Molecular simulation study on hydration of low-rank coal particles and formation of hydration film
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China University of Mining and Technology
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Xiahui Gui   

China University of Mining and Technology, No.1, Daxue Road, Nanhu Campus, China University of Mining and Technology, Xuzhou, Jiangsu Province, 221116 Xuzhou, China
Physicochem. Probl. Miner. Process. 2019;55(2):586-596
Water molecules in low-rank coal (LRC) significantly influence its upgrading and utilization. To investigate the hydration of LRC particles and the formation of a hydration film, molecular simulation techniques were innovatively used, including molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The adsorption of water molecules on LRC and various oxygen-containing groups was analyzed. The results show that water molecules adsorb close to the LRC surface and form a large overlapping layer at the LRC/water interface. The radial distribution functions (RDFs) show that the adsorption affinity of water molecules on oxygen-containing sites is stronger than that on carbon-containing sites, and the RDF peaks indicate the existence of a hydration film. Moreover, the differences in adsorption between various oxygen-containing groups depend on both the number of hydrogen bonds and the adsorption distances. The calculated binding energies indicate that the adsorption capacity follows the order carboxyl > phenolic hydroxyl > alcoholic hydroxyl > ether linkage > carbonyl. Experimental results show that a high sorption rate exists between water vapor and LRC samples at the beginning of sorption, which verified the simulation results.
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