Study On Adsorption-desorption Properties Of PAHs By Biochar With Different Pyrolysis Temperatures

PAHs is the product of incomplete combustion of fossil fuels or pyrolysis of other organic matter.Most PAHs have strong carcinogenic,teratogenic and mutagenic effects.It is widely believed that the main sources of PAHs in the environment are human activities,especially the burning of mineral fuels.Although PAHs can be detected in atmospheric particulate matter,water and soil,the main aggregation site in terrestrial ecosystems remains soil.This study by corn straw as raw material,preparation of biochar in 400 ~ 700 ?,choose Phe and Pyr as the research object,research different pyrolysis temperature on the physicochemical properties of biochar,preparation of temperature at four different biochar for two kinds of pahs in different contact time,adsorption and desorption behavior of concentration of pollution,in order to living material resource and screening effective biological carbon in pahs governance provide theoretical basis for the application.Meanwhile,in the next stage of this project,the PAHs in soil was prepared by using biochar as the immobilized carrier of biodegradable bacteria.In this study,the physical and chemical properties of biochar were studied with the changes of the raw materials and pyrolysis temperature,and the adsorption and desorption behavior of these biochar on pyrene and benzene were studied.The physical and chemical properties of biochar as the pyrolysis temperature had obvious changes.With the temperature increasing of pyrolysis,carbonization degree is bigger,the yield is lower and higher ash content,specific surface area is larger and less number of polar functional groups,higher aromaticity,stronger hydrophobicity,pore structure is more developed.Through fitting of adsorption kinetics model,found that the adsorption effect of biochar on phenanthrene,pyrene tend to chemical adsorption,rather than the physical adsorption,and adsorption under the influence of particle diffusion process inside the control factors but not the only one.Biochar prepared at different pyrolysis temperatures,with the same treatment time,the biochar increases with the firing temperature,and the adsorption capacity of Phe and Pyr in the solution is continuously enhanced.The adsorption capacity of biochar on Phe is greater than Pyr,because the smaller pyrene molecules are more likely to reach the adsorption point.The adsorption/desorption isotherm of biochar to Phe and Pyr was non-linear.Freundlich model nonlinear index n value decreases with biochar pyrolysis temperatures,show that nonlinear degree increases with temperature rise,may be the main adsorption mechanism by the distribution of biochar into surface adsorption,the pore intercept.