THERMODYNAMICS OF ADSORPTION FROM SOLUTION - EXPERIMENTAL AND FORMAL ASSESSMENT OF THE ENTHALPIES OF DISPLACEMENT

This paper analyzes the operational ways to derive well-defined enthalpies of displacement from the various types of calorimetric experiments available today.These involve either immersion of a dry adsorbent into a liquid or displacement of the preadsorbed solvent by a solute. The latter experiment may in turn be carried out either in a batch or in a flow-through arrangement. In each case, both dilution and adsorption contributions are separated and the problem of the choice of the reference state is examined. Equations are obtained either for dilute solutions or for mixtures. In the case of dilute solutions, the possible simplications are considered. The enthalpy of displacement derived from the shift of the adsorption isotherms with temperature, by applying the "isosteric" method, is compared with that derived from calorimetric experiments. © 1990.