Study on the mechanism of SiO2-H2O nanofluid enhanced water injection in coal seam

The technique of injecting water into coal seams is commonly used to prevent and handle mining disasters. In order to improve the effectiveness of water injection in coal seams, the impact of SiO2-H2O nanofluids on coal wettability was investigated through macroscopic physical experiments and Materials Studio software. The findings demonstrate a significant rise in the height of coal sample infiltration when using nanofluid rather than deionized water. It was found that as the particle concentration increased, the initial and dynamic contact angles of nanofluid-treated coal samples significantly decreased and the absorbed mass of coal samples in the nanofluid consistently exceeded that in deionized water. The coal sample surfaces treated with nanofluid showed a significant occurrence of nanoparticles adsorbing and aggregating. The substantial surface electrostatic potential of nanoparticles, characterized by a broad distribution of positive and negative values, facilitated hydrogen bonding with Wiser molecules and H2O molecules. The presence of nanoparticles on the surface of coal enhanced the adsorption of H2O molecules, resulting in an increase in the thickness of the interface between coal and water. There was a direct relationship observed between the number of nanoparticles and the mean square displacement of H2O molecules, diffusion coefficient, and the total hydrogen bonding. Consequently, nanofluids proved more advantageous than pure water in improving coal seam wettability. Through the present study, the adsorption traits of nanoparticles on the surface of coal were discovered, and the mechanism through which nanoparticles improve the wetting properties of coal seams was examined at a micro level. These findings provide a theoretical foundation for applying SiO2-H2O nanofluid to enhance coal seam wettability.