Synthesis, characterization and daylight active photocatalyst with antiphotocorrosive property for detoxification of azo dyes

Abstract

Abstract Utilization of solar energy is an energy efficient process for dye wastewater treatment. Photocatalytic degradation of toxic azo dyes was carried out using modified semiconductors under direct sun light. Concerning this, the different wt% of CdS loaded Ag–ZnO catalysts were prepared by the simple precipitation – thermal decomposition method and used for degradation studies. Cadmium sulfide (CdS) is a kind of semiconductor with fine band gap of 2.4 eV, and its valence electron can be effortlessly evoked to conduction band under solar or visible light illuminations. Among the different CdS prepared catalysts, highly efficient 2 wt% of CdS loaded Ag–ZnO was characterized by different characterization techniques. Metal sulfide loading increases the absorbance of ZnO into the entire visible region. XPS reveals that the presence of metallic silver in the catalyst. The photocatalytic activity of 2 wt% CdS loaded Ag–ZnO was compared with single metal doped, undoped, and other commercial catalysts, especially Degussa P25, a standard bench mark photocatalyst. The photodegradation of RR 120, RO 4, and RY 84 had been analyzed in detail. Mineralization of these dyes has been confirmed by chemical oxygen demand (COD) measurements. A dual mechanism has been proposed for the higher efficiency of CdS–Ag–ZnO at neutral pH under solar light. Antiphotocorrosive study reveals that bare ZnO suffers more dissolution by photocorrosion than our prepared photocatalyst CdS–Ag–ZnO. This catalyst is found to be more stable and reusable.