Hydrolysis of Uranyl(VI) in Acidic and Basic Aqueous Solutions Using a Noncomplexing Organic Base: A Multivariate Spectroscopic and Statistical Study

In the field of actinide aqueous chemistry, this work aims to resolve some controversy about uranyl(VI) hydroxide species present in basic aqueous solutions. We revisit the Raman, IR, and UV−visible spectra with two new approaches. First, Raman, IR and UV data were recorded systematically from aqueous solutions with the noncomplexing electrolyte (C2H5)4NNO3 at 25 °C and 0.1 MPa ([Utotal] = 0.005−0.105 M) in H2O and D2O over a wide range of −log mH(D)+ between 2.92 and 14.50. Second, vibrational spectra (IR and Raman) of basic solutions in H2O and D2O were analyzed using the Bayesian Positive Source Separation method to estimate pure spectra of individual species. In D2O solutions, the new spectroscopic data showed the occurrence of the same species as those in H2O. As observed for the wavenumber of the symmetric stretching mode, the wavenumber characteristic of the O═U═O antisymmetric stretching mode decreases as the number of OH(D)− ligands increases. These kinds of data, completed by (1) analysis of the...