Suppression of anthracite dust by a composite of oppositely-charged ionic surfactants with ultra-high surface activity: Theoretical calculation and experiments

Abstract

In this study, we developed composite anionic–cationic (AC) surfactants with ultra-high surface activity using sodium alpha olefin sulfonate and octadecyltrimethylammonium chloride to improve the wettability and dust suppression efficiency of coal dust. Moreover, we investigated the synergistic suppression mechanisms of AC surfactant compounds at a molecular level. The thermodynamics of the self-assembly suggested that the surfactant molecules in the composite solution form a flexible alternating anion–cation bilayer. The analysis of the critical micelle concentration (CMC), surface tension (24.121 mN·m−1), contact angle (35.14°) and settling time (18 s) of the composite surfactant solution proved the superior performance of our composite surfactants compared to the monomeric alternatives, resulting in enhanced wettability owing to an ultra-high surface activity. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) experiments revealed an increased number of hydrophilic groups on the surface of the composite surfactant-treated anthracite, explaining the microscopic mechanism behind the high wettability induced by the composite surfactant. The specific surface area and pore size distribution of anthracite before and after dust suppressant treatment were calculated, and it was concluded that the dust suppressant was adsorbed on the surface and in the pores of the anthracite. In addition, the microscopic external morphology of the anthracite was shown by scanning electron microscopy (SEM), and it was found that the dust suppressant showed filling and aggregation behavior. Wind erosion and evaporation resistance experimental results show that dust suppressant-treated coal dust has enhanced water retention and wind resistance. Our findings indicate that ionic surfactants with oppositely charged compounds are promising high-efficiency dust suppressants, laying the foundation for safe coal mining and providing a theoretical background for a broad range of applications, such as haze control.