Thermodynamics and macro-kinetics of adsorption

In Chapter 1 we briefly described an interface as a layer with uncompensated intermolecular forces. The thermodynamics of a liquid interfaces covered with a soluble or insoluble monolayer layer has been describe in detail by many other competent authors and we want to present only the thermodynamic basis needed for the subsequent chapters of this book. Let us consider the interface between water and air. The specific properties of the bulk water, e.g. the freezing point, boiling point, vapour pressure, viscosity, cluster formation and hydrophobic bonds, are well described by long and short-range intermolecular forces and strong and weak intramolecular forces. Israelachvili recently (1992) remarked in a short note on the usefulness of this classification, although it is not clear whether the same interaction is counted twice or two normally distinct interactions are strongly coupled. 

Nevertheless, we have to work with the same intermolecular forces as in chemistry. Additionally, in surface and colloid chemistry interactions of macroscopic bodies exist and the summation of all intermolecular forces leads to another force due to a specific force-distance function. First there are the well-known van der Waals forces which are attractive and decay due the power of sixth. Other attractive forces are  

Another class of interacting forces are the so-called chemical forces (Prausnitz 1969). In contrast to the physical forces these forces are counterbalanced. Typical examples are the covalent bonds, electron donor-acceptor interactions, acidic solute - basic solvent interactions. Association and solvatation are effects well-known to every chemist. 

Following the concept of Tanford (1980), we find interactions of surfactant molecules in aqueous solution encouraging the formation of micelles and adsorption layers at a liquid 

In the case of interacting molecules with distances short enough for the electronic shells to overlap, Mie (1903) suggested a relationship with an empirical constant and a certain decay law of high power against distance. Later, on the basis of Mie s equation and the van der Waals law h Lennard-Jones (1936) derived an intermolecular pair potential 

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