Determination of formation constants and specific ion interaction coefficients for Ca$_n$UO$_2$(CO$_3$)$_3$^{(4−2n)−} complexes in NaCl solution by time-resolved laser-induced luminescence spectroscopy - Archive ouverte HAL Access content directly Journal Articles Dalton Transactions Year : 2020 ## Determination of formation constants and specific ion interaction coefficients for Ca_nUO_2(CO_3)_3$^{(4−2n)−}$ complexes in NaCl solution by time-resolved laser-induced luminescence spectroscopy

(1, 2) , (1, 2)
1
2
Pascal E. Reiller

Connectez-vous pour contacter l'auteur

#### Abstract

The formation constants of CaUO$_2$(CO$_3$)$_3$^{2−} and Ca_2UO_2(CO_3)_3(aq) were determined in NaCl medium at ionic strengths between 0.1 and 1 mol kg_w$^{−1}$ using time-resolved laser-induced luminescence spectroscopy (TRLS). Spectroluminescence titration of UO$_2$(CO$_3$)$_3$^{4−} complex by Ca^{2+} were conducted at atmospheric CO_2(g) and varying pH values in order to eliminate the eventual precipitation of both schoepite (UO_3 : 2H_2O) and calcite (CaCO_3) in aqueous solutions. To identify the stoichiometry of calcium, the slope analyses corrected by the Ringböm coefficient for UO_2(CO_3)_3$^{4−}$ relative to pH and CO$_2$(g)—instead of typical expression relative to UO$_2$^{2+} and CO_3$^{2−}$—was applied in this work. Satisfactory linear fits assessed the conditional stepwise formation constants in the range of ionic strength employed in this work, the values of which are in good agreement with literature data at comparable ionic strengths. Extrapolations to infinite dilution were realized in the framework of the specific ion interaction theory (SIT), also providing the evaluation of the specific ion interaction coefficients. The cumulative stability constants at infinite dilution was determined to be log$_{10}$ β°(CaUO$_2$(CO$_3$)$_3$^{2−}) = 27.20 ± 0.04 and log_{10} β°(Ca_2UO_2(CO_3)_3(aq)) = 30.49 ± 0.05, which are in good agreement with extrapolation proposed elsewhere in literature using a different extrapolation framework. The specific ion interaction coefficients were found to be ε(CaUO_2(CO_3)_3$^{2−}$,Na$^+$) = (0.29 ± 0.11) and ε(Ca$_2$UO$_2$(CO$_3$)$_3$(aq),NaCl) = (0.66 ± 0.12) kg$_w$ mol$^{−1}$. Integration of alkali metals into the ternary species may explain these positive and relatively large interaction coefficients. Implications on the speciation of uranium in clay groundwaters, representative of radioactive waste repositories, and in seawater are discussed.

### Dates and versions

cea-02419900 , version 1 (15-12-2020)

### Identifiers

• HAL Id : cea-02419900 , version 1
• DOI :

### Cite

Chengming Shang, Pascal E. Reiller. Determination of formation constants and specific ion interaction coefficients for Ca$_n$UO$_2$(CO$_3$)$_3$$^{(4−2n)−}$ complexes in NaCl solution by time-resolved laser-induced luminescence spectroscopy. Dalton Transactions, 2020, 49 (2), pp.466-481. ⟨10.1039/C9DT03543E⟩. ⟨cea-02419900⟩

### Export

BibTeX TEI Dublin Core DC Terms EndNote Datacite

59 View