Modification of Low-Rank Coal Wettability With Imidazole Ionic Liquid: Mechanism and Performance Evaluation

At present, low-rank coal occupies a large proportion of coal resources and has poor wettability, making it difficult to use effectively. In order to separate cleaned coal from slime and achieve high-quality improvement and utilization, imidazole ionic liquid was used as a modifier to pretreat the surface of low-rank coal. After the modification with ionic liquid, the hydrogen bonds between oxygen-containing functional groups and water molecules are broken, and the coal’s bonding ability with water molecules is weakened. In addition, the number of hydrophilic functional groups is reduced, and the proportion of hydrophobic alkyl functional groups increases. Compared with Br and Cl, HSO₄ has a stronger modification effect on hydroxyl groups, resulting in increased hydrophobicity and a higher contact angle. The modified contact angle of [Bmim]HSO₄ is the highest, which is 77.63% higher than that of raw coal. In water absorption experiments, the total moisture content of the modified coal decreased, indicating that the modified ionic liquid worsens coal’s water storage capacity, with [Bmim]HSO₄ showing a 2.45% decrease compared with raw coal. The influence mechanism of different anionic imidazolyl ionic liquids on coal wettability was revealed by studying microstructure changes and water absorption. It provides a fresh concept and direction for flotation agents development and has certain guiding significance for modifiers synthesis with green and high efficiency advantages.