Studies On Degradation Of Acephate By Advanced Oxidation Processes

Long-time and large-scale production and use of pesticides not only cause serious environmental pollution but also directly affect human, animals and plants through the pesticide residues in food and forage. In this thesis, the degradation of acephate by three different advanced oxidation processes including photoelectrocatalytic via ZnO thin-films, UV/Fenton method and UV/K₂S₂O₈ method were studied. Various factors influencing the degradation were studied to explore the optimal conditions which could provide some scientific basis for the elimination of environmental pollution of acephate.The main contents and conclusions were as follows.(1) Photoelectrocatalytic degradation of acephate by ZnO thin-films: ZnO thin-films were prepared by the sol-gel method. The photoelectrochemical properties, surface morphology and structure of ZnO thin-films were characterized with photocurrent response, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). ZnO thin-films were utilized as the working electrode to study the photoelectrocatalytic degradation of acephate. The results showed that ZnO thin-films electrode could effectively degrade acephate under UV irradiation in the presence of H₂O₂. The 180-min photoeletrocatalytic degradation efficiency for 0.1mmol/L acephate reached 89.6% under the conditions of 10.0mmol/L H₂O₂, external bias potential 1.2V, pH 5.4 and 0.01mol/L Na2SO₄.(2) Degradation of acephate by UV/ Fenton method: The UV/ Fenton method was compared with traditional Fenton method. The degradation efficiency was found to be greatly enhanced under UV irradiation. The results demonstrated that 60-min degradation efficiency for 0.1mmol/L acephate reached up to 92.8% under the following conditions: 2.0mmol/L H₂O₂, 0.02mmol/L Fe²⁺ and pH 3.0 .(3) Degradation of acephate by UV/K₂S₂O₈ method: K₂S₂O₈ could be dissociated to generate S2O82- in solution, and was further decomposed to more oxidative species·SO₄- under UV irradiation. Thus, the degradation efficiency for acepate was significantly enhanced. The results showed that 99.3% of 0.1mmol/L acephate was degraded by UV/K₂S₂O₈ method after 30-min treatment under the conditions of 1.0mmol/L K₂S₂O₈ and pH 3.0.