Adsorption of ethoxylated sulfonate and nonionic homologs on coal

The adsorption of ethoxylated sulfonates and nonionics of the same ethoxylation number on a low-ash coal has been studied. The surfactant adsorption has been investigated as a function of concentration, pH, temperature, and ionic strength for three homologs. The zeta potential of the coal particles and the surface tension of the supernatants have been concurrently determined to elucidate the orientation of surfactant molecules on the coal surface as well as the mechanism of adsorption. The adsorption data are utilized to calculate thermodynamic parameters such as the free energy of adsorption and the isoteric heats of adsorption.