Uranium(VI) Adsorption and Surface Complexation Modeling onto Background Sediments from the F-Area Savannah River Site

• Published in: Environmental science & technology 2012-02, Vol.46 (3), p.1565-1571
• Main Authors: Dong, Wenming, Tokunaga, Tetsu K, Davis, James A, Wan, Jiamin
• Format: Article
• Language: English
• Subjects: Adsorption; Applied sciences; Aquifers; Biological and physicochemical properties of pollutants. Interaction in the soil; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geologic Sediments - chemistry; Georgia; Groundwater - chemistry; Groundwaters; Hydrogen-Ion Concentration; Iron Compounds - chemistry; Kaolin - chemistry; Minerals; Minerals - chemistry; Models, Chemical; Natural water pollution; Pollution; Pollution, environment geology; Quartz - chemistry; Radioactive Pollutants - analysis; Radioactive Pollutants - chemistry; Rivers; Sediments; Soil and sediments pollution; Uranium; Uranium - analysis; Uranium - chemistry; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es2036256

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.