Solar-light-assisted photocatalytic degradation of NBB dye on Zr-codoped Ag–ZnO catalyst

Abstract

Zr-codoped Ag–ZnO (Zr–Ag–ZnO) was successfully synthesized by the precipitation–decomposition method. The catalyst was characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectra (EDS), diffuse reflectance spectra, photoluminescence spectra, cyclic voltammetry, and Brunauer–Emmett–Teller (BET) surface area measurements. The photocatalytic activity of Zr–Ag–ZnO was investigated for the degradation of Naphthol Blue Black (NBB) in aqueous solution using solar light. Codoping shifted the absorbance of ZnO to the entire visible region. Zr–Ag–ZnO is found to be more efficient than Ag–ZnO, Zr–ZnO, commercial ZnO, prepared ZnO, TiO2-P25, and TiO2 (Merck) at pH 9 for mineralization of NBB under solar light. The influence of operational parameters such as the amount of photocatalyst, dye concentration, and initial pH on photomineralization of NBB has been analyzed. Mineralization of NBB was confirmed by chemical oxygen demand (COD) measurements. A mechanism is proposed for the degradation of NBB under solar light. The catalyst is found to be reusable.