Determination of complex formation constants of neptunium(V) with propionate and lactate in 0.5–2.6 m NaCl solutions at 22–60°C using a solvent extraction technique - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Article Dans Une Revue Radiochimica Acta Année : 2019

Determination of complex formation constants of neptunium(V) with propionate and lactate in 0.5–2.6 m NaCl solutions at 22–60°C using a solvent extraction technique

Résumé

Natural clay rocks like Opalinus (OPA) and Callovo-Oxfordian (COx) clay rock are considered as potential host rocks for deep geological disposal of nuclear waste. However, small organic molecules such as propionate and lactate exist in clay rock pore water and might enhance Np mobility through a complexation process. Therefore, reliable complex formation data are required in the frame of the Safety Case for a nuclear waste repository. A solvent extraction technique was applied for the determination of NpO+2 complexation with propionate and lactate. Extraction was conducted from isoamyl alcohol solution containing 10−3 M TTA and 5 · 10−4 M 1,10-phenanthroline. Experiments were performed in 0.5–2.6 m NaCl solutions at temperatures ranging from 22 to 60 °C. Formation of 1:1 Np(V) complexes for propionate and lactate was found under the studied conditions. The SIT approach was applied to calculate equilibrium constants β°(T) at zero ionic strength from the experimental data. Log β°(T) is found linearly correlated to 1/T for propionate and lactate, evidencing that heat capacity change is near 0. Molal reaction enthalpy and entropy (ΔrH∘m and ΔrS∘m) could therefore be derived from the integrated van’t Hoff equation. Data for log β° (298.15 K) are in agreement with literature values for propionate and lactate. Np(V) speciation was calculated for concentrations of acetate, propionate and lactate measured in clay pore waters of COx. In addition, the two site protolysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) model was applied to quantitatively describe the influence of Np(V) complexation on its uptake on Na-illite, a relevant clay mineral of OPA and COx.

Domaines

Chimie
Fichier principal
Vignette du fichier
2019-Vasiliev et al. (Radiochim. Acta).pdf (1.55 Mo) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)
Loading...

Dates et versions

insu-02270560 , version 1 (25-10-2019)

Identifiants

Citer

Aleksandr N. Vasiliev, Nidhu L Banik, Remi Marsac, Stepan Kalmykov, Christian M. Marquardt. Determination of complex formation constants of neptunium(V) with propionate and lactate in 0.5–2.6 m NaCl solutions at 22–60°C using a solvent extraction technique. Radiochimica Acta, 2019, 107 (7), pp.623-634. ⟨10.1515/ract-2019-3107⟩. ⟨insu-02270560⟩
76 Consultations
160 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More