Characterization of Coal Oxidation and Coal Wetting Behavior by Film Flotation

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Abstract
The distribution of wettability of as-received and oxidized coal particles was determined by film flotation with a series of aqueous methanol solution of different surface tensions. The mean critical wetting surface tension of coal particles (y¯) obtained from the distribution shows that in general the hydrophobicity of coal particles decreases upon oxidation and that low-rank coals are more susceptible to oxidation than high-rank coals. The increase in y¯ can be correlated quite well with the oxygen uptake during oxidation and the acidic oxygen function group concentration on coal surface, and with the water retention capacity and the salt flotation yield of coals. This study further demonstrates that y¯c of coal can be used as a reliable parameter for correlating the wetting behavior of coals with their composition, rank and degree of oxidation and for predicting the behavior of coal particles in fine coal beneficiation.