Optimized Photocatalytic Degradation of 4- Nitrophenol over N,S-codoped ZnO Photocatalyst

In this study, a well defined photoactive N,Scodoped ZnO catalyst was synthesized through by a lowtemperature alkali co-precipitation of zinc acetate dihydrate precursor in presence of ammonium sulfate as dopants’ source. The catalyst was characterized by Xray diffraction (XRD), scanning electronmicroscopy (SEM), energy dispersive x-ray (EDX), UV-visible analysis and FT-IR spectroscopy. The diffraction peaks of undoped and N,S-codoped lines materials are in accordance with the wurtzite hexagonal phase of ZnO. The insertion of the dopants (S and N) and the vigorous agitation during the catalyst preparation caused a decrease in the crystallites size. Visible light photocatalytic studies were carried out using 4- nitrophenol (4-NP) as pollutant. The effect of experimental variables for the photocatalytic degradation such as pH, initial 4-NP concentration, temperature and catalyst loading was optimized based on central composite design (CCD) and response surface methodology. The results indicated that photocatalytic activity of N,S-codoped ZnO (99.3%) was better than undoped ZnO (82%), because the band gap of doped was lower than undoped ZnO photocatalyst which is herein attributed to shift in the band gap caused by the dopants.