Ideal adsorbed phase model for adsorption of phenolic compounds on activated carbon

The applicability of the ideal adsorbed phase (IAP) model to the adsorption of selected phenolic organics on activated carbon has been studied. Experimental adsorption data were obtained as a function of solution pH and temperature for phenol and aniline, and characterized with the model. The characterizations include the effects of solvent adsorption, a factor that has been consistently neglected in the past. A critical analysis of the IAP model shows that a good fit of the surface excess isotherm data does not ensure that the underlying assumptions of the model are applicable. It has been shown for both phenol and aniline that while the surface excess data may be well characterized, there are significant discrepancies between the experimental and predicted values of the free immersion energy. Also, while the surface free immersion energy of phenol is only a function of surface coverage, for aniline it is also a function of pH and temperature. The importance of specifically accounting for the solvent as an adsorbing species in multicomponent systems has also been demonstrated. Predictions of the IAP model are shown to be significantly different in the presence and absence of water adsorption. (C) 1997 Elsevier Science Ltd.