed high efficiency for the degradation of the nonbiodegradable azodyes reactive red K-2G, reactive brilliant red X-3B, reactive red K-2BP, and reactive yellow KD-3G under visible light irradiation (lambda > 420 nm). The catalyst's activity was maintained effectively after successive cyclic experiments under visible irradiation without the destruction of Agl. On the basis of the characterization of X-ray diffraction, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, the structure of Agl loaded on TiO2 did not significantly change before and after reaction. K-2G was completely decolorized and partly mineralized. The main intermediates are the small organic acids besides CO2 and cyanuric acid, which is photostable. The center dot OH is the main active oxygen species in the photocatalytic reaction by the studies of electron spin resonance and the effect of radical scavengers