Study On Mechanism Of Organic Matter In Coal Pyrolysis Wastewater Adsorbed By Carbon Adsorbent

The cascade utilization of low-rank coal is one of the important development directions of coal chemical industry.Henan Longcheng Group has developed the low-rank coal rotating bed lowtemperature dry distillate quality utilization technology,and built an annual processing 10 million tons of low-rank coal in Caofeidian,Hebei.However,after the plant was put into operation,the problem of difficult treatment of pyrolysis wastewater appeared.Although membrane separation,coagulation sedimentation,advanced oxidation and other methods have been tested successively,the problems have not been completely solved.This paper takes the wastewater as the research object,and carries out the related basic and application research on its treatment by adsorption method.This paper studies the basic characteristics of four kinds of carbonaceous adsorbents and coal pyrolysis water,and explores the adsorption laws of the four adsorbents on organic matter in coal pyrolysis water.Through characterization methods such as SEM,BET,FT-IR,EDS,XPS,and industrial analysis,the correlation between the physical and chemical properties of the adsorbent and the adsorption of coal pyrolysis wastewater was studied,and the adsorbents with similar surface element composition and carbon elements were obtained.Combined form,but the specific surface area,average pore size,industrial analysis and other parameters have obvious differences.Through sequential batch experiments,the influence of the dosage,adsorption time,pH value,initial concentration and other factors on the adsorption of coal pyrolysis water was studied,and it was obtained that within a certain range,the greater the dosage of adsorbent,the longer the adsorption time The longer,the smaller the pH,and the larger the initial concentration,the better the removal effect of COD in the water sample.This paper explored the adsorption performance characteristics of different carbon adsorbents for different components in coal pyrolysis wastewater.Through the analysis of GC-MS,UV254,conductivity,TDS and salinity and other indicators,it is found that there are 142 types of benzene and benzene derivatives,macromolecular acids,nitrogen-containing heterocyclic compounds,long-chain hydrocarbons,and other five types in the wastewater.Benzene and benzene derivatives accounted for the largest proportion,reaching 82.9%.The four carbon adsorbents have a good adsorption effect on benzene and benzene derivatives,and the removal rate is above 78%.The adsorption effect on nitrogen-containing heterocyclic compounds is slightly worse,the highest removal rate is only about 47%.There is almost no adsorption of macromolecular acids and inorganic ions Commercial activated carbon and lignite pulverized coke are far more effective in removing long-chain hydrocarbons than unshaped activated coke.Brown coal pulverized coke is not effective in removing unsaturated aromatic compounds,and the removal rate is only 8.5%.Combined with the experimental data,this paper theoretically analyzes the adsorption kinetics and thermodynamics of the adsorbent on the organic matter,and found that the adsorption kinetics of the four adsorbents on the pollutants can be described by a pseudo-two-stage kinetic model,and the adsorption rate is jointly controlled by the intra-particle diffusion process and the liquid film diffusion process.The Langmuir isotherm adsorption model can better describe the adsorption behavior of organic matter on the adsorbent,which proves that the adsorption process is dominated by monolayer adsorption.In the adsorption process,the thermodynamic functions ΔGo,ΔSo and ΔHo are all negative values,which proves that the process is a spontaneous,entropy reduction,and exothermic process,and physical adsorption is dominant.