ABSTRACT
A number of processes can occur during sorption, including absorption by diffusion into the solid matrix or adsorption at the surface/water interface by surface complexation, surface polymerization, and surface precipitation. This chapter reviews the type of spectroscopic information that is needed to use surface complexation models (SCMs) and recent spectroscopic studies which have provided this information. By way of introduction, a brief review of divalent metal cation sorption and the dependence of sorption processes on solution conditions is provided. Empirical modeling approaches which require conditional constants, such as the linear partitioning coefficient are discussed, in view of their current widespread use in contaminant transport models, to point out their limitations compared with SCMs. Finally, a comparison among three SCMs, the nonelectrostatic model, the diffuse layer model, and the triple layer model is given illustrating the relative capabilities of the three SCMs for predicting sorption over wide ranges of solution conditions.
