SDBS溶液对赵庄煤表面润湿作用机理的研究

Study of the wetting mechanism of SDBS solution on Zhaozhuang coal surface

采用原子力显微镜(AFM)实验研究了十二烷基苯磺酸钠(SDBS)溶液浓度对赵庄煤表面水化膜厚度的影响规律,基于赵庄煤-SDBS-水三相动力学模型,从分子尺度揭示了SDBS溶液对煤表面的润湿机理.结果表明:随着SDBS溶液浓度的增加,赵庄煤表面水化膜厚度呈现先增加后减小的变化规律,当SDBS溶液质量分数为0.050%时,煤表面水化膜厚度达到最大值13.7 nm,分子模拟结果表现出与实验相同的变化规律,验证了模拟的合理性.结合表面活性剂吸附构型图和径向分布函数(RDF)分析结果,揭示了SDBS分子中疏水尾部垂直于煤分子表面,亲水头部伸向水中的取向问题.通过RDF分析得出SDBS分子最容易吸附在赵庄煤分子中由多个苯环构成的芳香环上,且苯环的中间位置是最佳吸附位点(C吸附位点).当表面活性剂分子个数逐渐增多时,SDBS分子尾部与C吸附位点之间的距离先减小后增大,与实验所得水化膜厚度变化趋势相同.

The atomic force microscope (AFM) experiment was used to study the influence law of different concentrations of sodium dodecyl benzene sulfonate (SDBS) solution on the thickness of hydration shell on the surface of Zhaozhuang coal, and the wetting mechanism of SDBS solution on Zhaozhuang coal surface was revealed from the molecular scale based on Zhaozhuang coal-SDBS-water three-phase dynamic model. The results show that, with the increase of SDBS solution concentration, the thickness of hydration shell on the surface of Zhaozhuang coal increases first and then decreases. When the concentration of SDBS solution is 0.050%, the maximum of hydration shell is 13.7 nm. The result of molecular simulation shows the same change law as that of experiment, which verifies the rationality of simulation. Combined with the surfactant adsorption configuration diagram and the analysis results of radial distribution function, the orientation of hydrophobic tail perpendicular to the surface of Zhaozhuang coal molecules and hydrophilic head towards water in SDBS molecules is explained in this paper. It is concluded that SDBS molecules most easily adsorb on aromatic rings composed of multiple benzene rings in Zhaozhuang coal molecules through RDF analysis, and the enter site of the benzene ring is the best adsorption site (C adsorption site). With the number of surfactant molecules increasing, the distance between the tail of SDBS molecule and the C adsorption site decreases first and then increases, which is the same as the changing trend of the thickness of hydration shell.