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SDS/SDBS对无烟煤润湿性影响的分子动力学模拟

Molecular dynamics simulation of the effect of SDS / SDBS on the wettability of anthracite

  • 摘要: 为了探究阴离子表面活性剂在煤矿除尘中的微观作用机理,采用分子动力学模拟方法,选取2种常用阴离子表面活性剂十二烷基硫酸钠(SDS)与十二烷基苯磺酸钠(SDBS),研究其对无烟煤润湿性的影响。计算了表面活性剂–无烟煤吸附体系的表面粗糙度和相互作用能,分析了水–表面活性剂–无烟煤体系的相对浓度分布、径向分布函数(RDF)等系列性质,深入探讨无烟煤润湿性改变的微观原因。结果表明:阴离子表面活性剂在无烟煤上的吸附有2种方式,头基团朝向无烟煤表面的吸附与朝向液相的吸附;这种吸附是物理吸附,且范德华相互作用在吸附过程中起主导作用;SDBS中苯环的存在导致其更紧密的吸附在无烟煤表面,吸附构型更稳定。RDF与配位数结果进一步表明,在无烟煤表面酮基附近SDS与SDBS疏水能力相近;在羟基附近SDBS疏水能力强于SDS,这是SDBS吸附后无烟煤疏水性更强、润湿性改变程度更大的主要原因;苯环在无烟煤润湿性改变中起重要作用。这为煤矿除尘中表面活性剂的选取,提供了一定的依据,丰富和发展了无烟煤润湿性基础理论。对这2种阴离子表面活性剂的吸附行为和润湿性变化的分子动力学模拟评价与已有试验数据吻合较好。

     

    Abstract: In order to explore the microscopic mechanism of anionic surfactants in coal mine dust removal. Using molecular dynamics simulation methods, two commonly used anionic surfactants, sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS), were selected to study their effects on the wettability of anthracite. The surface roughness and interaction energy of the surfactant anthracite adsorption system were calculated. The relative concentration distribution and radial distribution function (RDF) of the water surfactant anthracite system were analyzed. The microscopic reasons for the wettability change of anthracite were discussed.The results show that there are two ways of adsorption of anionic surfactants on anthracite, the adsorption of the head group toward the surface of the anthracite and the adsorption toward the liquid phase; this adsorption is physical adsorption, and van der Waals interaction plays a leading role in the adsorption process; The presence of benzene ring in SDBS leads to tighter adsorption on the surface of anthracite, and the adsorption configuration is more stable. The results of RDF and coordination number further show that the hydrophobicity of SDS near the ketone group of anthracite is similar to that of SDBS; the hydrophobicity of SDBS near the hydroxyl group is stronger than that of SDS, which is the main reason for the stronger hydrophobicity and greater wettability change of anthracite after adsorption by SDBS; Benzene ring plays an important role in the change of wettability of anthracite. This provides a certain basis for the selection of surfactants in coal mine dust removal. The basic theory of wettability of anthracite has been enriched and developed. The molecular dynamics simulation evaluation of the adsorption behavior and wettability changes of these two anionic surfactants is in good agreement with the existing experimental data.

     

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