分子模拟多溴联苯醚在石英砂纳米孔中的吸附行为

Molecular dynamic simulation of adsorption of polybrominated diphenyl ethers in silica nanopores

多溴联苯醚(PBDE)是一种广泛使用的阻燃剂,也是普遍关注的持久性有机污染物之一。利用分子模拟手段建立5种低溴代PBDE分子(BDE-28、BDE-47、BDE-77、BDE-99、BDE-153)在石英砂纳米孔(2.0nm、2.5nm、3.0nm、3.5nm)中的吸附模型,利用孔径变化模拟土壤的物理老化过程,并研究土壤有机质(SOM)对PBDE吸附能与均方位移(MSD)的影响。结果表明,孔径的缩小降低了体系的总势能和非键能,使其体系更加稳定;然而PBDE与石英砂之间的吸附能随孔径的缩小而增大,且该吸附能以范德华力为主,占体系吸附能的84.0%。SOM的加入则导致体系的总势能和非键能以及PBDE与石英砂之间的吸附能均降低,虽然与石英砂孔内表面的吸附能降低有利于PBDE分子的迁移,但由于SOM与PBDE之间的吸附作用占主导,抑制了PBDE在纳米孔中的扩散,因此PBDE的MSD值反而降低。

Polybrominated diphenyl ethers （PBDEs） are widely used flame retardants,which have become one branch of persistent organic pollutants with worldwide concern. In order to investigate adsorption of PBDEs in silica nanopores,molecular dynamic simulations were performed for five PBDEs,including BDE-28,BDE-47,BDE-77,BDE-99 and BDE-153 in silica nanopores with respective apertures of 2.0nm,2.5nm,3.0nm and 3.5nm. The system energy declined with the decrease in aperture,but an opposite tendency was observed for the adsorption energy between PBDEs and silica nanopores. The adsorption energy was dominated by van der Waals force which accounted for 84.0% of the overall adsorption energy. The mean square displacement （MSD） values for PBDEs in the silica nanopores decreased with the increase of adsorption energy. Additionally,the presence of soil organic matter （SOM） decreased the system energy and the adsorption energy between PBDEs and silica nanopores. The decrease of adsorption energy might favor PBDEs diffusion in nanopores, however,the MSD values for PBDEs were reduced since interaction between PBDEs and SOM seriously affected PBDEs diffusion properties.