Study On The Influencing Factors Of 2,4,6-tcp Degradation In Bi-oxidants System Catalyzed By Iron Hydroxide In Growth Ring

Chlorophenols widely exist in wastewater,sludge,surface water and groundwater,and are a series of typical water pollutants.Chlorophenols,especially in the presence of humic acid,are disinfection by-products?DBPs?in drinking water.Chlorophenol has "three carcinogenic"?carcinogenic,teratogenic,mutagenic?effects and genotoxicity.It is also an endocrine disruptor.The more chlorine substituents,the more toxic chlorophenol is,the more difficult it is to be biodegraded.The removal efficiency by conventional water treatment technology is usually not ideal.Among them,2,4,6-trichlorophenol?2,4,6-TCP?,as a representative of all chlorophenols,has adverse effects on human nervous system and respiratory system,which will bring many health problems.The heterogeneous persulfate system has been proved to be economical and effective in the treatment of refractory organics such as chlorophenols.The formation of growth ring in urban water supply network is inevitable.The main components of growth ring,that is goethite??-Fe OOH?and lepidocrocite??-Fe OOH?can be regarded as a misplaced resource.When cleaning and replacing the pipeline,the extracted growth ring can be used as the catalyst of heterogeneous oxidation system,which is more abundant and economical than the catalyst prepared artificially.In this study,persulfate and hydrogen peroxide?H₂O₂?including persulfate?PMS?and persulfate?PDS?were used to form a bi-oxidants system.Goethite and lepidocrocite were prepared in the laboratory to simulate the actual growth ring composition in the actual pipeline,and catalyzed the degradation of TCP by hydrogen peroxide/persulfate bi-oxidants system.It provides a new idea for the effective use of growth ring to remove chlorophenols in drinking water,and is of great significance to ensure the water quality safety of water supply network.The degradation efficiency of 2,4,6-TCP by bi-oxidants and double catalysis system,single oxidation system and single catalysis system were compared respectively.The synergistic effect between PDS/H₂O₂ and the complex mechanism between PMS/H₂O₂ system were explained.A new kinetic model for heterogeneous system is proposed.K value and Span value are used to reflect the degradation rate and degradation rate of the system respectively,and to eliminate the influence of induction period,so as to provide a basis for quantitative analysis of factors affecting the degradation efficiency of heterogeneous system.The effects of oxidant and catalyst concentration and molar ratio,pollutant concentration,initial p H value of the system and chloride ion on the degradation of 2,4,6-TCP by PDS/H₂O₂ and PMS/H₂O₂ were studied.The best treatment conditions of PDS /H₂O₂ system were oxidant dosage and 2,4,6-TCP molar ratio of 50/1,H₂O₂:PDS=1:1,catalyst dosage is 0.50g/l,goethite and lepidocrocite mass ratio is 1:1,the degradation rate and degradation rate of goethite and lepidocrocite are higher,and the degradation rate can reach 70.6% in 9h.There was no inhibition on the oxidation system at high concentration.Through the orthogonal analysis,the best degradation conditions are as follows: adding PMS only,the ratio of oxidant to 2,4,6-TCP is 5/1,only using lepidocrocite as catalyst,the degradation rate and degradation rate of PMS/H₂O₂ system are good,the degradation rate of 6h is 86.4%,9h is 91.3%.The pH adaptability of PDS/H₂O₂ system was poor,and chloride ion inhibited the system.The higher the concentration of chloride ion,the more obvious the inhibition.PMS/ H₂O₂ system is more adaptable to p H,and chloride ion can promote the degradation of 2,4,6-TCP.At the same time,compared with PDS/H₂O₂ optimal oxidant dosage and 2,4,6-TCP molar ratio of 50/1,PMS/H₂O₂ optimal conditions only need to reach 5/1,consumption of oxidation dose is less,and the product mineralization is complete after reaction.In the process of urban tap water supply,chlorine ion will be introduced into chlorine disinfection,and PMS/H₂O₂ system will have more practical application advantages.However,PMS/H₂O₂ system has the best catalytic effect when only adding lepidocrocite,so there is also the problem of separating goethite and lepidocrocite in the growth ring in practical application.