Enthalpies of adsorption of sodium dodecyl sulphate and O-n-octyltetraethylene glycol from aqueous solutions onto graphitised carbon

Abstract

A comparison has been made of the adsorption of a non-ionic and an ionic surfactant from aqueous solution on to graphitised carbon. Adsorption enthalpies determined calorimetrically have been combined with adsorption isotherms to yield differential heats of adsorption. The ionic compound was found to adsorb with a negative differential heat at all coverages studied, whereas the non-ionic compound adsorbed in three clearly distinguishable stages which corresponded to exothermic, athermal and endothermic processes. A model is suggested to account for these observations.