Investigation of U(VI) desorption behavior from natural sediment, Oak Ridge

Abstract

Investigation of U(VI) desorption from the natural sediment of Oak Ridge Field Research Center saprolite is of great importance to predict the fate and transport of U(VI) in the subsurface environment. After treatment by the dithonite- citrate-bicarbonate method, only 20% of U(VI) was extracted by 0.1 mol/L HNO3 solution, indicating that the predominate adsorbed carrier of U(VI) in natural sediment was iron (hydr)oxides. Further evidence collected through a high resolution TEM investigation such as goethite observed in clay minerals. The desorption of U(VI) from PRFRC saprolite was satisfactorily fitted by surface complexation modeling at a low NaHCO3 concentration starting from 0.001 to 0.1 mol/L, whereas appreciable over-estimation was observed at high concentrations of NaHCO3. The uncertainty analysis method used in this study was an expanded uncertainty analysis method, and estimates with a 95% confidence interval (c) were obtained for these test data points. These observations revealed that the goethite with clay minerals played the vital role in U(VI) sorption and desorption behaviors in subsurface sediments.