Specific and nonspecific cation adsorption to clays: solution concentrations and surface potentials.

A model for cation adsorption to negatively charged surfaces is developed by taking into account specific cation binding to the surface sites and adsorption in the double layer region. Equations are given for any combination of mono and divalent cations in solution and for one type of binding site. Variations in solution concentrations of cations due to adsorption are explicitly included in the model in the framework of an iterative procedure. The results indicate that a Langmuir type of adsorption isotherm may represent the data over a certain range of cation concentrations. -from Author