| Nowadays, the chemical industry wastewater, especially the pesticide chemical has become one of the significant tasks to the water environment protection in China.Sodium 3,5,6-trichloropyridin-2-olis not only one of the key intermediates to the synthesis of Chlorpyrifos(a kind of pesticide), but also a chelate flotation agent. The process of its production will produce a difficulty biodegraded organic wastewater that is with the features of high organic concentration, high toxicity and chromaticity. Generally, the chemical/biological pre-treatment combined biological treatment is adopted to treatment the wastewater. However, the Ultrasonic/Fenton process which is a combination of the free radical oxidation, pyrolysis and supercritical water oxidation together, is one of the most efficient pre-treatment processes.Factors that might affect the treatment efficiency of Ultrasonic/Fenton process and the optimization of them were investigated, based on an organic industrial wastewater collected from a regional sodium 3,5,6-trichloropyridin-2-ol process site. The influence of process parameters on the organic matter removal were confirmed through the single factor experiments. Meanwhile, the advantages of Ultrasonic/Fenton process were analyzed. Based on the experimental result, the optimization of Ultrasonic/Fenton process and establishment of the COD removal model were conducted, and the optimal process parameter was confirmed. Model verification, water quality evaluation, and degradation pathway of organic matter under the optimal process condition were researched.The main conclusions are as follows:① The influences of process parameters on Ultrasonic/Fenton processFactors such as dosage of H2O2 and Fe2+, initial p H, reaction time and ultrasonic power that might affect the COD and chroma removal of Ultrasonic/Fenton process were investigated. Decoloration efficiency was almost not influenced by the variation of process parameter. It was because that the disperse Cu particle accounting for the chroma of wastewater which could be removed by coagulating sedimentation.② The comparison of Ultrasound, Feton and Ultrasonic/FentonThe changes of COD removal efficiency during the wastewater treatment using Ultrasound, Fenton and Ultrasonic/Fenton processes were investigated respectively. Based on the results and dynamic analysis, the synergistic effect of Ultrasonic/Fenton process was discussed. Differences of H2O2, Fe2+dosage and reaction rate between Fenton and Ultrasonic/Fenton were compared.③ Optimization of the Ultrasonic/Fenton processResponse surface methodology(RSM) was used in this study to optimize the process parameters of Ultrasonic/Fenton process. Based on Box-Behnken Design(BBD), a regressive model for COD removal efficiency in terms of H2O2 dosage, Fe2+dosage and reaction time was developed by Design Expert. It was significant. The effect of Fe2+dosage on COD removal efficiency was greatest,and the interactive effect of Fe2+dosage and reaction time was significant. The quality indexes of effluent can reach national standard. Moreover, the dosage of H2O2 and Fe2+ per COD removal load was relatively less.④ Process characteristic on wastewater using Ultrasonic/Fenton processThe main organic components of wastewater were cholorobenzene and chloroform, and the main organic components effluent were cholorobenzene, chloroform, chloromethane, chloroethane and 1,1-dichloroethylene, according to the production process and results of GC-MS. Based on above results, degradation pathway of organic matter under the optimal process condition were discussed.At present, research of Ultrasonic/Fenton process mainly focuses on simulated wastewater and was carried out in a laboratory scale. In view of the complexity and polytropy of industrial wastewater, the study of process parameters of Ultrasonic/Fenton process and its optimization based on industrial wastewater was significative. The research results could provide certain technical reference to the treatment of similar industrial wastewater. |
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