| Polybrominated diphenyl ethers (PBDEs) have been extensively used as flame retardants in industries. Recently, PBDEs have been detected in various environmental compartments, due to its high bioaccumulation effect and endocrine disturbance characteristics, it is necessary to master the transformation and migration pathways of PBDEs in the environment.2,2’,4,4’-tetrabromodiphenyl ether (BDE-47) and 2,2’,4,4’,5-pentabromodiphenyl ether (BDE-99) have been world-wide pollution,in this study, sorption and desorption behaviors of BDE-47 and BDE-99 on soil components and biochar samples were discussed,and the effect of biochar addition amount and temperature on soption and desorption behaviours of BDE-99 in natural soil were demonstrated.Comparison of biochar properities demonstrated that with pyrolysis temperature increased, the process of organic matter condensation and aromatization was accelerated, the internal porous structures developed and microporous structure increased.For BC300 and BC500, the mesopores and micropores were the main pore structure; For BC700, micropores were the main pore structure.Two-compartment first-order model was more appropriate for the sorption kinetics, which showed the fast sorption dominated the sorption progress. The sorption process of BDE-47/BDE-99 on biochar and soil samples was spontaneous. Adsorption of BDE-47/BDE-99 on biochar samples was nonlinear, adsoption capacity was in the order:BC700>BC500>BC300. For BC300 and BC500, pore-filling adsoption and surface adsoption involved in the adsorption process; for BC700, pore-filling adsoption dominated the adsorption process. BDE-47/BDE-99 desorption hysteresis from BC300, BC500 was similar, while BC700 was most significant, it’s mainly because BC700 can provide more high energy adsorption sites.Adsorption of BDE-99 on soil samples was nonlinear. With the initial concentration increased, K∞ value of three soil samples decreased. Organic matter content of soil samples was the main influencing factor on BDE-99 sorption process. BDE-99 desorption hysteresis existed in the soil samples, compared with biochar samples, its variation was not obvious, it may because there is no significantly distinguish between high energy adsorption sites and low-energy adsorption sites on soil samples.Biochar added content and environment temperature had significant impact on adsorption and desorption behavior of BDE-99 on soil system. Addition of biochar to soil samples enhanced the adsorption ability of BDE-99 on soil samples, while the degree of nonlinear adsorption and desorption hysteresis significantly increased. Environment temperature increased from 10℃ to 35℃, desorption hysteresis of BDE-99 on biochar mixed soil weakened. |
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