Microscopic mechanism of coal dust suppression by an anionic surfactant-induced surface hydration layer

To elucidate the microscopic mechanism of SDBS-enhanced coal-dust wetting and the associated interfacial hydration, macroscopic experiments, microscopic characterization, and molecular simulations were conducted. At the macroscopic scale, 0.10% SDBS reduced the surface tension to 27.8 mN/m and decreased the contact angle from 42.5° at 0 s to 29.1° at 5 s; wetting also promoted the attachment and agglomeration of fine coal particles. On this basis, molecular simulations showed that the hydrophobic moieties of SDBS anchored to the coal surface, whereas the sulfonate groups oriented toward the aqueous phase and induced water enrichment. Sulfonate O-water H pairs exhibited a preferred coordination distance of 0.17 nm, with a coordination number of 1.88 within the first coordination shell. The sulfonate-water network contained an average of 107 hydrogen bonds, with an average lifetime of 2.22 ps. Furthermore, electrostatic potential analysis demonstrated that the electrostatic attraction between the negative-potential regions of sulfonate oxygen atoms and the positive-potential regions of water hydrogen atoms provides the intrinsic driving force for interfacial hydration. Overall, SDBS constructs a dynamic hydration layer through the concerted effects of hydrophobic anchoring, electrostatic enrichment, and dynamic hydrogen-bond reorganization, providing a molecular-scale basis for enhanced coal-dust wettability and sustained interfacial hydration required for dust suppression.