EFFECT OF AIR OXIDATION ON THE FLOATABILITY OF BITUMINOUS COALS - DIFFUSE REFLECTANCE INFRARED FOURIER-TRANSFORM (DRIFT) SPECTROSCOPIC ANALYSIS

The effect of induced air oxidation on the wettability behavior of coal was examined by studying its Hallimond tube flotation response and was correlated to the changes in organic moieties. Two different bituminous coals, Upper Freeport (PA) and Illinois No 6 seams, were examined for their flotation response to treatment by air heating for 24 and 72 h at 200°C. Although there was a sharp decrease in the floatability of coals after 24 h of heating, no further drop was observed beyond this time interval. Analysis of organic groups, by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, indicated almost complete disappearance of aliphatic CH groups by oxidation to carbonyl groups upon heating in air. However, there was no noticeable effect of heating, even for 72 h, on aromatic CH and CC groups. Initial decrease in floatability was attributed to the loss in hydrophobicity contributed by the aliphatic CH groups and the residual floatability to aromatic CH and CC groups which were not susceptible to oxidation at the temperature used. © 1990.