Study On Degradation Of Organic Pollutants In Salty Wastewater From Coal Chemical Industry By Heterogeneous Catalytic Ozonation

"Near zero discharge" of salty wastewater from coal chemical industry is the development goal of modern coal chemical industry.At present,the most economical and efficient technology for treating salty wastewater in coal chemical industry is evaporation and crystallization.However,the organic pollutants in the wastewater are important factors that affect the evaporation and crystallization.Organic matter will affect the quality of crystalline salt,making it unable to meet the industrial recycling standards,and will eventually be treated as solid waste,causing environmental pollution and resource waste.Therefore,the treatment of organic matter in the salt-containing wastewater of coal chemical industry is of great significance to the realization of the goal of "near zero discharge".This paper takes the salty wastewater from the Ningdong Coal Chemical Industry Base in Ningxia as the research object,and uses coagulation precipitation pretreatment and catalytic ozone oxidation advanced treatment technology to remove organic pollutants in the wastewater.The main research contents and results are as follows:(1)Coagulation and sedimentation process was used to coagulate the colloids and some fine suspended solids in the salt-containing wastewater of coal chemical industry.The removal of chemical oxygen demand(COD)and chromaticity of wastewater by four coagulants of polyferric sulfate(PFS),polyaluminum chloride(PAC),polyaluminum ferric chloride(PAFC),and acrylamide(PAM)were investigated.The results show that PAFC has the best treatment effect.Under the condition of 600 mg/L and 2 hours of operation,the COD concentration of the effluent is reduced from 786 mg/L to 580 mg/L,and the chromaticity is reduced by 375 times.To 208 times,the removal rate of COD and color reached 26.5%and 44.6%,respectively.(2)The Mn-Cu-Ce/Al2O3 supported multi-metal oxide catalyst was prepared by the impregnation-calcination method,and it was applied to the research of catalytic ozonation and degradation of organic pollutants in salt-containing wastewater of coal chemical industry.The catalyst characterization and performance test results show that the catalyst has good dispersibility,and the synergy between the metal oxides greatly enriches the catalytic active sites and enhances the performance of catalytic ozone oxidation.Compared with ozone oxidation alone(39.6%),Mn-CuCeAl2O3 catalytic ozone oxidation has a 70.2%removal rate of wastewater TOC,which is an increase of 30.6 percentage points.After catalytic ozone oxidation,the COD,total organic carbon(TOC),and chromaticity of wastewater are reduced from the initial 580mg/L,168.2 mg/L,and 375 times to 105 mg/L,65.3 mg/L,and 25 times,respectively.Five-day biochemical The oxygen demand(BOD5)increased from 1.7 mg/L to 29.5 mg/L,the value of BOD5/COD increased from 0.003 to 0.320,and the biodegradability was significantly improved,the ketones,aromatic hydrocarbons,phenols and nitrogencontaining heterocyclic compounds in the wastewater have been effectively degraded and mineralized.the catalyst showed good stability and repeatability.in six consecutive uses.(3)The Co3O4-C composite material was prepared by calcining metal organic framework(MOF)ZIF-67,which was used as a high-efficiency catalyst for the degradation of simulated acetone wastewater by catalytic ozonation.The catalyst characterization results show that C03O4-C maintains a polyhedral structure and morphology similar to ZIF-67,and Co3O4 is evenly distributed in C03O4-C,and a large number of carbon and oxygen functional groups are distributed on the surface of the catalyst,which makes the catalytic reaction active center diversified.Compared with ozone oxidation alone(23%),C03O4-C catalytic ozonation(48%)improves the TOC removal rate of wastewater by 24%.The mechanism of Co3O4-C catalyzing the oxidation of ozone is to promote the hydroxyl radical(·OH),which shows good stability in 5 consecutive cycles.(4)The GO-CoFe2O4 composite material was synthesized by the co-precipitation method,and it was applied to the study of the degradation of simulated benzotriazole wastewater by catalytic ozonation.The results show that the prepared GO-CoFe2O4 has a larger surface area than CoFe2O4,and the CoFe2O4 grown on the GO sheet is evenly distributed.The doping of GO makes the catalyst distribute a variety of surface functional groups,which enriches the active sites for the catalytic reaction,improved the ozone decomposition and oxidation ability.Under the conditions of catalyst dosage of 1 g/L,ozone concentration of 15 mg/L,and reaction time of 60 min,the TOC of wastewater can be reduced from 375 to 45 mg/L,with a removal rate of 88%.Compared with ozone alone,the TOC removal rate is increased by 28%,showing a good catalytic effect.In addition,the unique magnetic properties of the catalyst material facilitate further recycling after the reaction.