Np(V) complexation with propionate in 0.5-4 M NaCl solutions at 20-85 °C
Low molecular weight organics (LMWO; e.g. acetate, propionate, lactate) can significantly impact the speciation and mobility of radionuclides in aqueous media. Natural clay rock formation, considered as a potential host rock for nuclear waste disposal, can contain a significant amount of organic mat...
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| Main Authors: | , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
22 Jan 2015
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| In: |
Dalton transactions
Year: 2015, Volume: 44, Issue: 8, Pages: 3837-3844 |
| ISSN: | 1477-9234 |
| DOI: | 10.1039/C4DT03688C |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1039/C4DT03688C Verlag, lizenzpflichtig, Volltext: https://pubs.rsc.org/en/content/articlelanding/2015/dt/c4dt03688c 
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| Author Notes: | Aleksandr N. Vasiliev, Nidhu L. Banik, Rémi Marsac, Daniel R. Froehlich, Jörg Rothe, Stepan N. Kalmykov, Christian M. Marquardt |
| Summary: | Low molecular weight organics (LMWO; e.g. acetate, propionate, lactate) can significantly impact the speciation and mobility of radionuclides in aqueous media. Natural clay rock formation, considered as a potential host rock for nuclear waste disposal, can contain a significant amount of organic matter. There are less thermodynamic data reported for the complexation of pentavalent actinides with LMWO, especially under elevated temperature conditions, relevant for assessing the long-term safety of disposal options for heat-producing high-level nuclear waste. In the present study, the complexation of Np(V) with propionate is studied using spectroscopic techniques in 0.5-4 M NaCl solutions by systematic variation of the ligand concentration and temperature. Slope analysis shows the formation of the 1 : 1 NpO2-propionate complex (NpO2Prop). The local structure of the NpO2-propionate complex is determined by extended X-ray absorption fine structure spectroscopy, the results of which suggest that propionate binds to Np(V) in a bidentate mode. Using the specific ion interaction theory (SIT), the stability constant at zero ionic strength and 25 °C is determined as log β°1,1 = 1.26 ± 0.03. The stability constants increase continuously with increasing temperature between 20 and 85 °C. The log β0 values are linearly correlated with the reciprocal temperature, indicating ΔrH0m = const. and ΔrC0p,m = 0, allowing the calculation of ΔrH0m and ΔrS0m for the formation of the NpO2-propionate complex using the integrated van't Hoff equation. The thermodynamic evaluation indicates that the reaction is endothermic and entropy driven. |
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| Item Description: | Gesehen am 08.07.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1477-9234 |
| DOI: | 10.1039/C4DT03688C |