Regulation mechanism of the surfactant hydrophilic headgroup on the wettability of bituminous coal: Experiments and molecular dynamics simulations

The present work selected surfactants that exhibited excellent dust reduction and in so doing improved coal mine dust control. Through macroscopic–microscopic experiments, the effects of four surfactants with consistent tail chains but different hydrophilic headgroups—dodecyl polyglucoside (APG1214), sodium fatty alcohol polyoxyethylene ether sulfate (AES), oxidized dimethyl dodecyl amine (OA-12), and sodium dodecyldiphenyl ether disulfonate (SLDED)—on the surface wetting properties of bituminous coals were determined. By molecular dynamics and quantum chemistry simulations, the interactions between the four surfactants and coal dust as well as the wetting mechanism were revealed. The wettability of the four hydrophilic headgroups was in the following order: sulfuric acid > hydroxyl > oxidized amine > sulfonic acid . The radial distribution results showed that AES formed the first peak of the closest hydration layer at 1.53 Å, and the probability peak was 4.05, which showed a strong hydrogen bond interaction. The presence of C O, OH···OH, OH···π and free hydroxyl group substantially increased the wettability of solutions on bituminous coal. These groups form more hydrogen bonds and thicken the adsorption layer of the water molecules along the z axis, making the molecules fixed, with the most effective surfactant overlapping range being 46.78Å. The molecular orbital energy differences of AES, APG1214, OA-12 and SLDED were 6.9180, 6.2805, 5.4693 and 4.8477 eV, respectively. Larger energy difference is conducive to wetting. In this paper, the wetting properties of surfactants on coal dust are evaluated, and theoretical suggestions for the application of surfactants in coal mine spray dust removal are put forward. • C = O, OH···OH, OH··· π and free hydroxyl groups can affect the wettability regulation of bituminous coal. • The effects of four surfactants with different hydrophilic head groups on the wettability of bituminous coal were obtained. • The analysis of the nature of surfactants for coal dust wetting can provide theoretical guidance for the application of surfactants in the field of coal mine spray dust removal.