X-RAY PHOTOELECTRON SPECTROSCOPIC STUDY OF COBALT(II) AND

Abstract--The safe disposal of 6 ~ 63Ni, and 59Ni has required considerable information on the inter-actions of Co 2+ and Ni 2+ with clay minerals in the geosphere. X-ray photoelectron spectroscopy (XPS) has been used to probe the sorption sites for Co 2+ and Ni 2+ on hectorite and montmorillonite. The spectra were measured for Co-hectorite, Ni-hectorite, and Ni-montmorillonite immediately following ion ex-change and after washing the clay two and five times with distilled water. The spectra, recorded following etching of the surface with an argon ion beam, differentiate wo sorption sites; a labile (to washing) fraction sorbed as ion pairs, and a non-labile fraction sorbed by ion exchange at broken bond and interlamellar sites. The data were consistent with the sorption of metal ions (Co 2 § NP +) in a common "MO6 " ligand environment. C & § had a greater affinity forexchange on hectorite than did NiZ+; but NP + had a greater affinity for the surface of montmorillonite than for hectorite. The argon ion etching of Ni-montmorillonite gave rise to a new photopeak of 853 eV, which was probably due to elemental Ni formed consequent tothe chemical violation of the surface by ion etching