Abstract: In order to study effects of surfactant on coal's wettability, with SDBS taken as research object, 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. Then, the system's adsorption configuration, energy changes, 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 surface, and hydrophilic group with benzene ring warps to water phase, which reduces liquid-solid interfacial tension of water and coal. As mass fraction of SDBS increases, the system's total energy decreases, but interaction energy between SDBS and coal increases, 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 fraction, which has a significant effect on wettability of coal.

Key words: sodium dodecyl benzene sulfonate (SDBS), coal's wettability, molecular dynamics, adsorption configuration, relative concentration distribution