The role of surfactant adsorption in the improved dewatering of fine coal

This paper describes the adsorption kinetics and isotherms for cationic and anionic surfactants on coal surfaces. Both types of surfactants adsorb sig nificantly rapidly; although the cationic surfactant achieved much higher l evels of adsorption than the anionic one. The adsorption isotherms an of ty pical Langmuir type and employed for calculation of free energies. The resu lts indicate that adsorption occurs through hydrophobic interaction in addi tion to electrostatic attraction between the surfactant molecules and the c oal surface. Surfactant adsorption is shown to be a significant factor in t he improved dewatering of coal particles. These improvements have been attr ibuted to the changes which surfactant adsorption causes in the wetting cha racteristics of the coal surfaces. The results obtained an evaluated in ter ms of surface effects and by reference Laplace-Young equation. Furthermore, this equation has been used to quantify dewatering phenomena. (C) 1999 Els evier Science Ltd. All rights reserved.