Mechanism of anthracite dust suppression by surfactants with different alkyl chain lengths: Thermodynamic micelle morphology, adsorption probability, and interfacial forces

Abstract

Coal dust explosions and pollution cause serious problems in the front line of mines; these issues can be effectively resolved by wetting the coal dust. In this study, the effect of the alkyl chain length of surfactants on their adsorption on anthracite surfaces and the microscopic mechanism underlying this impact was evaluated. The differences in the critical micelle concentration and micelle morphology of surfactants with varying alkyl chains in solution systems were evaluated through surface tension measurement and thermodynamic theory. In addition, the differences in the functional groups, surface energy, adhesion, roughness, pore size, and elemental distribution of coal samples modified using surfactants with various numbers of methylene groups in their alkyl chains were characterized by testing raw and adsorbed coal samples. Based on this, the mechanism underlying the effect of the alkyl chains on adsorption was elucidated from a mesoscopic perspective and the enhancement of the amount and strength of the adsorption of the surfactant on anthracite surfaces upon the shortening of the alkyl chain was explained. The high and low distributions of energies on various surfactants and coal molecules were calculated using the density functional theory, and the possible adsorption configurations were predicted. The simulation results showed that the adsorption energy of the short-chain surfactants on the anthracite surface was higher, the hydrogen bonds formed were shorter, and the charge transfer was faster, with a tendency prevailing for a stepwise increase in the alkyl chain length. Finally, the interaction mechanism between the surfactant and anthracite particles in the aqueous phase was calculated and analyzed using the classical DLVO theory. The results showed that the surfactants with shorter alkyl chains were easily dispersed with coal dust particles in water, which was favorable for collision adsorption. In addition, research directions toward the inhibition of coal dust by surfactants were discussed on the basis of the results of this study.