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This study investigates the impact of water-based silica nanofluids on coal wettability through molecular simulations, physical experiments, and theoretical analysis. It explores how nanoparticles affect coal's wettability and the mechanisms behind nanoparticle aggregation and sedimentation. The distribution of surface electrostatic potential for coal, nanoparticles, and water molecules was analyzed, revealing the mechanisms by which nanoparticles improve coal wettability. A molecular simulation system was constructed to study the adsorption dynamics, showing how nanoparticles influence coal wettability at the molecular level. The study also analyzed the stability of the nanofluid, revealing nanoparticle aggregation and sedimentation behaviors. Results show that nanoparticles enhance coal wettability, with type II nanoparticles exhibiting stronger adsorption on coal and water molecules. The interaction energies between nanoparticles and coal, as well as between nanoparticles and water, are significant. Nanoparticle aggregation and sedimentation occur in three stages: early aggregation, mid-stage sedimentation-aggregation, and late-stage sedimentation. The study indicates that van der Waals forces and hydrogen bonding drive these processes. This research supports the use of nanofluids in enhancing water injection technology for safe and efficient coal extraction.
Zhao et al. (Sat,) studied this question.