NEW CONCEPT FOR COAL-WATER MIXTURE STABILIZATION USING A POLYELECTROLYTE

The stabilization mechanism of Sodium Polystyrene Sulphonate (PSSNa) on coal water mixture (CWM) has been examined using the following colloid chemical concept. It is realized that the stabilization of the CWM is due to an increase in electrostatic repulsion between the coal particles and the electrostatic repulsion is influenced strongly by the concentration of metal cations, especially Ca2+ eluted from the coal surface. The adsorption isotherm of PSSNa on the coal surface indicates a weak affinity type and the desorption amount of PSSNa is tremendously small in compared with the amount of adsorption. This indicates that a lot of PSSNa adsorbed weakly has been eliminated from the surface in the pre-washing process of desorption experiment. Furthermore, it appears that the zeta-potential determined by the Acoustosizer for concentrated coal suspension shows higher values than the values determined by the usual electrophoresis, and that the high values hold for a wide range of salt concentrations in the medium. All these results indicate that much PSSNa is adsorbed weakly on the coal surface and the component plays a role in the stability character of CWM, where a large contribution of depletion stabilization effect can be expected.