Conversion And Utilization Of Heterocyclic Compounds In Wastewater

At present,three-waste treatment has always been a top priority in environmental protection issues.Wastewater not only pollutes a wide range of areas,but also harms human health.Common industrial wastewater mainly comes from pharmaceutical synthetic wastewater,pesticide production wastewater,coking wastewater and so on.Among them,with the rapid development of agriculture,more and more pesticides are needed,and a large amount of waste water from pesticide production will follow.Pesticide fungicide is the second most used pesticide in the world.Research and development of highly effective and low-toxic fungicides have become the focus of many pesticide companies.Because of its high efficiency,stability and other advantages,pyraclostrobin has become the most important fungicide in China.The production process is complicated,and a large amount of waste water containing heterocyclic compounds and other organic substances is generated.Therefore,the COD value of the waste water is high,the toxicity is great,the biodegradability is poor,the components are complex,and the treatment is difficult.How to deal with pyraclostrobin production wastewater efficiently has certain research value.In this study,by optimizing the synthetic process of pyraclostrobin,the intermediates produced by pyraclostrobin and the waste water produced during the production process were collected separately.The waste water in the three processes of reduction,esterification and methylation reactions in the synthesis process is used to determine the main components of the wastewater.After the pretreatment of the wastewater,the organic solvent is recovered;Then,the wastewater is treated with Fenton oxidation.The effects of pH,Fenton’s reagent mole ratio,reaction time,and UV irradiation on Fenton’s oxidation were studied.For the intermediates of heterocyclic compounds,the intermediates are recycled using resin adsorption.The optimum oxidation conditions for pyraclostrobin production wastewater were determined experimentally.The optimal conditions for the Fenton oxidation of wastewater in the reduction step were as follows:pH=1,molar ratio of Fenton reagents(H₂O₂:Fe²⁺)was 10:1,and the reaction time was 15 min;The best conditions for the Fenton oxidation treatment of the production wastewater in the esterification reaction step were as follows:pH=2,molar ratio of Fenton reagents(H₂O₂:Fe²⁺)10:1,and reaction time 30 min.The optimum conditions for Fenton oxidation of the production wastewater in the methylation reaction step were:pH=2,molar ratio of Fenton reagents(H₂O₂:Fe²⁺)is 10:1 and the reaction time is 30 min.Under the optimal oxidation conditions,the COD removal rate was used as a measure for the three wastewaters,and the COD removal rates were 89%,52%,and 82%respectively.The removal rates of COD under ultraviolet irradiation were 92%,59%,and 88%respectively.By comparing XDA-1,XDA-8,and XDA-9 resins for the static adsorption of two heterocyclic compound intermediates in pyraclostrobin production,the use of XDA-8resin for the adsorption of heterocyclic intermediates was determined.Using XDA-8resin at a flow rate of 5 BV/h at 25°C to adsorb the waste water,the XDA-8 resin had a saturated adsorption capacity of 46.10 mg/g and 55.46 mg/g for two heterocyclic intermediates.Resins of a unit mass can be used to adsorb both waste water containing 0.56L and 0.97L of heterocyclic compounds.