Direct spectroscopic speciation of schoepite-aqueous phase equilibria

UV-Vis spectra of solutions in solid-aqueous phase equilibrium with UO3 x 2H2O(s) and 0.03 kPa CO2 partial pressure are quantitatively analyzed by single component spectra of hydrolysis species UO22+(aq), (UO2)2(OH)22+ and (UO2)3(OH)5+. From the deconvoluted spectra, single species concentrations are obtained and interpreted by various statistical methods. Relationship of UV-Vis data to fluorescence spectroscopic analysis of the same system is discussed. Calculation of thermodynamic quantities gave consistent results, both within experimental data and with results from solubility studies and spectroscopic analysis from literature. A reinterpretation of some literature data is proposed. (author)