| With the rapid development of the mechanical processing industry,the use of cutting fluid is increasing.In the process of processing,corresponding waste liquid with high COD concentration,complex composition,and hard to degrade is produced.Although some of them have been reused,but there is still a part that needs to dealt with.Generally,pretreatment was used to reduce the burden of subsequent processing.The persulfate oxidation method is simple to operate,has a wide range of application,and has strong oxidizing properties.However,there are few examples of actual wastewater treatment.In this paper,the actual metal cutting fluid waste water of BYD is treated with coagulation and ultrafiltration,then persulfate is used for oxidative degradation,and the optimal treatment conditions are sought to analyze the persulfate oxidation mechanism.The following conclusions are drawn:(1)The waste water of metal cutting is treated by the method of peroxide degradation combined with pretreatment,coagulation and ultrafiltration,and the optimum p H range is6-8 in the coagulation experiment.The optimum dosage of PAC and PAM was 20g/L and50ml/L,COD removal rate was 80.67%,and the effluent COD value was 7538.4mg/L.The supernatant was ultrafiltered and the removal rate was about 20%.Finally,the thermal activated sodium sulfate oxidation degradation,in the optimized condition PS:12COD0=2.4,p H was about 5,the experimental temperature was 100 ?,the thermal activation time for3 h,cod removal rate was about 96.89%,the effluent COD value was 193.6 mg/L,organic matter was degraded and removed,and the effluent water quality was good.(2)The persulfate dosage is related to the COD value of the initial solution.In this project,PS:12COD0=2.4,more sodium persulfate is used,which increases the cost.In order to solve this problem,it is proposed to use a catalyst to solve.Two kinds of catalysts,activated carbon and Fe SO4·7H2O,were selected in the experiment.The results show that the treatment effect is not very obvious.(3)As time goes on,the S2O82-content decreased,and the UV254 begins to decreased,which indirectly indicated the degradation of macromolecule organic matter,and the corresponding COD removal rate was increasing,they showed the relative consistency.In addition,after sodium sulfate was used in the waste solution,The solution showedstrong acidity,with the reaction,the p H continued to decrease,for the treatment of metal cutting waste liquid continuously provided a strong acidic environment,COD removal rate was also increasing.Ion chromatography was used to analyze the inorganic substances before and after heat-activated persulfate oxidation.The concentrations of Ca2+ and Mg2+ cations were all decreased,and they were all removed as precipitates.The decrease in Cl-concentration indicates that it was oxidized and removed.In addition,a large amount of SO42-appeared after the reaction.It was the products of SO4-· oxidation-reduction reaction.The infrared spectrum and high-performance liquid chromatograms were combined to analyze the products before and after oxidation.Many organic functional groups were degraded,and aromatics were removed or broken down into small molecules or compounds.High-performance liquid chromatograph shows that the peak value after the reaction becomes smaller and the organic matter is degraded,which is consistent with the experimental results of UV254 and COD removal rate measured in the previous experiment. |
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