Molecular simulations and experiments on the effect of different types of surfactants on the wetting properties of bituminous coal

Currently spray dust reduction is one of the most widely used dust removal methods in coal mines. The wetting performance of water on coal has a direct impact on spray dust reduction, therefore, adding wetting agents such as surfactants in water can improve the wetting performance of water on coal. In order to investigate the effect of various surfactants on the wettability of bituminous coal dust, four types of surfactants, namely, Rapid Penetrant T, 1227, BS-12 and APG, were used to investigate the wettability of bituminous coal by combining molecular simulation techniques and laboratory experiments. On the one hand, the interfacial system of surfactant aqueous solution was constructed by means of molecular simulation, the hydrophilicity of surfactant itself was analyzed based on the theory of the number of hydrogen bond formation and the radial distribution function, and the surface tension experiments of 4 reagents were carried out, and it was found that the Rapid Penetrant T reagent forms the most number of hydrogen bonds being 398, and the radial distribution function curve peaks at 1.99 ×10⁻¹⁰ m at the earliest time, which is the easiest to be adsorbed with H₂O molecules, and the experimental results also showed that the Rapid Penetrant T reagent has the strongest weakening of the surface tension of the water, i.e., the smallest surface tension, which is 24.4 mN/m. On the other hand, through the electrostatic potential calculation, combined with the constructed surfactant/water/bituminous coal ternary adsorption system interaction energy analysis, the effect of four surfactants on the wettability of bituminous coal was investigated, and the experiments on the settlement and contact angle of bituminous coal in 4 reagents were carried out respectively. The results showed that the potential difference between the site and the water molecules after the Rapid Penetrant T molecules combined with the bituminous coal molecules is the largest, being 6.8535 eV, and the interaction energy between it and the bituminous coal is also the largest, being −2705.12 kJ/mol, and the experimental results also showed that the two kinds of bituminous coal have the smallest settling time in the Rapid Penetrant T reagent being 26.3 and 10.22 s respectively, and the smallest contact angle are 25.8° and 21.7° respectively. Thus, the study shown that the molecular simulation results are in agreement with the experimental results, and all of them validate that the anionic surfactant Rapid Penetrant T has the best wettability performance on bituminous coal.