Abstract This paper describes the adsorption kinetics and isotherms for cationic and anionic surfactants on coal surfaces. Both types of surfactants adsorb significantly rapidly; although the cationic surfactant achieved much higher levels of adsorption than the anionic one. The adsorption isotherms are of typical Langmuir type and employed for calculation of free energies. The results indicate that adsorption occurs through hydrophobic interaction in addition to electrostatic attraction between the surfactant molecules and the coal surface. Surfactant adsorption is shown to be a significant factor in the improved dewatering of coal particles. These improvements have been attributed to the changes which surfactant adsorption causes in the wetting characteristics of the coal surfaces. The results obtained are evaluated in terms of surface effects and by reference Laplace–Young equation. Furthermore, this equation has been used to quantify dewatering phenomena.