Experimental study on the effect of ionic liquid on surface wettability of coal dust

In order to solve the problems of difficult wetting of hydrophobic coal dust and low dust reduction rate of micron dust, three kinds of imidazole ionic liquid such as 1-Butyl-3-methylimidazolium chloride salt(BmimCl), 1-Butyl-3-methylimidazolium tetrafluoroborate (BmimBF₄) and 1-Ethyl-3-methylimidazolium tetrafluoroborate(EmimBF₄) were selected to study the surface wetting characteristics of coal dust with different degrees of metamorphism and to analyze the influence of compound reactive aqueous solution with different cation and anion numbers on wettability of coal dust. The results show that cation Emim⁺ and anion Bmim⁺ can effectively shield the electrostatic interaction between anion BF₄^- and Cl^- and promote the adsorption and aggregation of anions at the gas-liquid interface, resulting in the surface tension and contact angle gradually decrease with the increase of the mass fraction of ILs of the active aqueous solution. H atom on the side chain of imidazole cation forms a hydrogen bond with -OH, -COOH, and other groups in coal, which destroys the original hydrogen bond in coal and improves the solubility of ILs to coal. Long flame coal has the strongest wettability, followed by lignite coal, and coking coal has the worst. Compound active aqueous solution can not only enhance the solubility of coal structure by destroying functional groups in coal, but also improve the wettability of solution by reducing the surface tension of water, which enhances the synergistic wetting ability and provides a new idea and direction for the development of new wetting agents.