Quantum-chemistry-based mechanisms for the regulation of coal-nanofluid wetting in different coal ranks

Among the leading technologies for mine dust source control is coal seam water infusion. To address the negative impacts resulting from the hydrophobic nature of coal, researchers have put forward a novel concept of enhanced wetting through nano-silica suspensions. This research analyzed the influence pattern of nano-silicon dioxide on coal's adsorption of water through molecular dynamics simulation. The macroscopic contact angle experiments were then employed to verify the simulation findings, which finally revealed the wetting mechanism and the action law of nano-silica on coals of different coal rank. The findings indicate that the intermolecular interactions within the simulated system are governed by the electrostatic potential on the surface of each molecule. The silicon nanoparticles possess a broad range of electrostatic potential distribution. This affects the formation of intermolecular hydrogen bonds and thereby regulates the wettability. The wettability decreases as the degree of coal degradation increases. In the concentration range of 0 to 2.0 wt. % for nano-silica, the contact angle decreases as the concentration increases. After treating lignite (HM), bituminous coal (YM), and anthracite (WYM), the contact angles show reductions of 81.59%, 73.02%, and 60.85%, respectively, compared to the control group. The research findings can offer theoretical direction for choosing the concentration of nano-silica fluid in the process of coal seam water infusion.