Study Of Catalytic Wet Peroxide Oxidation And Biological United Treatment Of3,5,6-Trichloropyridin-2-OL Simulated Wastewater

3,5,6-trichloro-2-hydroxy-pyridine (TCP) is an important chemical material, which is widely used in synthesis of chlorpyrifos and chlorpyrifos-methyl. TCP is soluble in water. It is a refractory organics. The production wastewater of chlorpyrifos and chlorpyrifos-methyl is difficult to be treated by microorganism because it contains large amount of TCP, which becomes a difficult problem that bothers the pesticide production enterprises. This paper is taking the TCP simulated wastewater as the research object and using the peroxide as the oxidant, which is stronger on oxidation, to study on the process parameter and mechanism of organic contamination degradation by catalytic wet hydrogen peroxide oxidation technology and to provide theoretical basis and technique reference.Oxidation experiments were conducted in a1L autoclave which can withstand high temperature and high pressure, and the influences of the various factors, such as temperature, peroxide dose and intensity of stir on the treatment efficiency were investigated. The experiment result shows:temperature has a significant influence on the degradation rate, that the degradation rate increase with increasing temperature; the peroxide dose exceed to a certain value, the removal efficiency remained unchanged; within a certain range to increase the stirring rate can improve the efficiency of the reaction. The best operation condition is pH=6, the initial concentration of TCP was5000mg/L, the temperature was200℃, the stirring rate was200r/min, the peroxide dose was15.26ml/L and the removal rate can reach98.5%.The heterogeneous catalyst can improve the TCP removal rate gently. This paper investigated operation parameters of the degradation of TCP by CWPO, using the Cu-Mn-Ce/zeolite supported catalyst made by impregnation method. The experiment result shows that under the catalysis of the catalyst, the requiring temperature of the experiment decreased significantly. The TCP removal rate have reached98%at160℃.The degradation intermediates of TCP by CWPO were inspected by LC-MS and a possible degradation pathway has been inferred. There were six intermediates that can be detected:3,5-dichloro-2,6-dihydroxypyridine,3-chloro-2,5,6-hydroxypyridine,4-amino-2-butenoic acid, maleic acid and oxalic acid. We can infer its degradation pathway: the chlorine atoms of TCP was attacked by nucleophilic substitution reaction of hydroxyl radicals and the TCP transform into multiple hydroxypyridine, which oxidized into4-amino-2-butenoic acid then.4-amino-2-butenoic acid was oxidized and decomposed as maleic acid, and maleic acid was degraded into oxalic acid, last partial organics were mineralized to CO2and H2O.With the pretreatment of catalytic wet air oxidation, TCP simulated wastewater was transformed into organic wastewater containing a lot of organic acid, and various indexes had not met the Sewage Comprehensive Discharge Standard. This paper investigated the optimum condition of biodegradation of the pretreated TCP simulated wastewater. The result shows that the biochemical system can bear the influent concentration of1500mg/L at most when the pH=7. When the HRT=3d, the effluent COD concentration was stability was about350mg/L, which can reach the sewage discharged into the city under water quality standards (CJ3082-1999) emission requirements; When the HRT=5d, the effluent COD concentration was stability after7days and was about90mg/L, which can reach primary standard of Integrated Wastewater Discharge Standard (GB8978-2002); When the HRT=6d, the effluent COD concentration was stability was less than60mg/L, which can reach primary B standard of Discharge standard of pollutants for municipal wastewater (GB18918-2002).