Degradation Mechanism Of Prometon And Hexazinone In O₃/H₂O₂ AOP

Endocrine Disrupting Chemicals (EDCs) is a kind of pollution which has been paid worldwide attention in recent years. At present, there are more than 70 kinds of pollution are validated as EDCs, 60% of which are pesticides and their metabolites. Endocrine disrupting pesticides are detected in both groundwater and surface water, even including some forbidden types.The investigation to scavenge pesticide is significat as they are hard to remove effectively by general water treatment techniques.In this experiment,prometon and hexazinone are degraded in AOP and the removal effect was represented by the pseudo-first-order rate constant of them.The effect of molar ratio of H₂O₂/O₃, temperature, pH, original concentration of pollutant were discussed in this investigation.Meanwhile, the influence of different water qualities were preliminarily discussed.Forthermore,direct and indirect kinetic and degradation paths were investigated .The contents are as follows:1)The effect of molar rate of H₂O₂/O₃, temperature, pH, original concentration of pollutant were discussed in this investigation.The results indidated that,when original concentration of prometon is 2mg/L,concentration of ozone is 13mg/L, H₂O₂/O₃=0.7,temperature is 26℃,the maximum rate constant of prometon is 0.14min^-1; original concentration of hexazinone is 3mg/L,concentration of ozone is 13mg/L, H₂O₂/O₃=0.5,temperature is 26℃,the maximum rate constant of prometon is 0.075min^-1.The original concentration of pollutant range from 0 to 10mg/L the absolute quantitative removal increase with the concentration increased;2)The impact of pH to degradation of hexazinone is obviously .During the experiment, concentration of hydrogen peroxide and hexazinone were analyzed at regular intervals. The consumption of H₂O₂ is directly proportional to the removal of hexazinone. Hence, the addition of H₂O₂ is significant to scavenge of hexazinone;3)The degradation rate of prometon and hexazinone were measured in tap water and Milli-Q water(pH value is original and molar ratio of H₂O₂/O₃ is 0.7and 0.5 respectively).Degradation rate are faster in tap water than in Milli-Q water .Compared with 0.148min^-1and 0.075min^-1 which is maximum degradation rate constant of prometon and hexazinone without HA,the rate constants degraeased to 0.070 min^-1 and 0.024 min^-1 when the concentration of HA is 10mg/L; when the HCO₃- concentration is 200mg/L, the constant rate constants are 0.092 min^-1and 0.020 min^-1 respectively;4)The direct and indirect oxidise kinetics are investigated by adding radical inhabitator TBA and competitively reacting with phenol. The results show that indirect oxidation is the main process of prometon and hexazinone degradation.Contribution of ozone molecular in oxidation of prometon in O₃/H₂O₂ system is 8.1% ; The contribution of ozone in oxidation of hexazinone in ozone system and O₃/H₂O₂ system is 28.6% and 5.4%.5)The results of HPLC,IC,GC-MS and HPLC-MS showed that triazine ring in prometon and hexazinone were destructed and the terminal products are HNO₃, H₂O, CO₂ as nitrate was detected by IC.