Speciation simulation and sorption mechanism of 238Pu in radioactive waste repository lithosphere
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Chao Chen
,
Song Yang
Abstract
The assessment of the migratory and environmental behavior of radioactive nuclides escaping from waste treatment facilities heavily relies on the use of numerical models capable of simulating and characterizing all significant processes of nuclides in complex geological environments. Adsorption models typically encompass the chemical properties of the nuclides themselves and their chemical reactions with the surrounding environment, as well as processes such as ion exchange or physical adsorption. These processes must be taken into consideration in the long-term safety assessment of radioactive waste repositories. The redox-sensitive nuclide 238Pu, a critical member among transuranic elements, exhibits a diverse range of aqueous forms, and concurrently, it possesses high toxicity. The chemical behavior of 238Pu shows strong spatial variability with changes in environmental conditions. In this study, we constructed a theoretical model for the migration of nuclides in soil and groundwater environments through indoor static batch experiments and hydrogeochemical simulations. Experimental methods were employed to dissect the micro-scale, irreversible adsorption reaction processes of nuclides and identify their primary existing forms. According to field measurements, the pH of groundwater was recorded as 7.48, with an Eh of 125.7 mV. Introducing a solid-to-liquid ratio of 1:10 g/mL in centrifuge tubes, we measured the radioactive nuclide concentration after achieving adsorption and desorption equilibrium, obtaining adsorption and desorption isotherms. The PHREEQC software was employed to investigate the changes in 238Pu forms under varying conditions of pH and redox potential. Field measurements provided groundwater pH and Eh values. The activity concentration of the nuclide was measured after reaching adsorption and desorption equilibrium. The results show that the adsorption isotherms of 238Pu differ from its desorption isotherms, indicating an irreversible adsorption-desorption process. Ion exchange and surface complexation were identified as the main modes of adsorption. PHREEQC simulations revealed that 238Pu primarily existed in forms such as tetravalent Pu(OH)4 and trivalent Pu(SO4)2 −, PuSO4 +. Pu(OH)4 accounted for the largest proportion (97%) in the groundwater solution system, while a minimal amount of pentavalent PuO2 + was present. Environmental factors, such as pH and the presence of ions like SO4 2− and HCO3 −, influenced the forms of 238Pu.
Acknowledgments
This work was supported by Ministry of Science and Technology National Key R&D Program (2020YFC1806600) and National Natural Science Foundation of China (U2267217, 42272295).
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Research ethics: The local Institutional Review Board deemed the study exempt from review.
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Author contributions: The authors have accepted responsibility for the entire content of this manuscript and approved its submission.
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Competing interests: The authors state no conflict of interest
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Research funding: This work was supported by Ministry of Science and Technology National Key R&D Program (2020YFC1806600) and National Natural Science Foundation of China (U2267217, 42272295).
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Data availability: The raw data can be obtained on request from the corresponding author.
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Articles in the same Issue
- Frontmatter
- Original Papers
- Speciation simulation and sorption mechanism of 238Pu in radioactive waste repository lithosphere
- Magnetic alginate supported potassium manganese ferrocyanide for the recovery of uranium from acidic wastewater
- Separation of ReO4−/TcO4− from simulated radioactive waste liquid by a novel series of anion exchange resins
- Technetium-99m radiolabeling through conjugation with l,l-ethylene dicysteine chelator of a trimethoxylated flavone and its bioevaluation in rat with induced C6 glioma tumor as a new cancer diagnostic agent
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- Impact of gamma irradiation on phytochemical composition, and biological activities of Lepidium sativum seeds extract
Articles in the same Issue
- Frontmatter
- Original Papers
- Speciation simulation and sorption mechanism of 238Pu in radioactive waste repository lithosphere
- Magnetic alginate supported potassium manganese ferrocyanide for the recovery of uranium from acidic wastewater
- Separation of ReO4−/TcO4− from simulated radioactive waste liquid by a novel series of anion exchange resins
- Technetium-99m radiolabeling through conjugation with l,l-ethylene dicysteine chelator of a trimethoxylated flavone and its bioevaluation in rat with induced C6 glioma tumor as a new cancer diagnostic agent
- The effect of gamma rays and stearic acid on calcium carbonate and its impact on the properties of epoxy-based composites
- Impact of gamma irradiation on phytochemical composition, and biological activities of Lepidium sativum seeds extract
