Photocatalytic degradation of diazinon by illuminated WO₃ nanopowder

Abstract

In this study, photocatalytic degradation of diazinon as a model phosphorothioate insecticide by tungsten oxide nanopowder under UV irradiation was investigated. Effect of operational parameters including WO₃ dosage, pH, initial diazinon concentration, and organic compounds (humic acid, oxalic acid, phenol, ethylenediaminetetraacetic acid (EDTA)) on the photocatalytic degradation of diazinon was studied. Degradation efficiency of diazinon by WO₃/UV process was more effective than WO₃-alone and UV-alone. As the nanocatalyst dosage increased, the photocatalytic degradation of the diazinon decreased. Removal efficiency was decreased by increasing pH and initial diazinon concentration. The reaction rate constant (k_obs) was decreased from 0.1233 to 0.0001/min, and the value of electrical energy per order (E_Eo) was increased from 38.93 to 48,000 (kWh/m³) with increasing initial diazinon concentration from 5 to 50 mg/L, respectively. The photocatalytic degradation of diazinon was increased in the presence of oxalic acid and EDTA, while different trend was observed in the presence of phenol and humic acid. Proper photocatalytic activity was observed even after five successive cycles. Finally, UV/WO₃ is identified as a promising technique for the removal of diazinon with high efficiency in a short reaction time.

Keywords:

• Tungsten oxide
• Diazinon
• Photocatalysis
• Kinetics

Acknowledgment

The authors thank the Guilan and Iran Universities of Medical Sciences, Iran for all of the support provided.