The Study On Electrochemical Combined Treatment Process Of 2,4-D High Salt Pesticide Organic Wastewater

2,4-D,2,4-dichlorophenoxyacetic acid,is a phenoxycarboxylic acid herbicide,which is widely used for removing weeds worldwide.However,due to the concentration of organic compound and inorganic salt is high in 2,4-D wastewater and the composition of the wastewater is complex,it is difficult to treat the wastewater properly,its composition includes raw materials phenol and 2,4-dichlorophenol,byproducts glycolic acid and sodium chloride,product 2,4-D,a single wastewater treatment method can not meet the wastewater treatment standard.Therefore,based on the water quality information of the wastewater produced from 2,4-D,a combined electrochemical treatment method of 2,4-D high salt organic wastewater is investigated in this paper.Combined with various wastewater treatment methods,this paper explores and optimizes experimental parameters to achieve the best treatment efficiency.The main research work of this paper is as follows:（1）Removal of phenolic substances.Firstly,hydrochloric acid was used to adjust the p H of wastewater to 1～3,and recovered part of the organic matter.After liquid separation,phenolic substances were further separated and recovered by extraction method.The results indicated that when ethyl acetate was used as extraction agent,p H was 1～3 and ratio of oil/water volume ratio was 1:2,the extraction efficiency was the best.The extraction efficiency of phenol and 2,4-dichlorophenol was 97.7%and 99.9%respectively.After extraction,the extractant ethyl acetate and phenolic substances were separation and recovery by vacuum distillation.（2）Removal of glycolic acid.Glycolic acid was separated by calcium salt precipitation method.The reaction between calcium salt and glycolic acid can produce calcium glycolate precipitation.The results indicated that when calcium hydroxide was used as calcium salt precipitator,molar ratio of calcium hydroxide and glycolic acid was 1:2,the p H was 2,the stirring time was 2 h and repeated the precipitation the removal efficiency can get the best result.The removal efficiency of glycolic acid in the filtrate was 97.24%.After drying,the purity of calcium glycolate was 82%by HPLC.Finally,70%of glycolic acid solution was prepared by acidification,it can be used as a cleaning agent,this achieved the purpose of separation and recovery of glycolic acid.（3）Desalination by electrodialysis.The high content of inorganic salt Na Cl in wastewater was removed by electrodialysis,and the degree of Na Cl removal was evaluated by conductivity of the fluid.The purity of removed Na Cl was 99.08%detected by Ag NO₃titration,the Na Cl was gained after evaporation,concentration,crystallization and drying.Finally,about 80%of the Na Cl in the wastewater was recovered.（4）Electrochemical oxidation degradation of 2,4-D.The influence of different electrode species,current density,Na Cl concentration,p H and other factors about the degradation effect were studied and compared.The results indicated that when Ti/Ru-Ti-Sn electrode was used as the working electrode,titanium mesh as the counter electrode,the current density was 50 m Acm^-2,p H=1.5 and the concentration of Na Cl was 0.10 mol·L^-1,the degradation efficiency of 2,4-D can reach the best,after degradation,all phenolic substances and 2,4-D could be removed.（5）In conclusion,This combined electrochemical treatment method not only achieved the effect of wastewater treatment,but also realized the recovery and reuse of organic matter and inorganic salt in 2,4-D wastewater.After cost accounting,the recovery benefit can offset the cost of wastewater treatment and produce a certain surplus.