Electrocatalytic Degradation Of Organochlorine Pesticides By Novel Fe-ZSM-5 Type Three-dimensional Particle Electrode

Organochlorine pesticides were widely used around the world before the 1980s,due to their bioaccumulation and high toxicity,they caused serious harm to aquatic ecosystems and human health.Although most of the organochlorine pesticides with high residual toxicity such as DDT,666,etc.are banned in many countries,in recent years,organochlorine pesticide residues can still be detected in water,soil and organisms.Since organochlorine pesticides have poor biochemical properties and strong biological toxicity,they cannot be completely degraded in the biological treatment of sewage,there is an urgent need to develop methods that can efficiently degrade organochlorine pesticides.The three-dimensional particle electrode method can generate hydroxyl radicals and other active substances to mineralize difficult-to-degrade organic pollutants into CO₂ and water,at the same time,it has become an important method of water treatment technology because of its unique advantages of high efficiency,wide application range,and low energy consumption.In this experiment,Lindane and Triclosan,which have a high detection rate in environmental water,were used as research objects.The iron-loaded ZSM-5 three-dimensional particle electrode system was constructed to treat the target pollutants,and the following main conclusions were obtained:?1?The ZSM-5 three-dimensional particle electrode?Fe-ZSM-5?loaded with metal Fe was prepared by dipping and roasting.The results show that the main components of the particle electrode are O,Al,Si,Fe and other elements.Most of the Fe elements are present in the particle electrode in the form of iron oxide,the surface of the particle is uniform and dense.The morphological structure of Fe-ZSM-5 before and after the reaction there is no obvious change,but after the reaction,the iron element in the particle electrode will be lost in different proportions.?2?In this thesis,the effects of different current densities,different initial concentrations,different dosages of particle electrodes,different pH values and electrolytes on the degradation of Lindane in the three-dimensional particle electrode system are systematically studied.The results show that with the increase of current density and dosage of particle electrodes,The degradation efficiency of Lindane is improved,thereby shortening the time for complete degradation;The acidic environment is conducive to the degradation of Lindane by the three-dimensional particle electrode;as the initial concentration of Lindane increases,the degradation rate of Lindane gradually decreases,but the absolute amount of Lindane degradation gradually increases.Na₂SO₄ and NaNO₃ promoted the degradation rate of lindane,while NaCl and NaHCO₃ inhibited the degradation rate of lindane.The degradation process of Lindane by the three-dimensional particle electrode system conforms to the first-order reaction kinetics.In addition,Fe-ZSM-5 has good sustainable use,after 7consecutive repeated degradation experiments,the degradation rate of about 99.5%is maintained for 8 hours after electrolysis.?3?Taking the TOC removal efficiency,mineralization current efficiency,energy consumption and dechlorination effect as evaluation indexes,the effects of different current densities and the dosage of Fe-ZSM-5 particle electrode on the mineralization effect of Lindane were discussed.At pH=6.5,the current density is 20mA/cm²,the electrolyte is sodium sulfate 21.1mmol/L,the initial concentration of lindane is 5mg/L,and the TOC removal rate reaches 80.5%after 8 hours of electrolysis.At the same time,the electron spin resonance?ESR?was used to study the change of signal peak and the mechanism of free radical generation under different conditions.The results showed that the Fe-ZSM-5 particle electrode first promoted the generation of H^*free radicals.A DMPO-OH signal peak was detected,indicating the generation of OH^*free radicals.Finally,meteorological chromatography-mass spectrometry was used to detect the intermediate products of lindane degradation,and it was speculated that two lindane may be completely mineralized in the system,and the biotoxicity inhibition rate of the lindane solution for 8 hours of electrolysis was 80.88%.?4?The three-dimensional particle electrode system was studied to degrade the organic chlorine antibacterial agent triclosan.With the increase of current density and input of Fe-ZSM-5 particle electrode,the degradation rate of triclosan was accelerated,and the acidic conditions were favorable to the degradation of triclosan.At a current density of 20 mA/cm²,an electrolyte of 21.1 mmol/L sodium sulfate,pH=3,an initial concentration of triclosan of 5mg/L a particle electrode of 0.05 g,and a reaction of 8 h,the degradation rate of triclosan reached 97.09%And consistent with the first-order reaction kinetics,the rate constant is0.437h^-1.