| Folic acid is a trace substance that maintains the normal life and plays an extremely important role in body growth and development.With the strengthening awareness of people’s health,the demand for folic acid has been increasing year by year.However,large amount of wastewater is produced during the production of folic acid,causing serious environmental problems.In order to solve the problems of low efficiency and high processing cost for the treatment of folic acid wastewater in traditional processes,this project studied a fast,efficient and low-cost method for pretreatment of folic acid wastewater,which can effectively remove the COD of folic acid wastewater and improve the biodegradability.In this paper,a novel pretreatment process for folic acid wastewater was constructed,and the folic acid wastewater was provided by a folic acid production company in Qingdao.The effects of various factors on the pretreatment of folic acid wastewater by Iron foam three-dimensional electro-Fenton system(3D-EF)were studied through smallscale experiments,and the best conditions of the pilot reactor were explored at the same time.Meanwhile,the kinetics and mechanism of the reaction were explored,and the compositions of organics as well as biodegradability in the influent and effluent were analyzed.A small-scale pretreatment of folic acid wastewater was conducted using an Iron foam three-dimensional electrode-Fenton system.Single factor experiments and orthogonal experiments were used to optimize the process conditions.The optimum process conditions were as follows: applied current was 300 m A,iron foam loading was 4 g,p H was 3,the initial COD concentration was 10000 mg/L.Under the optimum conditions,the COD removal rate of folate wastewater was 43.52%,and the removal rate of TN was 71.71%.The surface morphology,elemental composition,distribution and valence state of the iron foam were analyzed by means of SEM-EDS and XPS.The results showed that with the progress of the reaction,the surface of the iron foam was gradually eroded and the structure was destroyed,causing the decrease in treatment efficiency with the increase in the number of reaction times.While a minor change in N element content on the surface of foamed iron was observed,therefore,the adsorption of iron foam did not play a significant role in the removal of TN from waste water.Through the research on the yield of active chlorine in the system,the yield of active chlorine in the system was up to 160 mg/L.Simultaneously,the acute toxicity of the wastewater before and after the reaction was tested,and the change of found to be small.After the Iron foam 3D-EF pretreatment of iron foam,the B/C of folic acid wastewater was increased from 0.24 to 0.44,indicating the biodegradability was greatly increased.A pilot reactor was designed on the basis of the above experiments.The Iron foam 3D-EF system was used to treat the folic acid wastewater.The reactor parameters were optimized according to the single factor experiment to obtain the best process conditions.The optimal process conditions were: applied current was 400 m A,iron foam filling amount was 54 g,and the number of plates was 4 cathodes and 3 anodes.Under the optimum conditions,the COD removal rate was 45.5% and the TN removal rate was 75.7%.By LC-MS and fluorescence analysis,the changes of the substances in the waste water after the reaction were detected.It was concluded that the macromolecular organic matter in the waste water before and after the reaction was decomposed into smallmolecule organics,and a good treatment effect was obtained.The concentration of Fe ions in the outer water was tested and it was found that the concentration of iron ions in the water meets the emission concentration specified in the national emission standards.The Iron foam 3D-EF system in this study is a new type of folic acid wastewater pretreatment technology with high processing efficiency and low cost,and has good application value. |
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