| Methylthio acetaldehyde oxime also known as the methomyl oxime, which is the key intermediatesfor thesynthesisingof carbamate insecticide methomyl and thiodicarb methomyl.It can’t be treated by the biochemical degradation methodthat the production wastewater, because of its high salt content, high COD value and high toxicity with a foul smell.The water quality belongs to high refractory quality. At present, there is very few reports related to its processing.In this paper, the relevant study was conducted which was mainly aimed at the character of the sewage of one production enterprise in Qingtongxia, Ningxia. Single technical scheme was designed for the recycling products, desalination, eliminate peculiar smell and reduce COD through extraction, freezing and distillation methods. In addition, the treatment effect of different disposal technologies was examined and the related law was summarized. At the same time, it provided the guidance on the environmental protection measures and engineering practical application.The main contents and results are as follows:(1) The extraction recovery process was investigated according to the case that waste water containing a certain amount of products. The ethyl acetate was finally chosen as extraction solvent by comparing several different kinds of extractants because of its high extraction and the role of flavouring for wastewater. The optimal extraction conditions in the process of real production have been explored when the extraction temperature was 20℃, oscillation rate was 180±10 rpm, oscillation time was 20 min, pH value was 9.11 and the ratio of extraction agent dosages and wastewater was 1:10. Under the optimal conditions, the distribution ratio constant (D) of mercaptoacetone oxime was 10.49 in organic phase and water phase, about 84.8% mercaptoacetone oxime was recycled in the process of two-stage cross-flow extraction and the solvent recovery rate could reach 88.4%. The experiment results showed that using ethyl acetate as extraction agent, most of the mercaptoacetone oxime products can be recycled from wastewater.(2) The effect of the freeze concentration technology on the reducing the salt content and COD value duringdealing with the wastewater was studied.The salt migration patterns was investigated-according to the frozen concentrate experiment when the sodium chloride solution content is 18%,and controlling the mining ice timethrough the change rule of salt. We investigated the process of the actual wastewater treatment by suspension freeze concentration method.The optimal conditions have been explored when themechanicalstirring speed was 300 r/min(two leaves stirring paddle 70 mm x 20 mm), refrigerant temperature was 40℃ and crystallization time was 15 min (-30℃)by orthogonal experiments.In orthogonal experiment, the value of salt and COD could decrease by 44% and 57% in optimal experimental group, respectively.Furthermore, the application prospectsof the freeze concentration method in treating wastewater was analysised according to the experiment results.(3) This article also introduced the effect of distillation in the application of wastewater treatment.Firstly, the waste water was extracted by ethyl acetate,and then distillingthe residue.The result showed that the value of COD dropped by 72.2% compared with the distillate and the dope.What’s more, the deodorized treatment method of the tail gas and distillate in the process of distillation was studied.The result showed that the value of COD decreased by 75.0% compared with the distillate and the dope after deodorized treatment and reached the aim ofthe distillate after deodorization treatment was down 75.0% from concentrate COD values.Finally, this paper introduces the treatment method of residual solid material after distillation processing and realize the goal in wastewater treatmentresource. |
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