An experimental study on the effect of ionic liquids on the structure and wetting characteristics of coal. (15th May 2019)

• Record Type: Journal Article
• Authors: Xi, Xian; Jiang, Shuguang; Zhang, Weiqing; Wang, Kai; Shao, Hao; Wu, Zhengyan
• Is Part Of: Fuel. Volume 244(2019)
• Page Start: 176
• Page End: 183
• Publication Date: 2019-05-15
• Subjects: Coal -- Wettability -- Ionic liquid -- Surface morphology -- Functional group; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2019.01.183
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: The effect of ionic liquids on physical and chemical structure of coal were studied. XPS and FTIR analyses showed the changes of microstructure of the coal treated with ionic liquids. The wettability of the raw coal and treated coal with ionic liquids were investigated comparatively. Ionic liquid enhanced the wettability of coal. Abstract: To investigate the effect of ionic liquids on coal structure and wettability, three kinds of ionic liquids with good surface activity were selected to treat coal sample. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to study the surface morphology, pore structure, and chemical structure of coals. Moreover, the effect of ionic liquids on the wetting characteristics of coal was studied by contact angle measurement. Compared with the raw coal, the surface morphology of coal treated with ionic liquids became rougher due to the formation of more pores and cracks. FTIR analysis showed that the skeleton of the coal was changed significantly by ionic liquids, and the content of oxygen-containing functional groups increased in the treated coal samples. XPS test revealed that the content of hydrophilic functional groups on the coal surface was increased and the hydrophobic functional group content was decreased obviously, which agreed with the results of FTIR analysis. From the results of contact angle measurement, it could be found that the treated coal samples with ionic liquids demonstrated smaller contact angle compared to the raw coal, which indicated the enhanced wettability of coal, mainly due to the changes in physicochemical structures including surface morphology and functional groups under the impact of ionic liquids. Typically, ionic liquid named [HOEtMIm][NTf2 ] showed the best wetting effect on coal as evidenced by smallest contact angle for the treated coal with [HOEtMIm][NTf2 ].