The effect of functional ionic liquids on the microstructure and wettability of coals with different metamorphic degrees

Abstract

As the degree of coal mine mechanization increases, the dust concentration underground increases significantly, and the effective reduction of dust concentration can guarantee the safe production in the mine. Wet dust removal method is the main means to suppress coal dust, and wettability is its theoretical basis. To study the effect of functional ionic liquids on the microstructure of coal and the effect of coal microstructure on wettability, [AMIm][BF4], [HOEtMIm][BF4], and [HOEtMIm][NTf2] were selected to treat lignite and anthracite with different metamorphic degrees. Firstly, the effects of ionic liquids on the wettability of coal surface were investigated by surface tension and contact angle experiments. Secondly, the carbon structure skeleton of coal was analyzed by nuclear magnetic resonance (NMR) experiments. Finally, the correlation between the structural parameters obtained by NMR and the contact angle was analyzed by origin software. The results show that [HOEtMIm][NTf2] has the most obvious wetting effect on coal, and different ions have different effects. The ionic liquid treatment will partially dissolve the functional groups in coal. As faH(protonated aromatic carbon) decreases, faC(carbonyl carbon) and falO(oxygen-bonded aliphatic carbon) increase, the hydrophilicity of coal increases, and as fa′(aromatic ring carbon) and fal∗(methyl carbon) decrease, falH(methylene carbon and quaternary carbon) increases, the hydrophobicity of coal decreases. The results of this paper can provide basic theoretical support for improving the hydrophilicity of coal surface to improve the efficiency of mine dust reduction.