Experimental and molecular simulation study on wettability regulation of anthracite by non-ionic surfactants

Coal seam water injection is a coal mine safety technology used to inhibit coal dust and reduce the potential risk of gas explosions, but its effectiveness is limited by the wettability of the coal seam. Anthracite coal, due to its strong hydrophobicity, is difficult to fully combine with injected water. To improve the wettability of anthracite coal, this study systematically investigates the regulatory effects and wettability mechanisms of the non-ionic surfactant dodecyl β- d -maltoside (DDM) on anthracite coal, combining physical experiments and molecular simulations from both macroscopic and microscopic perspectives. The contact angle experiments indicated that DDM significantly reduced the contact angle of anthracite and enhanced its wettability. XPS and FTIR spectral analysis showed that DDM improved the chemical composition of the coal surface by decreasing the content of hydrophobic functional groups and increasing the content of hydrophilic functional groups on the coal surface. Molecular dynamics simulations further revealed the adsorption characteristics and microscopic wettability mechanism of DDM on the surface of anthracite coal. The results showed that the hydrophobic tail chain of DDM adsorbed onto the coal surface, while the hydrophilic head group oriented toward the water phase, significantly enhanced the interactions between water molecules and the coal surface, increased the number of hydrogen bonds and the contribution of electrostatic energy, thereby greatly improved the hydrophilicity of anthracite coal. This study provides theoretical support and technical references for improving the wettability of anthracite coal in coal seam water injection.