GEOC 39 |
| Michael L. Coleman1, Chia-chen Chen2, and Lynn E. Katz2. (1) Department of Civil Engineering, University of Texas-Austin, 1 University Station C1786, Austin, TX 78712, (2) Department of Civil Engineering, University of Texas, Austin, TX 78712 |
| The fate and transport of toxic metal ions in natural and engineered systems is often controlled by adsorption and precipitation processes. Surface complexation models (SCMs) represent one of the most promising techniques for describing metal ion sorption onto soil minerals. While these models are capable of accounting for the effects of pH, solution ionic strength, competing solutes, ternary complex formation and solid solution formation, they often fail to predict adsorption behavior over large ranges of these parameters. For example, the ability to predict ionic strength effects and solid solution formation is often metal ion and mineral dependent. Previous research has shown that many divalent metal ions form hydrotalcite or silicate precipitates with aluminum and silica minerals and clays. Our previous modeling efforts have incorporated surface precipitation into surface complexation formation for aluminum oxides by using x-ray absorption spectroscopy to guide the model development. In this research we have extended our surface complexation modeling of divalent metal ion sorption to silica oxides in the presence of different background electrolyte anions. To do this, we have applied a self-consistent thermodynamic database for the electrical double layer properties and the reaction equilibria. The results of these modeling efforts will be presented along with x-ray absorption spectroscopy data to support the modeling results. |
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Chemistry of Metals in Terrestrial and Aquatic Systems
1:30 PM-5:10 PM, Monday, March 29, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |