Molecular dynamics simulation and experimental research on the influence of SiO2-H2O nanofluids on wettability of low-rank coal

Coal dust pollution is one of the problems needing urgent solution in global coal mining industry. Exploring environmental and efficient new wetting agents of coal dust has potential application value in the field. Taking the Wender model as the research object, Materials Studio molecular simulation software was used and physical experiments were conducted to study the influence mechanism of SiO2-H2O nanofluids on the wettability of low-rank coal (LRC). Results show that SiO2 nanoparticles (NPs) have a relatively high surface electrostatic potential, enabling strong binding capacity with LRC and water molecules. After SiO2 NPs are adsorbed on the LRC surface, more water molecules are adsorbed on the surface, which enlarges the interaction energy between solid-liquid molecules in the system. As the number of SiO2 NPs increases, the thickness of SiO2 NPs, thickness of coal-water interface, and mean square displacement (MSD) of water molecules all enlarge and the wettability of coal dust is enhanced. Compared with water, SiO2-H2O nanofluids have a lower surface tension and a smaller contact angle. The scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) results further verify that the adsorption and aggregation of SiO2 NPs on the surface of coal dust are the essential cause for the enhanced wettability of coal dust. The molecular dynamics simulation results and experimental results are mutually verifiable, laying a theoretical basis for enhancing the wettability of coal dust using SiO2-H2O nanofluids.