Local environment of iron and uranium ions in vitrified iron phosphate glasses studied by FeK and U L-III-edge x-ray absorption fine structure spectroscopy

The local structure of iron and uranium ions in a series of iron phosphate glasses with the general composition (40 - x)Fe2O3-xUO(2)-60P(2)O(5) and (1 -x-y) (40Fe(2)O(3)-60P(2)O(5))-xUO(2)-y(Na2O or CaO) was investigated using Fe K-edge and U L-III-edge x-ray absorption fine structure spectroscopy. R eplacing Fe2O3 by UO2 in the glass caused more distortion in the coordinati on environment of Fe(III) ions. Extended x-ray absorption fine structure fi ts revealed that the Fe-P bonds observed in the base glass also existed in all the waste-loaded glasses. X-ray absorption near-edge structure showed t hat the uranium ions were predominantly present as U(IV) in the glasses. Ur anium ions were coordinated to approximately 8 +/- 1 oxygen atoms and 2.5 /- 0.6 phosphorus atoms at an average distance of 2.47 +/- 0.02 and 3.8 +/- 0.02 Angstrom, respectively. There were no Fe-U or U-Fe neighbors observed , indicating that uranium ions occupied voids in the glass away from the PO 4 units. These conclusions were supported by Mossbauer, x-ray photoelectron , and Raman spectroscopic data.