Application of surface complexation models for radionuclide adsorption

This report discusses activity in two areas: an evaluation of methodologies currently used for the physical and chemical characterization of metal oxide and hydroxide adsorbents and the sensitivity of the various surface complexation models' adsorbent input parameters for describing adsorption. The report describes the relative merits of three surface complexation models (SCM), procedures to estimate values of the model parameters from titration data and what is required of experimental titration data sets. The ultimate goal is to determine how and whether SCMs can successfully describe adsorption of contaminants from disposed nuclear wastes in natural soils and sediment. This study's results help clarify the applicability of SCMs, particularly with respect to their sensitivity to input parameters. A method is presented by which unique, best fit values for these parameters may be obtained. An appendix is provided that reviews methods for determining surface area, site density, particle size distribution and pore structure. 17 refs., 13 figs., 23 tabs.