Study On Treatment Of Water-based Waste Cutting Fluid By Coagulation-Ion Exchange-Fenton Oxidation Processes

Cutting fluid is a common industrial liquid,plays irreplaceable-roles of cooling,lubrication and other functions in the process of machining.Water-based cutting fluid has a higher current market share than those of other types.During the use of cutting fluid,a large amount of high-concentration refractory organic waste fluid(wastewater)will be produced.If not be properly treated,it will cause great harm to the ecological environment and the human health.Secret formulation and complex composition of the cutting fluid make it extremely difficult to treat its wastewater.Therefore,searching practical and efficient method for cutting wastewater treatment has become a focus of current research.In this study,a typical water-based cutting waste fluid generated in mechanical processing is selected as the research object.Concentration of the chemical oxygen demand(COD),ammonia nitrogen(NH3-N)and total phosphorus(TP)of the wastewater is 11,000 mg/L,768 mg/L and 32 mg/L,respectively.Coagulation-ion exchange-Fenton reagent oxidation as the basic treatment processes were developed,and the experimental conclusions are as follows:(1)Aluminum sulfate(A12(SQ4)3·18H2O,AS)is more suitable as the coagulant for the wastewater than crystalline aluminum chloride(AlCl3·6H2O,AC).Since the wastewater itself is alkalescent,the hydrolysis of the coagulant itself can effectively reduce the pH value of the wastewater.Therefore,in this study,coagulant is directly added to the wastewater,where the dosage of coagulant can be determined by controlling the pH value of the solution.When the pH is 6.3,where the mass concentration of AS is 12 g/L,the coagulation treatment achieves a high removal of COD and the highest removal of TP,m eanwhile it doesn't introduce a large amount of aluminum ions(Al3+)to the subsequent treatment.After the coagulation,COD and TP of the wastewater can be lowered to about 6500 mg/L and 0.04 mg/L,respectively.The concentration of TP achieves the first-level standard of the Sewage Comprehensive Discharge Standard of China(GB8978-1996).(2)001×7 gel form strong acid styrene cation exchange resin,001 x7H gel form strong acid styrene cation exchange resin,D113 macroporous weak acid acrylic cation exchange resin,201 gel form strong alkaline styrene anion exchange resin and D318 macroporous weak alkaline acrylic anion exchange resin were tested for adsorption of the wastewater.It was found that 001×7H resin and 201 resin have higher COD removal for the wastewater after coagulation treatment,and could also remove most of the NH3-N.Through the regeneration test,it was found that the regeneration ratio of 001×7,001×7H,D113,201 and D318 resins is 85.86%,82.80%,90.09%,76.97%and 89.88%,respectively,among which the regeneration ratios of D113 resin and D318 resin are highest.After comparison of the adsorption and the regeneration,it is finally determined that 001 x7H resin and 201 resin were selected for the adsorption treatment of the effluent from the coagulation.COD and NH3-N of the wastewater from the coagulation can be reduced to about 4000 mg/L and 208 mg/L with the treatment of the 001 ×7H resin.And they can be further reduced to about 1100 mg/L and 186 mg/L with the treatment of the 201 resin.(3)The efficiency of single Fenton oxidation treatment is low.As the coagulation effluent has strong UV absorption,the strengthening effect of UV is not obvious.It was found that glow discharge can effectively improve the reaction efficiency of the Fenton oxidation.Adjust pH of the coagulated effluent to 2.5 and add 9.0 g/L H2O2 and 1.0 g/L FeSO4·7H2O to it.After 1.0 h of glow-discharge,and then standing under natural light for 48 h,COD of the coagulated effluent can be reduced to 1538 mg/L.As the suitable pH for Fenton reaction is 2.0?3.0,so the pH of the effluent from 001×7H resin treatment is directly underwent glow discharge/Fenton oxidation after slight pH adjustment,and then passed through the 201 resin,which can greatly reduce the amount of chemicalsfor pH adjustment required by the Fenton reaction.The optimized route is AS coagulation-001×7H resin adsorption-glow discharge/Fenton oxidation-201 resin adsorption,where the COD of effluent from glow discharge/Fenton oxidation is 763 mg/L and NH3-N was increased from 208 mg/L to 256 mg/L.COD and NH3-N can be further reduced to 87 mg/L and 221 mg/L with the adsorption of 201 resin,where COD achieves the first-level standard of the Sewage Comprehensive Discharge Standard(GB8978-1996).The cost of the chemicals in the combined process to treat 1 m3 of wastewater is 64.75 RMB,and the cost of electricity is 123.75 RMB,which has certain advantages over other competitive processes.(4)In order to take the removal of NH3-N into account,we investigate the effect of electrolysis on the treatment of wastewater after coagulation treatment.In order to improve the efficiency of electrolysis,AS,H2SO4 and AC were mixed together as the coagulant.Under applied voltage of 3.0 V and current of 1.0 A,where the current density is 25 A/m2,the concentration of NH3-N can be lowered to below 15 mg/L with 8 h of electrolysis.The electrolytic efficiency dropped significantly after 9 h.COD and NH3-N can be lowered to 2530 mg/L and 204 mg/L after 6 h of electrolysis,and they continued to be reduced to 1630 mg/L and 4 mg/L after 12 h of electrolysis,where NH3-N achieves the first-level standard of the Sewage Comprehensive Discharge Standard(GB8978-1996).After 12 h of electrolysis,ion exchange resin was used for the subsequent treatment.COD of the effluent from 001×7H resin and 201 resin was lowered to 558 mg/L.The cost of chemicals required to treat 1 m3 of wastewater is 37.42 RMB,and the cost of electricity is 41.25 RMB.