A multiscale study on the molecular mechanisms of surfactants that enhance the wettability of coal dust and the efficiency of droplet coagulation

Surfactants are widely applied in mine dust control; however, the intrinsic mechanism by which microscopic physicochemical properties determine macroscopic wetting performance remains not fully elucidated, limiting the rational design of high-efficiency reagents. To address this, this study employs a multi-scale approach integrating macroscale experiments, mesoscale dust-droplet collision modeling, and molecular dynamics simulations to systematically reveal the wetting performance differences and multiscale mechanisms of four typical surfactants: SDS, AES, APG, and DTAB. Macroscale experiments, including surface tension measurements and spray-based dust suppression tests, established the wetting performance order as SDS > AES > APG > DTAB. Mesoscale collision simulations elucidated how droplet physicochemical properties, velocity, and size govern the encapsulation and wetting efficiency of coal dust. Molecular simulations quantitatively revealed the intrinsic correlation between wettability and the interfacial hydration layer structure and hydrogen bond network. Critically, we identified that the intensity and spatial distribution of the electrostatic potential extrema within the hydrophilic head group region are the key determinants of the capacity and quantity of water molecule adsorption. These findings not only clarify the cross-scale mechanisms of coal dust wetting but also provide a crucial theoretical basis for shifting from traditional empirical trial-and-error to the rational screening and design of surfactants based on electronic properties.