Study On The Treatment Process Of Methyl Benzotriazole Production Wastewater

In this study,we focused on the treatment of methyl benzotriazole production wastewater from a chemical company in Baiyin city.This wastewater characterizes in high salt content,high COD_Cr and low biodegradability.Moreover,it shared a property of colloid wastewater.According to these characteristics,the wastewater was pretreated by using coagulation sedimentation,Fenton oxidation and their combined processes,and the related experiments were carried out.The thesis mainly includes the following detailed contents:（1）By the result of single-factor experiment and orthogonal experiment of the coagulation and sedimentation,ferrous sulfate can eliminate COD_Cr from wastewater remarkably;p H,coagulant dosage and stirring speed all had impact on the coagulation and sedimentation process of wastewater;When p H=4,the dosage of ferrous sulfate was 4 g/L,and the rapid stirring speed was 150 r/min,the removal efficiency of COD_Crin wastewater by coagulation sedimentation was the best and was 44.27%.EDS energy spectrum and infrared spectroscopy（FT-IR）were employed to analyze the sludge formed in coagulation and sedimentation.It was indirectly found that o-toluenediamine and sodium methyl benzotriazole in the wastewater were effectively settled.（2）Single factor experiment and orthogonal experiment of Fenton oxidation were performed and showed the maximum removal rate of COD_Cr in wastewater reaches84.28%.And the corresponding removal conditions were as follows:initial p H=3.5,m（H₂O₂）was 65 ml/L,n（H₂O₂）:n(Fe²⁺)ratio was 45:1 and reaction time was 60 min.In addition,the three-order kinetics was employed to describe the process of Fenton oxidation and can well fit the process of Fenton oxidation.（3）Through the experimental study and cost analysis on the treatment of methyl benzotriazole production wastewater by the combined process of coagulation sedimentation and Fenton oxidation,the results indicated that the optimal reaction conditions were as follows:m（H₂O₂）was 35 ml/L（dosing one time）,and the reaction time was 60 min.In addition,the coagulation sedimentation-Fenton oxidation combined process had a synergistic effect.The effluent of the coagulation and sedimentation process contained stable Fe²⁺and the p H value was about 3.51,which provided good reaction conditions for Fenton oxidation.The treatment effect that combined process had on methyl benzotriazole production wastewater outweighed than that of a single Fenton oxidation process.Meanwhile,the combined process increased B/C value of the wastewater dramatically which was 5.75 times of the raw water.Moreover,the combined process was more economical and practical than the Fenton oxidation process,and it could save 49.45 yuan per ton of wastewater.（4）The sodium sulfate obtained by cooling crystallization process can meet the relevant requirements in“Anhydrous sodium sulfate for industrial use”[GB/T 6009-2014].In this paper,the proposed coagulation sedimentation-Fenton oxidation process can remove the pollutants in the production wastewater of methylbenzotriazole efficiently,which is significant for the realization of waste salt reduction.