Thermodynamic and structural aspects of the aqueous uranium(iv) system – hydrolysis vs. sulfate complexation. Issue 48 (29th November 2019)

• Record Type: Journal Article
• Authors: Lehmann, Susanne; Foerstendorf, Harald; Zimmermann, Thomas; Patzschke, Michael; Bok, Frank; Brendler, Vinzenz; Stumpf, Thorsten; Steudtner, Robin
• Is Part Of: Dalton transactions. Volume 48:Issue 48(2019)
• Page Start: 17898
• Page End: 17907
• Publication Date: 2019-11-29
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9dt02886b
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The aquatic speciation of U(iv ) in acidic sulfate solution were studied by optical spectroscopy, quantum-chemical calculations, and thermodynamic modelling. Abstract : The aquatic species of U(iv ) in acidic aqueous solution in the presence of sulfate were studied in the micromolar range by a combined approach of optical spectroscopy (UV/vis and mid-IR), quantum-chemical calculations (QCC), and thermodynamic modelling. The number of species occurring in solution within the pH range 0–2 was assessed by decomposition and fitting of photometric spectra using HypSpec and Geochemist's Workbench software. Single component spectra of U 4+, UOH 3+, USO4 2+ and U(SO4 )2 were obtained and extinction coefficients ε λ were calculated to be 61.7, 19.2, 47.6 and 40.3 L mol −1 cm −1, respectively. Complex formation constants of two U(iv ) sulfate species and the first hydrolysis species UOH 3+ in infinitely diluted solution were determined by thermodynamic modelling to be log β θ 101 = 6.9 ± 0.3, log β θ 102 = 11.8 ± 0.5 and log β θ 110 = −(0.36 ± 0.1), respectively. No further U(iv ) sulfate and hydrolysis species were observed under the prevailing conditions. Molecular structural information of the sulfate species was derived from vibrational spectra and QCC exhibiting a predominant monodentate coordination of the sulfate ions.