Molecular Dynamics Investigation of Interfacial Interactions and Wettability in Coal–SiO2–Water Three-Phase Systems

Chen, Hanlin

doi:10.2478/pjct-2025-0020

Abstract

Molecular dynamics simulations were conducted to examine how methylated and hydroxylated coal molecules interact with SiO₂ surfaces bearing corresponding functional groups. Coal adsorption and wetting strongly depended on both coal functional groups and substrate chemistry. Methylated coal (coalCH₃) formed dense, planar clusters on hydrophobic SiO₂–CH₃, achieving nearly complete surface coverage (contact angles: 58.5°–67.7° at the surface; 81.9o–94.4° at the tetrahedral bottom), whereas on hydrophilic SiO2–OH it formed sparse spherical or rod-like aggregates (surface: 88.4°–130.6°; bottom: 64.4°–114.4°), indicating poor wettability. Hydroxylated coal (coalOH) exhibited chain-like clusters on SiO₂–CH₃ evolving into continuous adsorption layers, while on SiO₂–OH it formed interconnected strip-like structures with limited spreading (surface: 62.7°–113.2°; bottom: 69.9°–71°). The energy decomposition results indicated that the interaction in coalCH₃ systems is primarily governed by van der Waals forces, whereas electrostatic contributions play a dominant role in stabilizing coalOH structures, highlighting the influence of surface functionalization on adsorption and wetting behaviors.

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Molecular Dynamics Investigation of Interfacial Interactions and Wettability in Coal–SiO2–Water Three-Phase Systems

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