Effect of Oxygen Functional Groups on the Surface Properties and Flotation Response of Fine Coal, Comparison of Rank with Oxidation.

The surface properties and flotation response of coal samples of different rank correspond to results from similar experiments for coal samples with different degrees of oxidation. Three principal types of oxygen-containing functional groups (C = O, C-O, O = C-O), were detected at the surface of low rank coals and oxidized coals by XPS, complementing results of previous researchers reported in the literature. The hydroxylation of these polar oxygen groups to C-OH groups and O = C-OH groups seems to account for the observed decrease in hydrophobic character and reduced flotation recovery. Hydration of the coal surface is facilitated at these hydroxylated sites by hydrogen bonding with interfacial water molecules. [ABSTRACT FROM AUTHOR]