Study Of Wet Air Oxidation For Treatment Of Fomesafen Wastewate Of Pesticide Production

Fomesafen has been widely used due to their characters of high-efficiency, lowtoxicity to mammals and low residue in the environment. Fomesafen productionwastewater is a typical high-concentration organic wastewater of hard biodegradation.The producing wastewater contains high3,4-dichlorobenzotrifluoride,dimethylsulfoxide, toluene,sulfuric acid,methyl,sulfonamide and halogenated agents.By takingthe actual-producting wastewater of fomesafen pesticide as the subject,we studyapplication of organic contamination degradation were carried out by wet oxidationtechnology roundly in this paper in order to solve the problem for enterprise and toprovide a efficient way for the treatment of high concentrated and difficult degradedwastewater. In this study, fomesafen was chosen as the target pollutant to study thedegradation of pollutant, which will provide the theoretical reasons.Oxidation experiments were conducted in a reaction kettle which can stand withhigh temperature and high pressure. The effect of main reaction conditions,such asreaction temperature,oxygen partial pressure,stirring speed and pH on the wastewatertreatment efficiency were investigated.The reaction temperature was a key factor ofinfluence on the efficiency of the WAO reaction.Oxidation reaction may besignificantly limited by the amount of oxygen.And as oxygen pressure exceeded to acertain value,COD removal efficiencies remained unchanged. The effect of pH oninfluent of the WAO reaction was relatively small.COD removal efficiency will reach45%under optimal conditions.Moreover,other indicators,such as Ammonia,TOC,chroma,BOD₅also had a corresponding improvement.Wet peroxide oxidation（WPO）which totally used hydrogen peroxide as oxidantwas developed.The results proved the efficiency of WPO was influenced by peroxidedosage、temperature and pH.WPO was found to have a higher removal efficiency thanthe conventional treatment.COD removal efficiency reached65%with3Mpa oxygenpartial pressure and200rpm/min at250℃under pH5.1conditions.Characteristicpollutants and intermediate in the fomesafen pesticide wastewater also be studied.WPO reaction have high efficiency to dimethyl sulfoxide（DMSO）.Thereaction dynamics、activation energy and thermodynamics for wet peroxide oxidationof benzenewere investigated in the reactor.Catalytic wet air oxidation（CWAO）can improve the COD removal effieiencygreatly in a relatively mild conditions.The complex oxide catalysts of TiO₂-CeO₂wereprepared by the co-precipitation method and applied to the treatment of pesticidewastewater of fomesafen production by wet air oxidation.The result showed catalystcan increase the COD removal effieiency greatly. In addition,the characteristicofcatalysts were tested by XRD. Data revealed the catalyst crystalline structure andidentified catalyst CeO₂and TiO₂by XPS;data revealed the different valence changeand binding energy of Ti,Ce and O,and measured their respective bindingenergy.Furthermore, the degradation of2–chlorophenol was studied by the WAOwith the above catalyst. The results showed that the2–chlorophenol could beeffectively removed with the catalyst.