Abstract: Three kinds of craft waste liquids, which are by-products in the pulp industry and contain much lignin,were used as dispersing additives for preparing Horonai coal CWM (coal water mixture). The experiments showed that the CWM exhibited the lowest viscosity when it was diluted with an appropriate amount of water with the waste eiquids added. The experim ents also indicated that the maximum coal concentr ation in the pr act ically applicable CWMs w hose appar ent v iscosity has to be below 1000 m Pa·s incr eased fro m 56.5% to 62.5% (mass fraction), and 56.5% is the maximum coal mass fraction of the CWM prepared without additives. These data show the effectiveness of the waste liquids as the additives for preparing CWMs. The zeta potential of coal particles in the CWMs changed with the addition of lignin. From the change, the steric repulsion effect of the lignin adsorbed on the coal particles is concluded to be mainly responsible for the CWM dispersion. The waste liquids contain less sulfur than PSSNa(polystyrene sulfonate sodium salt), a typical dispersant which is currently used for preparing the commercial CWM, when the sulfur content in the unit mass of the solid matters within the waste liquids is compared with that in unit mass of PSSNa. This fact suggests that the waste liquids are more advantageous than PSSNa as far as air pollutants are concerned.

Key words: Pulp waste liquids, Lignin, CWM, Viscosity, ζ-Potential