Speciation of uranium: Compilation of a thermodynamic database and its experimental evaluation using different analytical techniques

UO22+-mediated ring contraction of pyrihexaphyrin: synthesis of a contracted expanded porphyrin-uranyl complex

“…Bart, Schelter, and co-workers have recently reported the ability of redox-active iminoquinone ligands to facilitate oxo-activation and reduction of U( vi ) to U( iv ) 54. Furthermore, in the presence of a reductant and proton source, the reduction of U( vi )O 2 2+ under anaerobic conditions to yield U( vi ) and water can occur 54,55…”

Speciation of Uranium and Plutonium From Nuclear Legacy Sites to the Environment: A Mini Review

“…Thermodynamic modeling of uranium species and its comparison with the experimental data that were obtained via direct non-destructive methods is necessary to investigate of uranium behavior at the contaminated sites. The use of different databases for the same water composition leads to substantial differences in modeling as was shown by Mühr-Ebert et al ( 2019 ). To clarify this, the researchers optimized the thermodynamic data using model calculations and laboratory tests by TRLFS, mass spectrometry, and extraction experiments under various model conditions (Mühr-Ebert et al, 2019 ).…”

Uranium migration through the Swiss Opalinus Clay varies on the metre scale in response to differences of the stability constant of the aqueous, ternary uranyl complex Ca<sub>2</sub>UO<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub>

“…In contrast, in a sorption experiment done for the same system (Joseph et al, 2011), a value of 30.55 for the logk of the neutral complex (Bernhard et al, 2001) was used in the speciation calculations leading to the neutral complex as predominant one. Both complexes, anionic and neutral, cannot be clearly distinguished by the methods usually applied in experiments (Mühr-Ebert et al, 2019). Moreover, Guillaumont et al (2003) remarked, that the constant of Bernhard et al (2001) is not precise since the analysis indicates large experimental errors.…”

“…They are based to a large extent on the use of chemical thermodynamic databases. Consequently, in addition to completeness, the selection of the data itself is also important as often various values dependend on the applied experimental conditions are given in literature (Thoenen et al, 2014;Mühr-Ebert et al, 2019). Because varying stability constants within the law of mass action change the overall aqueous species distribution and predominant species, the maximum migration distance of a radionuclide through a clay formation might be affected.…”