Exploring the wetting mechanism of surfactants for coals based on molecular simulations

With a gradual increase in the depth and mechanization degree of coal mining, secondary explosions of gas and coal dust have become increasingly severe. Chemical dust suppressants such as surfactants can reduce these explosions by effectively inhibiting the generation and diffusion of coal dust. To explore the inhibition mechanism of nonionic surfactants for hydrophobic coal dust, this study analyzed the basic physicochemical properties of typical hydrophobic coal dust at a depth of 1050 m using FT-IR, XRF, and XRD. This study built a molecular structure model of coal dust by combining test techniques such as EA, XPS, and ¹³C NMR. It also investigated the equilibrium adsorption configuration and molecular spatial distribution of the water-surfactant-coal wetting adsorption systems by establishing a molecular model. Then, this study designed an experiment to examine the compositions of the surface free energy of coal dust before and after surfactant adsorption, followed by verifying and discussing the wetting adsorption mechanism of surfactants on coal dust interfaces. The results show that surfactants can form an effective directional adsorption layer, which is tight and has a high coverage degree, on the surface of hydrophobic coal dust. The hydrophobic structure of the coal dust surface is covered by the hydrophobic tail chains of surfactants, with the hydrophilic head groups facing the aqueous phase, increasing the polar components of surface free energy of the coal dust. As a result, the hydrophobic coal dust surfaces become hydrophilic. The results of this study can provide theoretical guidance and a reference for efficient dust suppression in coal mining.