The degradation of malathion was investigated under various conditions, including ultrasound (US) irradiation, ultraviolet (UV) irradiation, and the combination of US/UV, UV/ZnO, UV/H2O2, and US/UV/ZnO/H2O2. In addition, the effect of the operational parameters, such as the initial concentration of the catalyst, the initial malathion concentration, the initial salt concentration (NaHCO3 and Na2SO4), and pH, were studied. Analyses were performed by a gas chromatography-mass spectroscopy instrument. The k values were in the following order: US/UV/H2O2/ZnO > US/UV > UV/ZnO> UV/H2O2 > UV > US. ZnO concentration of 100 mg/l, malathion initial concentration of 200 µg/l, H2O2 concentration of 30 mg/l, pH of 9, and irradiation time of 105 min were the optimum conditions for degrading malathion by the US/UV/H2O2/ZnO system. Additionally, the optimized parameters were also tested for the treatment of an actual water sample containing the pesticide. As a result, the efficiency of the US/UV/H2O2/ZnO system was higher in the distilled water sample than in the actual water sample.

Abdolmajid Fadaei and Mahdi Kargar