CTMA-蒙脱石吸附苯分子的分子动力学模拟研究

Molecular Dynamic Simulation of Benzene Molecules Adsorption in CTMA-Montmorillonite

有机粘土对疏水性有机污染物吸附性能良好,在环境有机污染控制中有广阔的应用前景。明确有机污染物在有机粘土上吸附的微观结构特征是探明其吸附机理,提高其污染控制效率的关键。论文以十六烷基三甲基铵阳离子改性蒙脱石(CTMA-Mont)为有机粘土代表,采用分子动力学模拟技术,模拟研究了水环境条件下CTMA-蒙脱石对典型疏水性有机污染物苯的吸附特征,得到了CTMA-Mont层间域内原子尺度微观结构。研究发现苯分子主要吸附在CTMA烷基链聚集体内,而蒙脱石硅氧烷表面由于受到烷基链的竞争而对苯分子的吸附能力较弱。随着CTMA负载量的增加,层间域内烷基链聚集体的体积增大,因而能为苯分子提供更多的吸附位点,CTMA-Mont吸附性能相应增强。

Numerous studies have shown that organoclays can effectively adsorb hydrophobic organic contaminants and they have been considered as efficient adsorbents for the remediation of organic pollution. Understanding the adsorptive characteristics of organoclays is critical for improving their remediation efficiency. In this work, cetyltrimethylammonium cation modified montmorillonite(CTMA-Mont) was selected as a representative organoclay, and its adsorptive characteristics towards benzene molecules were studied using molecular dynamic(MD) simulations. Our results show atomic-level structure of the interlayer spaces of the water saturated CTMA-Mont. Benzene molecules were found to be adsorbed primarily in the alkyl-chain aggregates of CTMA; while a hydrophobic siloxane surface could not effectively adsorb benzene molecules because of the strong competition effect from alkyl chains. With increasing CTMA load level, the size of alkyl-chain aggregates increase accordingly, and they can provide more adsorption sites for benzene molecules, which then finally leads to enhanced sorption of benzene molecules in CTMA-Mont.