title: Highly efficient, solar active, and reusable photocatalyst: Zr-loaded Ag-ZnO for Reactive Red 120 dye degradation with synergistic effect and dye-sensitized mechanism.
abstract: The different wt % of Zr-codoped Ag-ZnO catalysts were prepared by the simple precipitation-thermal decomposition method and used for  degradation of anionic azo dye Reactive Red 120 (RR 120) under natural sunlight. Highly efficient 4 wt % of Zr-codoped Ag-ZnO was characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM) images, field emission scanning electron microscope (FE-SEM) images, energy-dispersive spectra (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL), cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), and BET surface area measurements. Metal codopants increase the absorbance of ZnO to the entire visible region. XRD and XPS reveal that Ag is in the form of Ag(0) and Zr in the form of Zr(4+). The photocatalytic activity of 4 wt % Zr-codoped Ag-ZnO was compared with other single-metal-doped, undoped, and commercial catalysts. The quantum yields of all  processes were determined and analyzed. Zr-Ag-ZnO was found to be more efficient than Ag-ZnO, Zr-ZnO, commercial ZnO, prepared ZnO, TiO(2)-P25, and TiO(2) at neutral pH for  mineralization of RR 120 under solar light. To the best of our knowledge, this is the first report on the synthesis of Zr-codoped Ag-ZnO and its use in the degradation of RR 120 dye under natural sunlight illuminatioin. The influences of operational parameters such as the amount of photocatalyst, dye concentration, and initial pH on photomineralization of RR 120 have been analyzed. Mineralization of RR 120 has been confirmed by chemical oxygen demand (COD) measurements. A dual mechanism has been proposed for the higher efficiency of Zr-Ag-ZnO at neutral pH under solar light. This catalyst is found to be reusable.
authors.affiliation: Photocatalysis Laboratory, Department of Chemistry, Annamalai University, Annamalainagar, Tamil Nadu, India.
authors.forename: B
authors.initials: B
authors.lastname: Subash
authors.forename: B
authors.initials: B
authors.lastname: Krishnakumar
authors.forename: M
authors.initials: M
authors.lastname: Swaminathan
authors.forename: M
authors.initials: M
authors.lastname: Shanthi
mesh_terms: D002384:Catalysis; D010100:Oxygen / Q000032:analysis; D010316:Particle Size; D055668:Photochemical Processes; D012834:Silver / Q000737:chemistry*; D013499:Surface Properties; D014227:Triazines / Q000737:chemistry*; D014466:Ultraviolet Rays; D015034:Zinc Oxide / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D014227:Triazines; D012834:Silver; C042516:reactive red 120 dye; D015040:Zirconium; D010100:Oxygen; D015034:Zinc Oxide