ADSORPTION ENERGY EVALUATION FROM LUMINESCENT MEASUREMENTS OF URANYL IONS $(UO^{2+}_{2})$ ADSORBED ON DISPERSE SILICA SURFACES

$^{a}$Yu. D. Glinka, T B. Krak, Phys. Rev. B 52, 14985 (1995).Author Institution: Separation and Surface Science Center, Department of Chemistry, Kent State University; Institute of Surface Chemistry of the National, Academy of Sciences of UkraineLuminescent measurements were utilized to evaluate the adsorption energy for hydrated uranyl groups on the disperse silica surface. The position of The $UO_{2}^{2+}$ 0-0-electronic transition and frequencies of intramolecular vibrations of luminescence spectra related to the adsorption of hydrated uranyl groups on different types of surface active sees were used in that $evaluation^{a}$, which was based on the dependence of the adsorption bond force constants corresponding to each type of surface sites on the respective perturbation $energy^{1}$ of uranyl ions. The molecular adsorbate on the silica surface was modeled by means of hypothetical diatomic and triatomic molecules with $C_{\infty V}$ and $C_{2v}$ symmetry, in which the $UO_{2}^{2+}$ ion was predominantly fixed on the silica surface through one and two water molecules, respectively. The perturbations of stretching and deformational vibrations of hypothetical molecules by the presence of the substrate were considered. It was shown that due to a large value of uranium mass the proposed models can be used for the analysis of vibrational spectra of hydrated uranyl groups adsorbed on the silica surface. Adsorption energies for different types of active Sites on the silica surface wore evaluated for physical and chemical adsorption