Details

Autor(en) / Beteiligte

• Wang, Xinyu
• Shi, Zeming
• Kinniburgh, David G.
• Zhao, Laishi
• Ni, Shijun
• Wang, Ruilin
• Hou, Yun
• Cheng, Ke
• Zhu, Bocheng

Titel

Effect of thermodynamic database selection on the estimated aqueous uranium speciation

Ist Teil von

• Journal of geochemical exploration, 2019-09, Vol.204, p.33-42

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2019

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• A complete and accurate set of thermodynamic data for aqueous uranium species is necessary in order to determine the toxicity of uranium in water, to predict its fate in the environment and to design possible remediation strategies for polluted environments. Comparisons of the completeness and accuracy of the thermodynamic databases for aqueous uranyl complexes involving common inorganic anions (OH−, SO42−, PO43−, CO32−, SO42−, Cl−,F−, I−, Br−) and some organic ligands have been made between a number of publicly-available thermodynamic databases (MINTEQ, LLNL, WATEQ4F, ThermoChimie, NEA-TDB, and PSI/Nagra). The results indicates that: (1) stability constants for most aqueous inorganic uranium species in the ThermoChimie, NEA-TDB, and PSI/Nagra databases are broadly similar, but ThermoChimie includes a greater number of organic uranium species; (2) ThermoChimie and two other modern developing databases (NEA-TDB, and PSI/Nagra) are recommended for calculating uranium speciation in natural/polluted waters except for those containing high concentrations of inorganic phosphate; (3) the stability constant for U(OH)4 from the LLNL database is much greater than the values found in the other databases (by four orders of magnitude) and needs to be replaced; (4) the MINTEQ, LLNL, and WATEQ4F databases need updating for many important uranium species including Ca2UO2(CO3)3, UO2(H2AsO4)2 and all the organic uranium species, and (5) the MINTEQ database does not include U(IV)‑bromine, U(IV)‑iodine or U(IV)-nitrate complexes, while the other databases do not include U(IV)-phosphate complexes. A case study of the water chemistry in a phosphate mining region of China, including river water from close to a fertilizer plant, indicates that the calculated uranium speciation varies greatly between the different databases. In particular, the existence and stability of the UO2(HPO4)22− species needs confirmation and quantification including supporting spectroscopic measurements. Although the stability of the stronger bioavailable uranyl-phosphate complexes remains uncertain, the available thermodynamic data suggests that the proportion and toxicity of most uranyl-phosphate complexes will be negligible when the pH exceeds 8.5 and the inorganic phosphate concentration (as PO43−) is <2 mg/L. •Stability constants of aqueous uranium species of six thermodynamic databases available were investigated and compared.•ThermoChimie and two other databases are recommended for most waters except those with high inorganic phosphate.•Most uranyl phosphate complexes are negligible when pH exceeds 8.5 for water with phosphate (as PO43–) is ≤ 2 mg/l.