Adsorption/Desorption Characteristics Research Of Dibutyl Phthalate On Two Farmland Soils In Jilin Province

As a plasticizer,Phthalic Acid Esters?PAEs?are widely used in the production of various plastic products.In recent years,with the use of the agricultural plastic film,they bring economic benefits to agriculture,but also inevitably bring environmental pollution problems.PAEs can leak from plastic mulch film to enter the soil environment and remain stable for a long time,which can threaten the normal endocrine function of the human body and animals through the food chain.In this study,Dibutyl phthalate?DBP?which is the priority controlled pollutant of PAEs,was selected as the test pollutant.Planosol and Black soil which are two typical farmland soils in Jilin Province,were selected as the test soil.In order to study the adsorption and desorption characteristics of DBP in Planosol and Black soil,and the effects of different influencing factors on their adsorption and desorption characteristics.The main results were summarized as follows:?1?The process of DBP adsorption/desorption in Planosol and Black soil all could be divided into three stage:rapid adsorption/desorption,slow adsorption/desorption and equilibrium adsorption/desorption.The time of adsorption equilibrium was about24 hours and the time of desorption equilibrium was about 16 hours.When the process of desorption attain equilibrium,the desorpted quantity were accounted on 15.64%and37.06%of equilibrium adsorption quantity respectively in the Planosol and Black soil.The pseudo-second-order kinetic equation,the Elovich equation,particle diffusion equation,and the double constant equation all could describe adsorption kinetics well.The correlation coefficient was significant?p<0.05?.?2?Freundlich model and Henry model could fit the isothermal adsorption/desorption process of DBP in Planosol and Black soil well.The correlation coefficient was extreme significant?p<0.01?.The fitting results showed that the adosorption ability of DBP in the Planosol was greater than Black soil.The average Hysteresis index?HI?in two kinds soil were both less than 0.7,which could illustrate hysteresis phenomenon was estence in the desorption progress.?3?Equilibrium adsorption quantity increased and equilibrium desorption quantity decreased in the Planosol and Black soil when the test temperature increased.The?G values of DBP in Planosol and Black soil at three kinds of temperature were all less than 0,Absolute value less than 40kJ·mol^-1 as well as the values of?S and?H were all greater than 0,it indicted that the adsorption progress of DBP in two soils belonged to spontaneous and endothermic process with entropy increase.?4?Regardless of Mg²⁺,the higher the valance state of cations,the greater positive charge and the ability to compete for adsorption sites with DBP was stronger,Equilibrium adsorption quantity of DBP was lower,equilibrium desorption quantity was higher.The increase of cationic concentration was beneficial to adsorption of DBP in Planosol and Black soil but was not conducive to desorption.After removing organic matter,the equilibrium adsorption capacity of DBP on soil decreased,and the addition of organic matter could promote the adsorption of DBP on both soils.The higher the pH,the lower the equilibrium adsorption and the higher desorption of DBP in the two soils,which indicated that the acidic environment was conducive to the accumulation of DBP in the soil,and the alkaline environment was conducive to the release of DBP from the soil and migration to the outside environment.