Teng Ying Yue, Han Shi Rui, Song Yue Yin, Bai Xue, Song Yin Min
College of Chemical Engineering, Inner Mongolia University of Technolegy, Huhhot 010051, China.
Inner Mongolia Key Laboratory of High-Value Funtional Utilization of Low Rank Carbon Resources, Inner Mongolia University of Technolegy, Huhhot 010051, China.
ACS Omega. 2023 Mar 6;8(10):9111-9120. doi: 10.1021/acsomega.2c05786. eCollection 2023 Mar 14.
Five coal samples were prepared by deashing Shengli lignite in distinct phases, which consisted of residual ash from spontaneous combustion. The effects of removal and introduction of inherent minerals on the water reabsorption performance of coal samples were systematically investigated in three aspects: pore structure, oxygen-containing functional groups, and lignite materials. Low-field nuclear magnetic resonance spectroscopy was employed to investigate the changes in the water molecular adsorption tendency of coal samples with the variation in the mineral content. The study elucidates that the hygroscopic performance of the coal samples is significantly reduced due to the massive removal of inherent minerals. However, the pore structure of the coal samples after HCl/HF washing becomes more developed, and the oxygen-containing functional groups on the surface are more exposed, leading to an increase in the equilibrium adsorbed moisture content (EMC) of the coal samples. The binding force between coal samples and water molecules is reduced by the removal of the inherent minerals, which weakens the interaction forces between lignite and water molecules. The oxygen-containing functional groups on the surface of lignite interact with the residual ash from spontaneous combustion to enhance the binding force between lignite and surface water molecules, thus leading to the improved tendency of lignite to adsorb water molecules. The formation of intermediate complexes between minerals and oxygen-containing functional groups, in particular, carboxyl functional groups, on the surface of lignite enhances the acting force of polar sites, which improves the interaction of lignite-water molecules.
通过对胜利褐煤进行不同阶段的脱灰处理制备了五个煤样，这些煤样含有自燃产生的残余灰分。从孔隙结构、含氧官能团和褐煤材料三个方面系统研究了固有矿物质的去除和引入对煤样吸水性能的影响。采用低场核磁共振光谱研究了煤样水分子吸附倾向随矿物质含量变化的情况。研究表明，由于大量去除固有矿物质，煤样的吸湿性能显著降低。然而，经HCl/HF洗涤后的煤样孔隙结构更加发达，表面的含氧官能团更加暴露，导致煤样的平衡吸附水分含量（EMC）增加。去除固有矿物质降低了煤样与水分子之间的结合力，削弱了褐煤与水分子之间的相互作用力。褐煤表面的含氧官能团与自燃产生的残余灰分相互作用，增强了褐煤与表面水分子之间的结合力，从而导致褐煤吸附水分子的倾向增强。特别是褐煤表面的矿物质与含氧官能团（尤其是羧基官能团）之间形成中间络合物，增强了极性位点的作用力，改善了褐煤与水分子的相互作用。
