Effect of oxidation on the wetting of coal surfaces by water: experimental and molecular dynamics simulation studies
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Institute of Resources and Environmental Engineering, Shanxi University
Institute of Resources and Environment Engineering, State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources, Shanxi University
University of Utah
Metallurgical Engineering, University of Utah
Corresponding author
Jan D. Miller   

Metallurgical Engineering, University of Utah, 135 S 1460 E, Rm 412 WBB, 84112-0114 Salt Lake City, United States
Physicochem. Probl. Miner. Process. 2018;54(4):1039-1051
The wettability of coal surfaces by water continues to be one of the key factors which determines the success of coal flotation. Consequently, oxidation of coal surfaces is a fundamental issue of interest. In this work, the effect of oxidation on the wetting of coal surfaces and the interaction between water molecules and oxygen-containing sites at the coal surface was investigated based on advancing/receding contact angle measurements and molecular dynamics simulations. For the simulation studies, a flat coal surface was constructed with the assistance of the molecular repulsion between graphite surfaces and the assembly of Wiser coal molecules. Our results indicated that the simulated advancing and receding contact angles were very similar, and both of them decreased, as expected, with an increase of hydroxyl sites at the coal surface. The good agreement between the simulated advancing/receding contact angles and the experimental receding contact angle values suggested that the configuration of the systems and the set of parameters for the simulation were appropriate. The spreading of water is mainly due to the hydrogen bonds formed between the interfacial water molecules and the hydroxyl sites at the coal surface. The hydroxyl groups show stronger hydration capacity than other oxygen-containing groups according to the calculated hydrogen bonds and interaction energies.
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