Exploration of Experimental Research and Molecular Dynamics Simulation on the Adsorption and Desorption Characteristics of Gas-Bearing Coal with Water-Based Mucilage Suppression

In response to the severe issue of excessive gas emissions and the increased risk of gas accidents during mining face operations, our team has developed a novel, efficient gas-blocking suppressant for coal minesaqueous mucilage. This study combines ¹³C NMR, Fourier-transform infrared (FTIR), low-temperature nitrogen adsorption microphysical experiments with molecular dynamics simulations to explore the inhibitory mechanisms on the adsorption and desorption properties of coal. The results indicate that, after treatment with aqueous mucilage, the coal sample's ability to adsorb and desorb methane molecules is significantly reduced. Water-based mucilage blocks or covers the pore structure of coal, leading to a significant reduction in the total specific surface area and total pore volume of the coal. This, in turn, affects the channels for methane adsorption and desorption, thereby weakening the coal's ability to adsorb and desorb methane. Post-treatment, the coal surface shows an increase in aliphatic carbon content, a decrease in carboxyl groups, and an increase in carbonyl groups, thereby inhibiting the adsorption and desorption processes of methane molecules. Meanwhile, the effect of aqueous mucilage on the coal's hydroxyl, aromatic ring, and aromatic hydrocarbon structures is minimal. Based on these findings, the molecular structure of the coal macromolecule is identified as C₁₂₃H₆₀N₂O₅. Molecular dynamics simulation results further indicate that the addition of aqueous mucilage significantly enhances the hydrophilicity of coal, increases the diffusion coefficient of water molecules on the coal surface, and further strengthens the "water lock effect," thereby hindering the adsorption and desorption processes of methane molecules. Furthermore, the introduction of the water-based Mucilage increases the interactions and coordination number between methane molecules as well as between the coal structure and methane molecules, which in turn reduces the diffusion coefficient of methane. This results in a further weakening of the coal's desorption capacity for methane molecules. At the same time, the addition of the water-based Mucilage significantly decreases the total energy of the system and the interaction energy between coal and methane, which increases the energy required for methane desorption from the coal. Consequently, the desorption process becomes more difficult, further impairing the coal's ability to desorb methane molecules. This study reveals the microscopic mechanism by which aqueous mucilage inhibits methane adsorption and desorption in coal through both physical and chemical interactions, providing important theoretical insights for gas control in coal mines.