Quantifying differences in the impact of variable chemistry on equilibrium uranium(VI) adsorption properties of aquifer sediments
Environmental Science & Technology
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Abstract
Uranium adsorption-desorption on sediment samples collected from the Hanford 300-Area, Richland, WA varied extensively over a range of field-relevant chemical conditions, complicating assessment of possible differences in equilibrium adsorption properties. Adsorption equilibrium was achieved in 500-1000 h although dissolved uranium concentrations increased over thousands of hours owing to changes in aqueous chemical composition driven by sediment-water reactions. A nonelectrostatic surface complexation reaction, >SOH + UO22+ + 2CO32- = >SOUO2(CO3HCO3)2-, provided the best fit to experimental data for each sediment sample resulting in a range of conditional equilibrium constants (logKc) from 21.49 to 21.76. Potential differences in uranium adsorption properties could be assessed in plots based on the generalized mass-action expressions yielding linear trends displaced vertically by differences in logKc values. Using this approach, logKc values for seven sediment samples were not significantly different. However, a significant difference in adsorption properties between one sediment sample and the fines (<0.063 mm) of another could be demonstrated despite the fines requiring a different reaction stoichiometry. Estimates of logKc uncertainty were improved by capturing all data points within experimental errors. The mass-action expression plots demonstrate that applying models outside the range of conditions used in model calibration greatly increases potential errors.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Quantifying differences in the impact of variable chemistry on equilibrium uranium(VI) adsorption properties of aquifer sediments |
| Series title | Environmental Science & Technology |
| DOI | 10.1021/es202677v |
| Volume | 45 |
| Issue | 20 |
| Year Published | 2011 |
| Language | English |
| Publisher | ACS Publications |
| Contributing office(s) | Branch of Regional Research-Western Region, Toxic Substances Hydrology Program |
| Description | 8 p. |
| First page | 8733 |
| Last page | 8740 |
| Country | United States |
| State | Washington |
| County | Benton County |
| City | Richland |
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