Synthesis, Characterization and Immobilization of ZnO Nanosheets on Scallop Shell for Photocatalytic Degradation of an Insecticide

Photocatalytic degradation of diazinon as a model phosphorothioate insecticide by immobilized ZnO nanosheets on scallop shell under UV irradiation was investigated. A convenient and low-cost co-precipitation method was utilized for stabilization of ZnO nanosheets on scallop shell. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques were used for characterization of the prepared photocatalyst. Degradation efficiency of diazinon by immobilized ZnO was more effective than suspension form in similar conditions. The effect of operational parameters including nanocatalyst dosage, pH and initial diazinon concentration on the UV/ZnO-scallop process was studied. As the nanocatalyst dosage increased, the photocatalytic degradation of the diazinon enhanced up to the desired amount of 0.5 g/L. Neutral pH was selected as optimal one due to photodecomposition of ZnO in acidic and basic mediums. Photocatalytic degradation declined with increasing of diazinon concentration due to its inner filtration effect and less generation of active radicals. Finally, the Langmuir-Hinshelwood model was applied to explain the kinetic of process and proper photocatalytic activity was observed even after five successive cycles.