The change in the Raman band of uranyl, UO22+, at about 870 cm-1 due to the formation of complexes with various ligands is proven to be very informative for investigating the complexation of uranyl. The linear uranyl cation unit, O=U=O, gives a strong and sharp Raman band in the range of 700-900 cm-1 originated from the symmetric stretch vibration (ν1) while exposed to a laser beam. The symmetric stretch vibration (ν1) of uranyl is apparently affected by the association between uranyl and the coordination ligands in the equatorial plane, and the exact change in ν1 depends on the ligands attached. By using Raman spectrometry, the complexation of uranyl ion in solutions, containing very weak/non-coordinating NO3- or ClO4- as internal standard, with weak ligands (carboxylate), with moderate ligand (C2O42-), and with very strong ligands (dipicolinic acid, DPA and fluoride) has been investigated with spectral titration method. The results suggest that the linear relationships between the concentrations of the species and the corresponding Raman band intensities can be utilized to determine their concentrations, and further to study the complexation of uranyl with various ligands.

Investigation on complexation of uranyl with Raman spectroscopy: Coordination mode, intensity, and related Raman shift

2019 Spring National Meeting

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