Sorption Behavior Of Phenanthrene And Pyrene On Humic Acid And Black Carbon Extracted From River Sediments

Polycyclic aromatic hydrocarbons?PAHs?are a class of persistent organic pollutants that are ubiquitous in environmental media.Its adsorption behavior on river sediments,especially on organic matter,directly affects its environmental fate and human health.Humic acid?HA?and black carbon?BC?are the main components of sediment organic matter?SOM?in river water,which are the key factors affecting the adsorption behavior of pollutants in sediments and water bodies.By studying the adsorption behavior of typical organic pollutants-PAHs on HA and BC,it is helpful to understand and grasp the adsorption regularity of PAHs on SOM and explain the adsorption mechanism.In this paper,two typical organic matters-HA and BC extracted from river sediments are selected as adsorbents for pollutants.Polycyclic aromatic hydrocarbons represented by phenanthrene?phe?and pyrene?pyr?are used as target pollutants.The adsorption behavior of PAHs on HA and BC was studied by static adsorption method,mainly including the determination of partition coefficient,the study of adsorption isotherms and the effect of calcium ion(Ca²⁺)concentration and organic carbon content of adsorbent on adsorption.At the same time,the elemental composition,organic carbon content,specific surface area and pore size,functional group composition,morphology and surface charge of HA and BC were analyzed by elemental analyzer,total organic carbon analyzer?TOC?,specific surface area and pore analyzer,Fourier transform infrared spectroscopy?FTIR?,scanning electron microscope?SEM?,Zeta potential meter and X-ray diffractometer?XRD?.The main findings of this study are as follows:?1?Through characterization analysis,the main sources of HA and BC are aquatic plants,whose main components are carbon and oxygen.Both are complex organic compounds containing aromatic carbon and fatty carbon,and are rich in oxygen-containing functional groups such as phenolic hydroxyl group,alcoholic hydroxyl group and carboxyl group.Black carbon has a microporous structure.Its pores are larger,and the surface has less negative charge under neutral conditions.The organic carbon content of BC is much higher than that of HA.?2?The logarithm of the distribution coefficients?Log K_d?of phe and pyr on HA are 3.55 and 4.40,respectively,and the logarithm of the organic carbon normalized distribution coefficients(Log K_oc)are 4.34 and 5.18,respectively.The hydrophobic pyr is more readily adsorbed on HA and BC than phe.The adsorption capacity of BC for phe and pyr is several times higher than that of HA,which is related to the microporous structure,the small inter-molecular repulsion and high organic carbon content of BC.And the organic carbon content of the adsorbent has an important influence on the adsorption capacity.?3?The adsorption isotherms of phe and pyr on the two organic matters are nonlinear.And under three temperature conditions,the adsorption amount of phe and pyr on the HA and BC at adsorption equilibrium increases with the increase of equilibrium concentration.?4?The adsorption amount of phe and pyr on HA and BC showed a trend of increasing first and then decreasing with the increase of Ca²⁺concentration.The adsorption capacity of phe on HA and BC reaches the maximum when the Ca²⁺concentration is 0.05 mol/L,which is 56.9?g/g and 118?g/g,respectively.And the adsorption capacity of pyr on HA and BC reaches the maximum when the Ca²⁺concentration is 0.01 mol/L,which is 122?g/g and 139?g/g,respectively.