Speciation of Tracer Amount Metals at Solid-Liquid Interface by use of Quantum Beam

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There is an evidence that much of the radionuclides released into the geosphere exist as colloidal particles that may remain suspended, settle out of solution, and solidify with changes in condition. This report focuses on the adsorption of uranium (VI) on silver and gold colloidal particles. The chemical behavior of uranyl species in a nuclear waste repository is of considerable interest because in the case of direct disposal of the spent fuel, uranium is the main component and it governs the long-term release of radionuclides from spent fuel itself.We made measurements of Raman spectra of U (VI) ions loaded silver and gold colloidal particles for wide range of pH of the aqueous suspension. It was observed that Raman active symmetric stretching frequency of UO_2^<2+> ion shifts to smaller wavenumber when adsorbed onto silver colloidal particle, and that the shift depends on the pH of the suspension. This observation discounts the case that all U (VI) ligands are released following the adsorption onto silver colloidal particle.However, the Raman spectra did not extend pH dependency in the experiments of gold colloidal particles, thus the idea that all ligands are released following the adsorption was confirmed for U (VI) adsorption onto gold colloids.