Chemical attenuation reactions of selenium; Final report
- Battelle, Pacific Northwest Laboratories, Richland, WA (United States)
This report summarizes research on the geochemical behavior of Se present in utility coal-combustion wastes. Laboratory experiments quantified select geochemical reactions that control the concentrations of selenite (SeO{sub 3}{sup 2{minus}}) and selenate (SeO{sub 4}{sup 2{minus}}) in soil solutions and groundwater and determined the magnitude and mechanisms of chemical attenuation of these species in soils and subsurface materials. Thermodynamic data, equilibrium constants, and modeling procedures were developed that to utilities to make improved predictions of the mobility of Se species from ponded and dry landfill sites. An adsorption-constant database for selenite and selenate on common soil minerals was developed. The database, which can be used to estimate the extent of Se attenuation by adsorption in utility soils, was used to determine the specific mineral phases control the adsorption of selenite (Fe oxides) and selenate (Al oxides). Solubility studies were performed with two Se solid phases that may form in the environment [BaSeO{sub 4}(c) and Fe{sub 2}(SeO{sub 3}){sub 3}{lg_bullet}6H{sub 2}0(c)] to establish upper limits on Se concentrations. New thermodynamic data were developed to allow prediction of aqueous Se concentrations where these phases may exist. Eleven soil and subsurface materials, collected nationally and representative of properties frequently encountered at waste sites, were used in experiments involving adsorption of selenite and selenate to assess their potential for Se chemical attenuation and to determine chemical and mineralogic factors that control Se adsorption. Selenite was far more strongly adsorbed by the geologic materials than the selenate. The adsorption of both Se species depended on the type of natural materials and showed positive correlation with Fe and Al oxides associated with particle surfaces. Procedures were developed to predict Se adsorption from comprehensive chemical and mineralogic characterization data.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (United States); Battelle Pacific Northwest Lab., Richland, WA (United States)
- Sponsoring Organization:
- Electric Power Research Inst., Palo Alto, CA (United States)
- OSTI ID:
- 140910
- Report Number(s):
- EPRI-TR--103535
- Country of Publication:
- United States
- Language:
- English
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