Effect of SDBS of different mass fractions on coal's wettability by molecular simulation

In order to study effects of surfactant on coal ' s wettabilityꎬ with SDBS taken as research objectꎬ Wiser coal chemical structure model and Material Studio molecular simulation software were used to establish a system where SDBS of six different mass fractions coexisted with water and coal. Thenꎬ the system' s adsorption configurationꎬ energy changesꎬ relative concentration distribution as well as mean square displacement (MSD) of water molecules were analyzed. The results show that hydrophobic alkyl chains of SDBS molecules are adsorbed on coal surfaceꎬ and hydrophilic group with benzene ring warps to water phaseꎬ which reduces liquid ̄solid interfacial tension of water and coal. As mass fraction of SDBS 中 国 安 全 科 学 学 报 China Safety Science Journal 第30卷 2020年 increasesꎬ the system's total energy decreasesꎬ but interaction energy between SDBS and coal increasesꎬ indicating that adsorption between molecules is more stable and wettability is enhanced. Spatial distribution difference of hydrophobic alkyl chains of SDBS molecules is one of the main factors affecting wettability. Diffusion coefficient of water molecules increases along with the growth of SDBS mass fractionꎬ which has a significant effect on wettability of coal.