Study On High Efficient Treatment Process Of Soluble Organic Substances In Coking Wastewater

Coking wastewater mainly comes from coal coking,coal gasification,refined benzene production,by-product recovery and other technological processes,which is a complex mixture of hazardous and toxic organic compounds,with high concentration of phenol,cyanide,thiocyanate,polycyclic aromatic hydrocarbons,heterocyclic compounds and ammonia nitrogen.Most of these compounds are hard to be degraded.At present,the treatment methods of coking wastewater mainly include physical,biological and chemical methods.However,there are many bottleneck problems in these methods.In order to seek a new breakthrough in coking wastewater treatment,based on the analysis of the components of the soluble organic matter in coking wastewater,phenolic condensation,ozonation and catalytic hydrogenation were used to treat the soluble organic matter in coking wastewater,the research contents and conclusions are as follows:(1)The dissolved organics in coking wastewater samples were separated by Amberlite XAD-8 resins.According to the different kinds of eluent,the organics were divided into four categories:hydrophobic acids(HOA),hydrophobic bases(HOB),hydrophobic neutrals(HON)and hydrophilic substances(HIS).There are 123 kinds of organic compounds in coking wastewater.The results show that main components of HIS are organic acids,alcohols and crown ethers and HOA mainly contains organic acids and phenolic compounds.The composition of HOB mainly includes many kinds of amines and nitrogen-containing heterocyclic compounds.For HON,esters account for the majority and polycyclic aromatic hydrocarbons occupy a part.(2)The aldol condensation followed by ozonation method was applied to reduce the phenolic compounds in coking wastewater.The influences of several operation parameters including the molar ratio of formaldehyde to phenol(F/P),pH value,reaction temperature and reaction time were investigated,which suggested that increasing F/P,pH value,reaction temperature and time markedly promoted the condensation reaction conversion.Under the proper conditions the aldol condensation reduced the concentration of phenolic compounds from 9018 mg/L to 764.7 mg/L,after which the ozonation treatment further reduced the concentration of phenolic compounds to 22 mg/L,resulting in total removal efficiency of 99.8%.After the step of phenolic compounds reduction,the COD value of coking wastewater is reduced from 71400 mg/L to 18250 mg/L.(3)A series of nickel-based catalyst was synthesized by the bulk method during the crystallization process of Y zeolite.They were characterized by XRF,XRD,TEM,N2 physical adsorption and desorption,NH3-TPD,Py-IR and XPS.It was proved that the highest Ni content of the synthesized catalyst was 21.4wt%,with high specific surface area and good dispersion of Ni species.With the increase of Ni content,the acid content of the catalyst increased.The synthesis catalysts combined with HZSM-5zeolite were used to treat the soluble organic matter in coking wastewater by catalytic hydrogenation.The effects of catalyst type,catalyst dosage,reaction temperature and reaction time on the reduction of COD in coking wastewater were investigated.The results showed that when the reaction pressure was 3 MPa,reaction time was 4 hours,reaction temperature was 300 ~oC,and 0.5 wt.%nickel-based catalyst with the content of nickel is 21.4 wt.%accompanied by 2 wt.%ZSM-5 were added,the removal efficiency of COD is the best,the COD value reduced from 18250 mg/L to 8350 mg/L,and the removal efficiency is 54.7 wt.%.