THERMODYNAMIC METHODS FOR ANALYSIS OF ADSORPTION DATA OF ORGANIC-COMPOUNDS AT ELECTRIFIED INTERFACES

The thermodynamic methods used for analysis of adsorption data at charged interfaces are reviewed critically. It is shown that the conventional methods depend the validity of their results upon the choice of the molecular model of the adsorbed layer. For this reason, contradictory conclusions may be drawn. A new thermodynamic approach which is free from the above shortcoming is described. In particular, it is shown that all the adsorption parameters, including that of size ratio, can be obtained on the basis of purely thermodynamic arguments without any reference to molecular models. Thus, the popular Frumkin and Bennes isotherms are proved to be valueless. It is also shown that useful information about the adsorption process and the interfacial interactions can be gained only when the adsorption parameters are interpreted by means of up-to-date molecular models for charged interfaces. The field effect and the physical content of the various adsorption parameters are examined. Finally, an analysis of the accuracy of the experimental data needed for the complete application of the new thermodynamic approach is also presented and discussed.