Treatment of radioactive wastes: an X-ray absorption spectroscopy study of the reaction of technetium with green rust.

摘要: Technetium is a long-lived product of nuclear fission that readily forms the soluble pertechnetate anion [TcO4]−. Green rusts (layered hydrous oxides containing both Fe(II) and Fe(III) with interlayer sulfate or carbonate anions) concentrate >99.8% 99Tc, present as [TcO4]−, from aqueous solution, even in presence high concentrations NaNO3, common constituent radioactive waste streams. The mechanism removal solution apparently reduction formation strong Tc(IV) surface complexes. X-ray absorption spectroscopy shows [TcO4]− indeed reduced by reaction sulfate- carbonate-form green found TcO2-like environment. On contact air, oxidize to poorly crystalline goethite but Tc environment unchanged. There no increase solubility associated oxidation host rust. This behavior suggests may be useful treatment Tc-containing streams, groundwater cleanup, restricting migration repositories.