Effect of anionic/nonionic surfactants on the wettability of coal surface

To study the effect of different surfactants on the wettability of coal surface, the adsorption simulation of different coal-surfactant-water model systems was carried out by using materials Studio 8.0 molecular simulation software. Combined with the contact angle experiments between different surfactants and coal samples, the effect law of different surfactants on the wettability of three coal samples was obtained. The adsorption simulation results were analyzed from the aspects of adsorption spacing, adsorption sites and “reverse adsorption” phenomenon, and the mechanism of the influence of different surfactants on the wettability of coal surface was revealed from a microscopic point of view. The research results show that: the higher the degree of coal metamorphism, the lower the water absorption and the worse the wettability of coal. Anionic surfactant SDBS has better effect on improving the wettability of Hami (HM) coal with low metamorphic degree, while nonionic surfactant AEO9 has better effect on improving the wettability of Yuwu (YW) and Tunliu (TL) coal with high metamorphic degree. By comparing intermolecular distances, it is shown that nonionic surfactants are more likely to aggregate on the surface of coal molecules and have a greater effect on the wettability of the coal surface. The middle position of the benzene ring structure of coal is the best adsorption site for the hydrophobic tail of the surfactant. By calculating the adsorption energy of different simulation systems, it is confirmed that the phenomenon of “reverse adsorption” between nonionic surfactants and low metamorphic coal is caused by hydrogen bonding. The results of the study provide a theoretical basis for the effective application of different surfactants in coal dust control.