Conceptual model for the adsorption of organic compounds from the gas phase to liquid and solid surfaces

Adsorption of organic pollutants from the gas phase to ambient surfaces has a great impact on the environmental mobility of these compounds. In a recent paper, gas phase adsorption coefficients for different compounds and surfaces have successfully been predicted based on thermodynamic parameters (surface free energies) without the use of any empirical fitting. However, the surface free energies required for these calculations are only known for a limited number of adsorbates and surfaces, these parameters can be substituted by others (in p(L)(o), beta, and alpha) that are tabulated for a wide range of compounds. Validation of this extended model with experimental data shows good results. At the same time, the conceptual understanding of the adsorption equilibrium in terms of van der Waals and Lewis acid-base (electron donor-acceptor) interactions, which is provided by the original model, remains unaltered. This paper is concluded by a discussion of our current knowledge of the surface parameters that are additionally required for the calculations.