分子模拟十六烷基三甲基溴化铵对石油污染物在粗糙石英砂表面脱附的影响

Molecular dynamic simulation of oil pollutants desorption from rough quartz sand surface by CTAB extraction

溶剂萃取法广泛应用于石油污染土壤的修复,萃取前后土壤微观结构的改变会影响石油污染物在土壤中的迁移和传递。本文利用分子动力学模拟方法,通过在石英砂表面上构造不同的凹槽代表矿物表面粗糙的结构,研究十六烷基三甲基溴化铵(CTAB)水溶液萃取石油污染物(正十二烷)的过程。结果表明:(1)脱附过程的主要驱动力为凹槽外的正十二烷和CTAB分子与凹槽内正十二烷分子之间的相互作用;(2)凹槽的宽度减小或者凹槽的深度增加,均会增加槽内正十二烷分子的脱附难度,同时还会影响CTAB分子的促进脱附效果;(3)CTAB分子对石油脱附的促进效果随其浓度的增加而减弱,当持续增加体系中CTAB的含量时(不同模拟体系中的CTAB分子数量分别为0、16、32),会抑制其促进脱附的效果。

Solvent extraction is widely used in the restoration of oil contaminated soil,and the changes of soil microstructure before and after extraction will further affect the migration and transfer of oil pollutants in soil.Using molecular dynamics simulation method,this paper researched oil pollutants(n-dodecane)detachment in hexadecyl trimethyl ammonium bromide(CTAB)aqueous solution from quartz sand surface.Grooves with different widths or depths were constructed on quartz sand surface,which represented the mineral surface coarse structure.The results showed that:①the main driving factors of the desorption process of the n-dodecane molecules in grooves are the CTAB molecules and the n-dodecane polymer outside grooves;②Reduction of the width of grooves or increase of the depth of grooves inhibit the desorption of n-dodecane molecules,and also restrain CTAB molecules from promoting the removal of oil;③The concentration of CTAB is not proportional to the percentage of desorpted n-dodecane molecules.The system containing 16 CTAB molecules may achieve a better degree of n-dodecane molecules detachment than the systems containing 0 or 32 CTAB molecules.