Structural Environment of Uranium (VI) and Europium (III) Species Sorbed onto Phosphate Surfaces: XPS and Optical Spectroscopy Studies

• Published in: Journal of colloid and interface science Vol. 205; no. 2; pp. 410 - 416
• Main Authors: Drot, R., Simoni, E., Alnot, M., Ehrhardt, J.J.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15.09.1998; Elsevier
• Subjects: Chemical Physics; Chemistry; europium; Exact sciences and technology; General and physical chemistry; laser induced fluorescence; phosphate surfaces; Physics; Solid-liquid interface; sorption; Surface physical chemistry; uranium; XPS; XPS; uranium; phosphate surfaces; laser induced fluorescence; sorption; europium; Inorganic adsorbate; Liquid solid interface; Liquid solid adsorption; Adsorption site; Diphosphato complex; Uranium ion; Zirconium Complexes; Transition metal Complexes; Inorganic adsorbent; Experimental study; Fluorescence spectrometry; Oxo complex; Actinide Ions; Europium ion; Adsorption structure; Photoelectron spectrometry; Phosphato complex; Aqueous solution; Lanthanide Ions; scientific article; scientometric; journal
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.1998.5652

In order to characterize the structure of the surface complexes formed by interaction between uranyl and europium (III) ions and the surface of solid matrices, optical and X-ray photoelectron spectroscopies experiments on uranyl/europium loaded phosphate solids (Th4P2O7(PO4)4, ZrP2O7, and Zr2O(PO4)2) have been performed. The use of complimentary spectroscopic techniques allows an identification of the sorption mechanism and a structural characterization of the sorption sites and the sorbed species on phosphate surfaces. The samples were prepared from aqueous uranyl or europium solutions in the pH range from 1.5 to 6.0. The surface coverage was varied from 1 to 40 % of a monolayer. The differences between the emission spectra of europium ions either sorbed on the surface of phosphate samples or doped inside the solid unambiguously indicates that these sorbed ions are exclusively located on the surface and that they do not migrate inside the matrix, which shows clearly that surface complexation is involved during the sorption process. The U4fXPS spectrum of uranyl ions sorbed on zirconium diphosphate exhibits only one component, while the spectrum corresponding to uranium on thorium matrix shows two different unresolved peaks attributed to two different chemical environments. These results, corroborated by the uranyl emission spectra and the associated decay times and those obtained by optical spectroscopy of europium sorbed on the same solids, have been interpreted in terms of two sorption sites probably formed by the oxygens of the PO4and P2O7surface groups.