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%.
Key words — Diazinon, modelling, optimization, semiconductor composite, titanium dioxide, zinc oxide.