Plutonium(IV) and (V) Sorption to Goethite at Sub-Femtomolar to Micromolar Concentrations: Redox Transformations and Surface Precipitation
| Autor: | Pihong Zhao, Mavrik Zavarin, Ross W. Williams, Ruth Kips, James D. Begg, Scott J. Tumey, Annie B. Kersting, Zurong R. Dai |
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| Rok vydání: | 2016 |
| Předmět: |
Goethite
010504 meteorology & atmospheric sciences Chemistry Precipitation (chemistry) chemistry.chemical_element Sorption General Chemistry 010501 environmental sciences 01 natural sciences Redox Plutonium Adsorption Oxidation state visual_art visual_art.visual_art_medium Environmental Chemistry High-resolution transmission electron microscopy Oxidation-Reduction 0105 earth and related environmental sciences Nuclear chemistry |
| Zdroj: | Environmental Science & Technology. 50:6948-6956 |
| ISSN: | 1520-5851 0013-936X |
| Popis: | Pu(IV) and Pu(V) sorption to goethite was investigated over a concentration range of 10(-15)-10(-5) M at pH 8. Experiments with initial Pu concentrations of 10(-15) - 10(-8) M produced linear Pu sorption isotherms, demonstrating that Pu sorption to goethite is not concentration-dependent across this concentration range. Equivalent Pu(IV) and Pu(V) sorption Kd values obtained at 1 and 2-week sampling time points indicated that Pu(V) is rapidly reduced to Pu(IV) on the goethite surface. Further, it suggested that Pu surface redox transformations are sufficiently rapid to achieve an equilibrium state within 1 week, regardless of the initial Pu oxidation state. At initial concentrations10(-8) M, both Pu oxidation states exhibited deviations from linear sorption behavior and less Pu was adsorbed than at lower concentrations. NanoSIMS and HRTEM analysis of samples with initial Pu concentrations of 10(-8) - 10(-6) M indicated that Pu surface and/or bulk precipitation was likely responsible for this deviation. In 10(-6) M Pu(IV) and Pu(V) samples, HRTEM analysis showed the formation of a body centered cubic (bcc) Pu4O7 structure on the goethite surface, confirming that reduction of Pu(V) had occurred on the mineral surface and that epitaxial distortion previously observed for Pu(IV) sorption occurs with Pu(V) as well. |
| Databáze: | OpenAIRE |
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