Effects of the Hydrophilic Group Distribution on Coal Dust Suppression by Binary Anionic Surfactant Blends: Mechanistic Insights

Surfactants are essential in coal dust control, with the distribution of hydrophilic groups playing a pivotal role in determining dust suppression efficiency. This study investigates the effect of hydrophilic group arrangement on the performance of binary blends of anionic surfactants. Three surfactants (sodium dodecyl sulfate (SDS), sodium dodecyl benzenesulfonate (SDBS), and sodium alkyl ether sulfate (AES)) were selected for experimental and molecular simulation analyses. The dust suppression performance of SDS+SDBS and SDS+AES blends was assessed. The results showed that foam stability and coal dust wettability decreased in the following order: SDS+AES > SDS > SDS+SDBS. Molecular simulations indicated that the hydrophilic groups in SDS+AES blends exhibited enhanced synergy, resulting in a thicker liquid film and higher interfacial energy between foam and coal, leading to greater stability. In contrast, the hydrophilic groups in SDS+SDBS displayed antagonistic interactions, reducing hydration and foam stability. Structural analysis shows that the hydrophilic groups in SDS and SDBS are concentrated at one end of the molecular chain, giving rise to a localized region of negative electrostatic potential. Moreover, in SDBS, the hydrophilic moiety is linked through a phenyl group, and the steric hindrance imposed by the aromatic ring prevents close molecular packing, thereby weakening hydration and compromising foam stability. By contrast, AES features broadly and more uniformly distributed hydrophilic sites, which, upon blending with SDS, strengthen intermolecular interactions and enhance both hydration and foam stability. Together, these findings highlight the central role of hydrophilic group distribution in governing the performance of surfactant mixtures and provide useful guidance for the design of more effective dust suppressants.