Effect of imidazolium-based ionic liquids on the pore wetting characteristics and mechanical properties of coal

Abstract

Exploring the pore wetting pattern of the imidazolium-based ionic liquids-water system is necessary to understand the dust reduction effect from the source of the coal seam and its influence on the mechanical properties. Low-field nuclear magnetic resonance (LF-NMR) is used to analyze the wetting effect of different concentrations and types of ionic liquids-water systems on different pore sizes from the pore size distribution. Uniaxial compression mechanics experiments are used to investigate the changes in mechanical properties of the coal after wetting, and a scanning electron microscope is used to observe the differences in surface morphology of the coal after treatment with aqueous solutions of ionic liquids. The results show that the wetting effect of aqueous solutions of different concentrations of imidazolium-based ionic liquids is different for micropores, mesopores and macropores compared to pure aqueous solutions. At the same time, the pore wetting of the coal samples by the aqueous solution of the imidazolium-based ionic liquids altered their mechanical properties, with a minimum strength of 8.57 MPa for the 2 wt% [Bmim][BF4] treated coal samples. Analysis of microscopic morphology shows that the surface minerals of coal samples treated with imidazolium-based ionic liquids are dissolved, forming linked fissures or pores between minerals, which positively affect pore wetting. The revelation of the pore wetting properties of ionic liquids systems on coal is conducive to enriching the theory of coal seam dust control and is of practical significance for efficient dust reduction in mines.