An XPS Study of Interaction of Neptunyl(V) in Aqueous Solution with Goethite ( -FeOOH)

Sorption and physicochemical state of Np on the goethite (α-FeOOH) surface were studied. The oxidation state of Np on the α-FeOOH surface was studied by the liquid extraction. The neptunium complexes formed on the surface were studied by X-ray photoelectron spectroscopy. The ionic and elemental composition of the goethite surface and NpO 2 + complexes with α-FeOOH were determined from the XPS data. No Np(IV) and Np(VI) compounds were detected. Neptunyl(V) Np(V)O 2 + forms complexes with the surface groups of α-FeOOH. The equatorial plane of these complexes is occupied by the oxygen atoms of α-FeOOH and water and/or carbonate group CO 3 2− .