Application of Pyridyl Ionic Liquids in the Reverse Flotation of Shengli Lignite

Lignite is extremely hydrophilic; thus it is difficult to upgrade its quality by conventional flotation. In this study, cetylpyridinium chloride monohydrate (CCM) was used as the collector for quartz. The effect of CCM dosage on reverse flotation of Shengli lignite was investigated by different slurry mixing methods. And the dissolution properties of CCM and its mechanism of collecting quartz were studied via surface tensitometer and FTIR. The flotation results show that, due to the strong hydrophilicity of Shengli lignite, the performance of direct flotation is poor. With reverse flotation, the yield of clean coal and the flotation perfection are obviously improved. Besides, the reverse flotation with the zero-conditioning is more efficient than the conventional one. FTIR results show that the adsorption of CCM barely change the functional groups of quartz, indicating that CCM was adsorbed on the surface of quartz through electrostatic adsorption to collect quartz. Meanwhile, CCM adsorption significantly reduces the content of hydroxyl oxygen-containing functional groups of quartz, leading to an increase of the content of hydrophobic groups such as long-chain alkyl. As a result, the hydrophobicity of quartz was improved, and the reverse flotation of lignite was promoted.