Zinc oxide-catalyzed UV-photodegradation of cyhalothrin: A kinetic analysis

Abstract

In this study, we present kinetic studies of the photodegradation of cyhalothrin (CyH) under ultraviolet (UV) irradiation and the photocatalytic activity of zinc oxide (ZnO) in UV-assisted photodegradation. CyH in an acetone solvent was periodically exposed to UV254 nm radiation light with a surface power density of 48 W/cm2. The photodegradation experiments were conducted by acquiring periodic wavelength-scan spectroscopic data using a double beam ultraviolet-visible (UV-vis) spectrophotometer and plotting the real-time absorbance data to monitor the reaction coordinate. Under our optimized conditions at room temperature of 26.5 °C, atmospheric pressure of 76.6 mmHg, CyH (5.0 ppm) in the 70% acetone solvent with pH = 6.8 and dose of ZnO (25 ppm) exhibited typical photodegradation efficiencies between 81.9 and 90.3 % within the first 1,200 seconds of UV irradiation. Spectroscopic data showed that the ZnO solution significantly elevated the UV-assisted photodegradation rate of CyH by about 7.03 - 7.18 times more than that of UV-only-mediated CyH photodegradation. The result confirmed and characterized the photocatalytic activity of ZnO. Under the optimized measurement conditions, the rate of the ZnO-catalyzed photodegradation of CyH was found to follow the first-order rate law (RSq. = 0.999)