The effects of phosphate on uranium adsorption to goethite-coated sand

The purpose of this investigation is to describe the effects of phosphate on U(VI) adsorption onto Fe-coated subsurface materials based on our experimental data. Previously, Barnett et al. (2002) reported that a model independently developed to describe U(VI) adsorption to synthetic ferrihydrite can be successfully applied to predict U(VI) adsorption to heterogeneous, iron oxide-containing subsurface media. In this investigation we used goethite-coated sand to mimic natural Fe-coated subsurface materials. U(VI) adsorption onto goethite-coated sand is studied in batch experiments as a function of pH in systems closed to the atmosphere, in the presence and absence of added phosphate. A surface complexation model (SCM) is used to model the data under a range of conditions. (orig.)