Interaction of Neptunyl with Goethite (alpha-FeOOH), Maghemite (gamma-Fe_2O_3), and Hematite (alpha-Fe_2O_3) in Water as Probed by X-ray Photoelectron Spectroscopy

摘要

The sorption behavior is studied and the physicochemical neptunium species existing on the surface of goethite (alpha-FeOOH), maghemite (gamma-Fe_2O_3), and hematite (alpha-Fe_2O_3) are determined. Solvent extraction and X-ray photoelectron spectroscopy (XPS) are used to determine the neptunium surface species. The ion and elemental composition of the surface of the minerals and surface neptunyl NpO_2 complexes is determined using these data. Compounds containing neptunium(IV) or neptunium(VI) ions do not appear; rather, neptunyl (Np(V)O_2 group is complexed with surface hydroxide groups of alpha-FeOOH, gamma-Fe_2O_3, and alpha-Fe_2O_3. Presumably, the oxygen atoms of iron oxides and water and/or carbonate (CO_3~(2-)) or nitrate (NO_3~-) group lie in the equatorial plane of the neptunyl (NpO_2~+) group.