Response Surface Methodology Modelling of Diazinon Photodegradation Using Tio2-zno

A semiconductor composite photocatalyst, TiO2-ZnO, was synthesized by precipitating ZnO on the surface of commercial TiO2 (aeroxide P25), and used for the photodegradation of diazinon in a 12 W UVC batch photoreactor. Scanning electron microscopy (SEM) investigation revealed a plausible hybridization of TiO2 and ZnO in the composite. Ultraviolet visible (UV-Vis) spectroscopy confirmed a red shift in the composite resulting in lower energy requirement. Central composite design (CCD) was used to evaluate and optimize the effect of operational parameters such as initial pH, initial concentration and composite composition by ZnO, on diazinon removal. Analysis of variance (ANOVA), with high coefficients of correlation (R2 = 0.9946 and adjusted R2 = 0.9877), confirmed a good agreement between experimental and predicted values. Response surface methodology (RSM) was used to obtain 3D surface plots, which revealed that all the operational parameters investigated are significant in the degradation process. For the optimized conditions, maximum diazinon removal obtained was 82%, at initial pH and concentration of 5.28 and 10 ppm, respectively, and ZnO composite composition by weight of 25%.