title: Uranium(VI) adsorption and surface complexation modeling onto background sediments from the F-Area Savannah River Site.
abstract: The mobility of an acidic uranium waste plume in the F-Area of Savannah River Site is of great concern. In order to understand and predict uranium mobility, U(VI) adsorption experiments were performed as a function of pH using background F-Area aquifer sediments and reference goethite and kaolinite (major reactive phases of F-Area sediments), and a component-additivity (CA) based surface complexation model (SCM) was developed. Our experimental results indicate that the fine fractions (≤45 μm) in sediments control U(VI) adsorption due to their large surface area, although the quartz sands show a stronger adsorption ability per unit surface area than the fine fractions at pH < 5.0. Kaolinite is a more important sorbent for U(VI) at pH < 4.0, while goethite plays a major role at pH > 4.0. Our CA model combines an existing U(VI) SCM for goethite and a modified U(VI) SCM for kaolinite along with estimated relative surface area abundances of these component minerals. The modeling approach successfully predicts U(VI) adsorption behavior by the background F-Area sediments. The model suggests that exchange sites on kaolinite dominate U(VI) adsorption at pH < 4.0, goethite and kaolinite edge sites cocontribute to U(VI) adsorption at pH 4.0-6.0, and goethite dominates U(VI) adsorption at pH > 6.0.
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
authors.forename: Wenming
authors.initials: W
authors.lastname: Dong
authors.forename: Tetsu K
authors.initials: TK
authors.lastname: Tokunaga
authors.forename: James A
authors.initials: JA
authors.lastname: Davis
authors.forename: Jiamin
authors.initials: J
authors.lastname: Wan
mesh_terms: D000327:Adsorption; D019015:Geologic Sediments / Q000737:chemistry*; D005845:Georgia; D060587:Groundwater / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000737:chemistry; D007616:Kaolin / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D008956:Models, Chemical; D011791:Quartz / Q000737:chemistry; D011848:Radioactive Pollutants / Q000032:analysis* / Q000737:chemistry; D014501:Uranium / Q000032:analysis* / Q000737:chemistry
chemical_list: D058085:Iron Compounds; D008903:Minerals; D011848:Radioactive Pollutants; C094886:goethite; D011791:Quartz; D007616:Kaolin; D014501:Uranium