Visible-Light-Induced Photocatalytic Degradation of Azodyes in Aqueous AgI/TiO2 Dispersion

Abstract

AgI/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 (λ > 420 nm). The catalyst's activity was maintained effectively after successive cyclic experiments under visible irradiation without the destruction of AgI. On the basis of the characterization of X-ray diffraction, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, the structure of AgI 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 ^•OH is the main active oxygen species in the photocatalytic reaction by the studies of electron spin resonance and the effect of radical scavengers.