Parameter Optimization Of Fenton Process For Treating Cutting Fluid Wastewater And Study On Heat Treatment Behavior Of Residual Sludge

As hazardous waste,national regulations require companies to dispose of waste cutting fluids in a reasonable manner.In order to reduce the disposal cost,enterprises often reduce the amount of waste cutting fluid.Considering the characteristics of waste cutting fluid with high COD concentration and poor biochemical properties,in order to enhance the treatment of waste cutting fluid and reduce the cost of hazardous waste disposal for enterprises.In this study,based on the combined process of coagulation and Fenton oxidation,the effect of each reaction factor on the treatment of cutting fluid wastewater by Fenton oxidation was studied in depth,and the residual sludge generated by the Fenton process was reduced by heat treatment to reduce the amount of secondary hazardous waste generated by the wastewater treatment process and to reduce the cost of hazardous waste disposal for enterprises.Meanwhile,by TG,DSC test to obtain the thermal properties of Fenton sludge,XRD to analyze the crystal phase change of Fenton sludge before and after heat treatment,EDS to obtain the element content of Fenton sludge before and after heat treatment,and SEM to ascertain the morphology of Fenton sludge before and after heat treatment was observed.The chemical properties of Fenton sludge before and after heat treatment were analyzed by XPS and FTIR as well as a series of characterization and analysis techniques,in order to complete The study of the properties and heat treatment process of Fenton sludge was completed.Finally,a thermodynamic analysis of the thermal treatment behavior of Fenton sludge was performed,and a thermal analysis model that can optimize the actual thermal treatment control parameters was developed to provide a theoretical basis for resource treatment or incineration and disposal of Fenton sludge.The main research results are as follows:（1）The demulsification pretreatment of waste cutting fluid showed that PAM and PAC had obvious demulsification effects on waste cutting fluid.The optimal treatment conditions obtained by single factor experiment were PAC adding 6 g/L and PAM（concentration of 2‰）adding 2 m L/L,and the COD_cr removal rate reaching 57.2%under this reaction condition.（2）Fenton oxidation treatment showed that the Fenton oxidation process can effectively degrade the pollutants in the cutting fluid wastewater after demulsification.According to an orthogonal experiment and single factor experiment,the optimal reaction conditions for treating demulsified cutting fluid wastewater by Fenton oxidation method were as follows:Fe²⁺:H₂O₂（mass ratio）=1:2,H₂O₂ dosage=70m L/L,initial p H=5.5,H₂O₂ dosage interval=25 min（reaction time:100 min）.The COD_cr removal rate was the highest 81.7%,S/C value was the lowest 7.5×10^-2 m L/mg,and it had some resistance to water quality fluctuations.（3）Through XRD and EDS characterization tests and TG and DSC thermal properties tests,it can be seen that the main components of Fenton sludge were amorphous ferric hydrate and Na₂SO₄.There were two main stages of weight loss in Fenton sludge during heat treatment,both of which occur before 500℃.The weight loss of the first stage was mainly due to the loss of adsorbed water and interlayer water in Fenton sludge and the pyrolysis of organic matter.In the second stage,the main reason for weight loss was the transformation of iron hydrate（HFO）to Fe₂O₃ and Fe OOH in Fenton sludge,in which the main product was Fe₂O₃ and only a small amount of Fe OOH was generated.（4）MDA thermodynamic modeling was adopted for the heat treatment process of Fenton sludge.According to the DTG curve style,a double Gaussian function was selected（the fitting R² of each heating rate reaches more than 98%）to split the overlapping rate peaks in the reaction into two independent stages.The apparent activation energy of the first stage was 26.5351 k J/mol,with an average R² of 96.28%.The apparent activation energy of the second stage was 85.6384 k J/mol,with an average R² of 96.64%.The average△E/E₀ value of the two stages was less than 5%.The thermodynamic models of the two stages were established successfully.The successful establishment of the thermodynamic model not only reveals the thermodynamic mechanism of the Fenton sludge heat treatment process,but also provides a great reference value for the application conditions of Fenton sludge resource recovery.