Optimization of pretreatment in pymetrozine production wastewater via reactive distillation and side-stream distillation methods with response surface methodology.

Lots of highly concentrated saline organic wastewater is produced during the pymetrozine production process, causing environmental pollution and waste of resources if discharged directly. Research on actual pymetrozine wastewater treatment is quite scarce. Existing treatment methods of pesticide wastewater usually have disadvantages of long treatment time, low processing efficiency and low recovery rate. To solve these problems, a pretreatment process for pymetrozine wastewater was studied based on material recovery and pollutant degradation. The ammonia conversion process was experimentally investigated by reactive distillation. The reaction product vapor was neutralized and then separated by side-stream distillation. Aspen Plus and response surface methodology were employed to simulate and optimize the operating conditions. Box-Behnken design was used to investigate the individual and interaction effects on methanol purification and sodium acetate removal. Experimental study was carried out on the basis of theoretical simulation data. The result showed that the optimized methanol content on tower top was 99.28% with a yield of 99.95% and methanol content of side withdrawal was 0.01%. The process can be applied for pesticide wastewater treatment to recycle high purity chemical materials, and meets the national sewage comprehensive emission standard.