Study On Electrocatalytic Degradation Of Pesticide Wastewater By Lead Dioxide Electrode

From pesticide manufacturing to formulation industry,to pesticide use,harmful compounds in pesticides are being intentionally or unintentionally released into the water environment.Pesticides remaining in the environment can be bioenriched through the food chain and eventually enter the human body,causing human carcinogenesis,teratogenicity,and mutagenicity,etc.The existence of pesticide wastewater has seriously threatened the coordination of the environment and human health.Therefore,the degradation of pesticide wastewater is great significance to reduce its threat to human health and the environment.In this paper,the electrocatalytic oxidation method was used to degrade the nitenpyram simulated pollutants,and then,on the basis of theory,the process of electrocatalytic oxidation was used to degrade the actual pesticide wastewater,so as to reduce the toxicity of wastewater and provide feasibility for subsequent biodegradation.The influences of applied current density,initial nitenpyram concentration,Na₂SO₄concentration,and p H value on the electrochemical removal of nitenpyram and degradation kinetics were investigated using Pb O₂electrodes as anodes.The results demonstrated that the electrochemical oxidation of nitenpyram follows pseudo-first-order reaction kinetics under different operation conditions,and has the high correlation coefficient.After that,95.44%of nitenpyram and 79.22%of COD could be eliminated from 0.15 mol L^-1Na₂SO₄solution dissolving 75 mg L^-1nitenpyram under 70 m A cm^-2at7.0 p H.Moreover,TOC removal capability and mineralization current efficiency（MCE）were also investigated in the degradation of nitenpyram by lead dioxide electrode.With the progress of electrocatalysis,MCE gradually decreased,and the TOC removal rate reached 75.29%at the degradation time of 120 min.Ultimately,HPLC and HPLC/MS were adopted to discover the degradation byproducts during the nitenpyram oxidization process,and up to fourteen byproducts were successfully identified.Then a typical nitenpyram degradation pathway was proposed based on these byproducts,which was composed of two divided parallel sub-routes.In brief,electrochemical advanced oxidation processes using Pb O₂electrode as anode have great perspective in efficient decontamination of pesticide nitenpyram in aqueous solution.The real pesticide wastewater was degraded by electrocatalytic oxidation.The influence of several process variables of electrocatalytic oxidation,such as current density,p H and electrode gap on chemical oxygen demand（COD）removal ratio was investigated.The results indicated that COD removal ratio reached 86.96%,and the COD decreased from 7519 mg L^-1to 980 mg L^-1after 120 min electrolysis under the degradation parameters of current density of 4 A dm^-2,p H value of 4 and plate spacing of1.0 cm.The electrocatalytic degradation of real pesticide wastewater followed pseudo-first-order kinetics.When electrocatalytic degradation was performed for 120 min,the color of the real pesticide wastewater gradually faded,the degree of mineralization increased,the TOC removal rate was 74.21%,and the BOD₅/COD increased from 0.18to 0.43.The organic load of the wastewater was reduced,and the biodegradability was improved,which provided feasibility for subsequent biodegradation.When the COD removal rate of pesticide wastewater reached 86.96%,the energy consumption was 129kw h m^-3.Overall results indicated that electrocatalytic oxidation could effectively degrade pesticide wastewater and improve its biodegradability.