Infrared and Raman spectra of uranyl(VI) oxo-hydroxo complexes in acid aqueous solutions: a chemometric study

IR-ATR and Raman spectroscopies are used to identify the complexed species of uranyl with hydroxide in aqueous solutions as a function of pH in the ra nge 1.55-4.20. For [U-tot] = 0.1 M and an ionic strength between 0.23 and 0 .35 M, three species are observed via irregular shifts of the uranyl stretc hing signals: UO2(H2O)(5)(2+), (UO2)(2)(OH)(2)(H2O)(6)(2+) and (UO2)(3)O(OH )(3)(H2O)(6)(+). No evidence of the presence of compound (UO2)(2)(OH)(H2O)( 8)(3+) was shown in these conditions. A chemometric approach using the mult ivariate method PLS2 is used to confirm the absence of(UO2)(2)(OH)(H2O)(8)( 3+) and to extract the single spectra of the species in solution. (C) 2000 Elsevier Science B.V. All rights reserved.