Wettability and bubble attachment of porous coal surface: insights from molecular dynamics simulation

Coal surface pores significantly influence its wettability and floatability. However, the atomic and molecular mechanisms by which the pore structure affects these properties remain unclear. In this study, molecular dynamics simulation (MDS) was used to investigate the wetting behavior and bubble attachment dynamics on porous coal surfaces. The results show that increasing porosity enhances the adsorption of water molecules both on the surface and inside the pores, reducing the contact angle of the coal surface from 53° to 39°, while hydrogen bonding between water and coal molecules increased threefold. This enhancement in adsorption is mainly driven by hydrogen bonding interactions at the coal-water interface. Additionally, the pore structure of the coal surface reduces the bubble attachment rate. The rupture time of the hydration layer between the bubbles and the coal surface increased from 70 ps to 280 ps. Moreover, the hydration layer on high-porosity coal surfaces showed significantly more hydrogen bonds than on low-porosity surfaces, resulting in greater structural stability and, consequently, lower bubble attachment rates. This study uses MDS to investigate hydrogen bonding during wetting and adhesion on porous coal surfaces, demonstrating that hydrogen bonding is crucial in determining coal wettability and floatability.