I. Introduction. Background. Focus of the review. Review procedure and results. The NEA-TDB data base system. Presentation of the selected data. II. Standards and Conventions. Symbols, terminology and nomenclature. Units and conversion factors. Standard and reference conditions. Fundamental physical constants. III. Selected Uranium Data. IV. Selected Auxiliary Data. V. Discussion of Data Selection. Elemental uranium. Aqua ions. Oxide, hydride and hydroxide species. VI. Discussion of Auxiliary Data Selection. Reference list. Authors list. Formula list. Discussion of selected references. Ionic strength corrections. Assigned uncertainties. The estimation of entropies.

Chemical thermodynamics of uranium

Uranium(VI) adsorption to ferrihydrite: Application of a surface complexation model

Bacterial toxicity comparison between nano- and micro-scaled oxide particles.

The aqueous geochemistry of the rare-earth elements and yttrium

Rare earth elements in hydrothermal systems: Estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures

Structure of the hydrated dioxouranium(VI) ion in aqueous solution. An x-ray diffraction and proton NMR study

The complex formation in the system UVI–H2O–CO2(g) was studied by measuring the solubility of UO2(CO3)(s) as a function of the CO2 pressure and the hydrogen-ion concentration. The measurements were made at 25 °C, by using two different ionic media, 0.5 and 3 mol dm–3 NaClO4, respectively. The equilibrium constants for the following reactions were determined. Interaction UO2(CO3)(s)⇌ UO22++ CO32– Ks,o UO22++tCO32–⇌ UO2(CO3)t, t= 1–3 βt,1 3UO22++ 6CO32–⇄[(UO2)3(CO3)6]6–β6,3 coefficients Iµ(i,j) for the various uranium species with ClO4–(or Na+) were determined by using the Bronsted, Guggenheim, Scatchard specific ion-interaction theory. By using these and equilibrium data from the literature, we propose the following set of ‘best’ estimates of equilibrium constants, referred to the pure water reference state: log Ks,o=–14.4 ± 0.1, log β1,1= 9.5 ± 0.2, log β2,1= 16.6 ± 0.2, log β3,1= 21.3 ± 0.2, and log β6,3= 53.4 ± 0.8.

Studies on metal carbonate equilibria. Part 10. A solubility study of the complex formation in the uranium(VI)–water–carbon dioxide (g) system at 25 °C

Potentiometric measurements with a glass electrode combined with solubility determinations of CO/sub 2/(g) have indicated that, at 25/sup 0/C in 3 M NaClO/sub 4/ medium with (U(VI)) < 0.05 M and log (HCO/sub 3//sup -/) greater than or equal to -1.2, the prevailing form of uranium (VI) is the species UO/sub 2/(CO/sub 3/0/sub 3//sup 4 -/ (= UO/sub 2/(OH)/sub 6/(CO/sub 2/)/sub 2//sup 4 -/). On acidification of UO/sub 2/(CO/sub 3/)/sub 3//sup 4 -/, and before solid uranyl carbonates start to precipitate, a polynuclear complex (UO/sub 2/0/sub 3/(CO/sub 3/)/sub 6//sup 6 -/ (= UO/sub 2/)/sub 3/(OH)/sub 12/(CO/sub 2/)/sub 6//sup 6 -/) was found to form according to 3UO/sub 2/(CO/sub 3/)/sub 3//sup 4 -/ + 3CO/sub 2/(g) + 3H/sub 2/O reversible (UO/sub 2/)/sub 3/(CO/sub 3/)/sub 6//sup 6 -/ + 6HCO/sub 3//sup -/ with the equilibrium constant, log *..beta../sub 3,12,6/ = -6.43 +- 0.08. No evidence for the species UO/sub 2/(CO/sub 3/)/sub 2//sup 2 -/ or mixed species (UO/sub 2/)/sub p/(OH)/sub q/(CO/sub 3/)/sub r/ was obtained in the experimental range investigated: 10/sup -3/ less than or equal to (U(VI)) less than or equal to P/sub CO/sub 2// less than or equal to 1 atm, and -3.0 less than or equal to log (HCO/submore » 3//sup -/) less than or equal to -0.7. The /sup 13/C NMR spectra of the two complexes indicate the presence of three equivalent groups in the mononuclear complex and two different carbonate sites with the ratio 1:2 between the integrated intensities in the trinuclear complex. The NMR data are compatible with a structure containing both bridging and terminal carbonate groups.« less

The first acidification step of the tris(carbonato)dioxouranate(VI) ion, UO2(CO3)34-

In this study, macroscopic and spectroscopic data were combined to develop a surface complexation model that describes the acid-base properties of Bacillus subtilis. The bacteria were freeze-dried and then resuspended in 0.1 M NaCl ionic medium. Macroscopic measurements included potentiometric acid-base titrations and electrophoretic mobility measurements. In addition, ATR-FTIR spectra of wet pastes from suspensions of Bacillus subtilis at different pH values were collected. The least-squares program MAGPIE was used to generate a surface complexation model that takes into account the presence of three acid-base sites on the surface: tripple bond COOH, tripple bond NH+, and tripple bond PO-, which were identified previously by XPS measurements. Both potentiometric titration data and ATR-FTIR spectra were used quantitatively, and electrostatic effects at the charged bacterial surface were accounted for using the constant capacitance model. The model was calculated using two different approaches: in the first one XPS data were used to constrain the ratio of the total concentrations of all three surface sites. The capacitance of the double layer, the total buffer capacity, and the deprotonation constants of the tripple bond NH+, tripple bond POH, and tripple bond COOH species were determined in the fit. A second approach is presented in which the ratio determined by XPS of the total concentrations of tripple bond NH+ to tripple bond PO- sites is relaxed. The total concentration of tripple bond PO- sites was determined in the fit, while the deprotonation constant for tripple bond POH was manually varied until the minimization led to a model which predicted an isoelectric point that resulted in consistency with electrophoretic mobility data. The model explains well the buffering capacity of Bacillus subtilis suspensions in a wide pH range (between pH=3 and pH=9) which is of considerable environmental interest. In particular, a similar quantitative use of the IR data opens up possibilities to model other bacterial surfaces at the laboratory scale and help estimate the buffering capacity of carboxylate-containing compounds in natural samples.

Modeling the acid-base properties of bacterial surfaces: A combined spectroscopic and potentiometric study of the gram-positive bacterium Bacillus subtilis.

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Diego Ferri

Papers

Structure of the hydrated dioxouranium(VI) ion in aqueous solution. An x-ray diffraction and proton NMR study

Studies on metal carbonate equilibria. Part 10. A solubility study of the complex formation in the uranium(VI)–water–carbon dioxide (g) system at 25 °C

The first acidification step of the tris(carbonato)dioxouranate(VI) ion, UO2(CO3)34-

Modeling the acid-base properties of bacterial surfaces: A combined spectroscopic and potentiometric study of the gram-positive bacterium Bacillus subtilis.

Studies on metal carbonate equilibriums. 3. the lanthanum(iii) carbonate complexes in aqueous perchlorate media