| This study is set to investigate the adsorption/desorption characteristics of hexachlorobiphenyl PCB138 on soils,organic matter extracts and factors influencing on them.Red soil and black soil with high organic matter content were selected as test soil to extract humic acid and humin from soil organic matter components.Oscillating equilibrium method was used.The adsorption/desorption characteristics of PCB138 in soil,humic acid and humin were studied from both kinetic and thermodynamic aspects.The results show that the adsorption/desorption of PCB138 in two soils and their organic matter components is a fast process.The adsorption equilibrium can be reached in 240 minutes and desorption equilibrium can be reached in 360 minutes.The adsorption rate and adsorption capacity are in the order of humic acid>native soil>humin from large to small,and the desorption rate is in the order of Humin>native soil>humic acid,and the Quasi-First-Order kinetic equation is better.In the two soils tested,the adsorption rate and amount of PCB138 in black soil were slightly higher than those in red soil,while the desorption rate and amount were the opposite,indicating that the stronger the adsorption capacity of PCB138,the weaker the desorption capacity.The adsorption/desorption isotherm can be described by Freundlich adsorption isotherm equation,and the comparison of thermodynamic parameters such as?G~0,?H~0 and?S~0shows that the adsorption of PCB138 in two soils belongs to physical adsorption,which is a process of non-spontaneous,endothermic and systematic disorder increase,while the desorption process is a process of non-spontaneous,exothermic and systematic disorder decrease.Pearson correlation analysis showed that the adsorption/desorption of PCB138 was mainly affected by the content of organic matter in soil physical and chemical properties.The adsorption/desorption process of PCB138 in soil lags behind,and adsorption and desorption are two irreversible processes. |
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