Surface chemical study in CWM was made with 20 kinds of raw coals and their chars made by heating on the stand point of functional groups on their surfaces, specially carboxyl group.
Carboxyl group has, unlike phenolic hydroxyl group, a strong influence on viscosity and water adsorp-tion characteristics, which may be deducible from the carboxyl content or zeta potential closely correlated with this content.
Carboxylic acid group is a highly active site and is converted to the salt form by exchange with ca-tions, such as Na+, K+, Ca2+ and Mg2+, inducing marked rise of pH and decline of zeta potential.
