X-ray photoelectron spectroscopy was used to determine the
influence of liquid phase oxidation on the
surface structure of coals. The surface composition changes
(increase in sulfur and carbon content and
decrease in mineral matter amount), together with the content ratio of
N/C, prove the applicability of the
two-component model to describe the structure of coal. The mobile
phase contains sulfur but no nitrogen
compounds. Analysis of the C 1s peak shape enabled detailed
discussion of the formation of oxygen-containing surface groups, depending on the starting coal rank and
concentration and type of the oxidizing
solution.
This paper presents a quantitative characterization of the effects
of oxidiation on the surface of coal
based on water sorption measurements. Two coals of different rank
were examined before and after
oxidation with H2O2 and KMnO4.
A theoretical model describing sorption equilibria, as the effect
of
adsorption in submicropores and absorption in the elastic phase of
coal, was applied to evaluate structural
and enegetic parameters of the sorption systems. Oxidation results
in a noticeable increase in the adsorption
capacity of the studied coals and practically does not affect the
absorption. This is due to creation of new
oxygen-containig surface groups on the coal surface, as was shown by
XPS measurements. A significant
increase in the adsorption energy together with much smaller changes in
concentration of water molecules
on the coal surface was seen. This suggests an increase in the
number of double bonds between adsorbed
water molecules and oxygen-containig surface groups.
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