Optimizing Coal Wettability via Anionic Surfactants: An Integrated Experimental and Molecular Dynamics Simulation Investigation

Abstract

The optimization of coal dust management in fluidized mining environments is of paramount importance, yet it is currently impeded by a gap in understanding chemical dust suppression mechanisms. This study combines indoor experiments with molecular simulation to investigate the mechanisms by which three anionic surfactants with different hydrophilic and hydrophobic groups (SDBS, SDS, and SLS) influence coal wettability. Using hydrophobic bituminous coal as the experimental subject, basic physical and chemical properties are analyzed through proximate analysis, XRD, and FTIR. The effect of different surfactants on coal wettability is characterized based on sedimentation experiments, while the coal–surfactant–water three-phase model examines the equilibrium adsorption configuration, water molecule diffusion coefficient, and interaction energy in different adsorption systems. The surface free energy of coal dust and its components is measured before and after surfactant adsorption, verifying the adsorption-wetting mechanism of surfactants at the coal–water interface. Results show that anionic surfactants enhance wettability through a bidirectional adsorption mechanism at the coal–water interface: the hydrophobic tail adheres to the coal surface via van der Waals forces, while the hydrophilic head faces the water phase, driven by electrostatic and hydrogen bonding interactions. This coordinated adsorption process alters water diffusion and the surface free energy of coal, thereby improving wettability. SDBS, due to its benzene ring, significantly amplifies the bidirectional adsorption effect, achieving the most substantial improvement in coal dust wettability. The findings provide a robust theoretical framework for developing dust control strategies in fluidized mining operations, advancing the field toward more efficient and sustainable mining practices.