Application Study Of Combined Coagulation-Fe/C Micro-Electrolysis-Fenton Process For The Treatment Of Water-based Cutting Fluid Wastewater

Cutting fluid is a liquid widely used in the machining process of the modern machining industry,whose role is to cool and lubricate the machining device,with good cooling and lubrication,rust and corrosion prevention,oil removal,and cleaning functions,usually consisting of tensile oil,surfactants and various additives.The wastewater result from cutting fluid without treatment will cause aquatic life poisoning,human cancer and other risks.Therefore,the pretreatment of water-based cutting fluid wastewater before biochemical treatment is particularly important.The current treatment technology mainly includes air floatation,coagulation,oxidation,biological treatment,etc.However,with the improvement of water quality requirements,a single process cannot meet the treatment requirements.So the combination of two or more kinds of technologies are urgently needed for treatment.In this paper,a water-based cutting fluid wastewater from a machining plant in Nanchang is used as the research object,and a combination of coagulation-Fe/C micro-electrolysis,coagulation-Fenton oxidation and coagulation-Fe/C micro-electrolysis-Fenton oxidation processes are used for purification and treatment research to make the water meet the standards.The experiments start with single-factor experiments on coagulation and sedimentation,and three sets of parallel experiments are conducted for each influencing factor to investigate the optimal combination of coagulant type and dose,settling time,p H,etc.The subsequent effluents are subjected to single-factor experimental studies of Fe/C micro electrolysis,Fenton oxidation,Fe/C micro electrolysis-Fenton oxidation,and response surface optimization parameters,to investigate the optimal combination of Fe/C micro electrolysis and Fenton oxidation.electrolysis and Fenton oxidation technologies were studied separately for degradation kinetics.Research indicates:（1）The single-factor experiment of coagulation and sedimentation shows that the dosage of PFS and PAM are 1.3 g/L and 30 mg/L respectively,the sedimentation time is 3 hours,and the p H value is 8.At this time,the COD removal rate is 27.02%;The Fe/C micro-electrolysis single-factor experiment is carried out in the effluent of the product.The results show that the mass ratio of Fe/C is 1:4,the total mass of Fe and C is 500 mg/L,the p H was 4,and the electrolysis time is 120 min.At this time,the COD removal rate is 18.2%;the effluent after coagulation is subjected to Fenton oxidation single factor experiment,and the results show that the dosage of H₂O₂is 1.96 mol/L,the dosage of Fe²⁺is 27.44 mol/L,the p H is 3,and the reaction time is 120 min.At this time,the COD removal rate of the coagulation sedimentation-Fe/C micro-electrolysis process combination single factor experiment is45.19%;the COD removal rate of the coagulation-Fenton oxidation combination single factor experiment is 87.07%.（2）Based on the design principle of the Box-Behnken design experiment,Fe/C micro-electrolysis is optimized,and it shows that the mass ratio of Fe/C is 3:8,the total dosage of Fe/C is 499 g/L,the p H value is 3.7,and the electrolysis time is 117.94 min,the removal effect of COD is the best,which is 34.97%.After verification by three groups of parallel experiments,it was found that the error of the prediction result was only 0.48%higher than the actual treatment.The interaction analysis shows that the order of the factors is p H>Fe/C mass ratio>reaction time>Fe/C dosage;The COD removal rate of the optimized coagulation sedimentation-Fe/C micro-electrolysis process combined experiment is 53.14%.Similarly,the optimized Fenton oxidation shows that the H₂O₂/Fe²⁺molar ratio is 14,the amount of H₂O₂is175 mmol/L,and the p H When the oxidation time is 3 and the oxidation time is 115 min,the removal effect of COD is the best,which is 86.85%.The interaction analysis shows that the order of the factors is reaction time>H₂O₂/Fe²⁺molar ratio>H₂O₂dosage>p H;optimization The COD removal rate of the subsequent coagulation-Fenton oxidation combined experiments was 89.8%in total.（3）Preliminary studies on the degradation kinetics of the Fe/C micro-electrolysis after coagulation and Fenton oxidation experiments with optimized parameters were carried out respectively.The kinetic law of this time is defined as satisfying the zero-order reaction kinetic law,and the model is C_t=-10.4776 t+5418.8072;the kinetics of the Fenton reagent meets the third-order reaction kinetic model,and the reaction degradation model is C_t=0.0029 t-0.0169.（4）The Fenton oxidation in the coagulation-Fe/C micro-electrolysis-Fenton oxidation combined process was applied to the optimized coagulation sedimentation-Fe/C micro-electrolysis optimal experimental condition effluent obtained in the previous study,and the Fenton oxidation was obtained.The single factor results show that the dosage of H₂O₂is 1.47mol/L,the p H is 3.5,the oxidation time is 90 min,and the COD removal rate is 89.17%.When the p H is 2.94 and the reaction time is 93 min,the removal rate of COD is 91.6%.After the actual three groups of parallel experiments,it was found that it was only 0.63%lower than the experimental value,and the final effluent COD was 275 mg/L,reaching the second level.The effluent standard and the interaction analysis shows that the order of the influencing factors is H₂O₂dosage>reaction time>p H;through the cost calculation of the agent,it is concluded that the coagulation-Fe/C micro-electrolysis-Fenton oxidation combined process is economical and reasonable in price,and the technical effect is useful.It costs 0.513 RMB to treat 1m³of the water-based cutting fluid wastewater,and the optimized coagulation-Fe/C micro-electrolysis-Fenton oxidation combined experiment can remove 96.41%of the total COD from the water-based cutting fluid wastewater.