Research on quantifying the hydrophilicity of leached coals by FTIR spectroscopy
Yaqun He 1,2
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School of Chemical Engineering and Technology, China University of Mining & Technology
Advanced Analysis and Computation Center, China University of Mining and Technology
Publication date: 2016-08-01
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Yaqun He   

China University of Mining and Technology, Jiangsu Province Xuzhou City Daxue Road NO.1, 221116 Xuzhou, China
Physicochem. Probl. Miner. Process. 2017;53(1):227-239
Surface properties play important roles in characterization of structural parameters and the hydrophilicity index. Accurate analysis of the macerals rather than the average properties of the macerals and minerals are crucial for these parameters and indexes. In order to improve the accuracy of analyzing coal surface property, HF/HCl acid leaching was applied to eliminate the interference of minerals. FTIR was used to characterize the differences in surface chemical composition between raw and processed coal. Moreover, each functional group was analyzed quantitatively. Based on these quantitative data, the structural parameters and hydrophilicity indexes were calculated. From the results of FTIR, the peaks of mineral cover up the types of the organic peaks, such as -COOH and aromatic CH stretching. In addition, they decrease the intensity of the peak such as C=C and aromatics CHx out-of-plane deformation in the spectra of raw coals. However, it provided the accurate types and contents of organic functional groups of the macerals after acid leaching. The structural parameter results indicate that the values cannot reflect the coal ranks through the surface properties of raw coals while they show a good relationship with the degree of coalification in the analysis of processed coals. Besides, the hydrophilicity indexes are verified by the natural floatability of coal macerals of the processed coals. It is also found that the processed lignite coal cannot be floated despite elimination of the hydrophilic minerals. The main reason of hard-to-float property of lignite coal lies in a strong hydrophilicity of macerals.
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