why I did ask the question is because I have seen some thermodynamic data reports recently for the adsorption of heavy metal ions as high as 1,000 J/mol for entropy and up to 900 kJ/mol for Gibbs free energy. Is this really normal?
Sure, for example Gibbs Isoterm provides the data for maximum value of surfactants adsorbed at the surfaces. Any further increase in concentation of surfactants in the solution, does not affect adsorbtion.