Adsorption mechanism of alkylphenol ethoxylates surfactants (APEO) on anthracite surface: A combined experimental, DFT and molecular dynamics study

Abstract

The serious hazards posed by inhalable coal dust to the safety, air purity, and health of coal miners can be effectively alleviated through the use of appropriate dust suppressants. The wetting enhancement capabilities of two dust suppressants, octylphenol polyoxyethylene ether (OP-10) and nonylphenol polyoxyethylene ether (NP-10), were examined in this study through experimental and simulation methods. Macroscopic experiments (surface tension, contact angle, coal dust settling time, and water retention) indicate that the shorter the alkyl chain attached to the benzene ring in the surfactant and the lower the surface tension, the more conducive it is to improving the fluidity and suspension stability of anthracite particles in the wetting solution and further improving the interfacial properties and wetting effect between coal dust and the liquid medium. Mesoscopic experiments (laser particle size, FTIR, XPS, UV–visible spectroscopy, BET, and SEM) showed that the relevant properties of APEO-modified coals were greatly changed, especially the anthracite modified with short-chain alkyl groups of OP-10, which exhibited a stronger aggregation effect on the coal dust particles and increased the pore structure and specific surface area of the coal dust. Additionally, the hydrophilic functional groups are augmented, leading to a notable enhancement in the adsorption capacity of OP-10 on the coal surface. Microscopic simulations (Density Functional Theory calculations, Molecular Dynamics simulations) reveal that APEO surfactants with longer alkyl side chains attached to benzene rings hinder the π-π interactions between the coal's aromatic ring structures and the benzene rings in the surfactants. The surface polarity of coal modified with OP-10 is significantly enhanced, resulting in a more pronounced improvement in wetting performance and an increased water retention capability. The study systematically explores surfactant microstructure effects on anthracite wetting, laying essential groundwork for advanced dust suppression system development.