Ce L-III-edge X-ray absorption spectroscopic studies on the tetrameric Ce-polyoxyhydroxy cation intercalated aluminosilicate

The cerium ion intercalated aluminosilicate was prepared by ion exchange re action between Na+ in montmorillonite and Ce4+ in aqueous solution. The X-r ay absorption near edge structure (XANES) analyses indicate that the Ce4+ i ons are partially reduced to the Ce3+ ones during the intercalation into la yered aluminosilicate due to a charge transfer between host and intercalant . From the EXAFS analysis, two different (Ce-O) bonding pairs could be char acterized with the distances and coordination numbers of 2.31 (+/-0.02) Ang strom x 8.2 (+/-1.5) and 2.66 (+/-0.02) Angstrom x 2.7 (+/-1.0), respective ly, with the oxygen atoms as the first nearest neighbor, and two (Ce-Ce) pa irs at 3.78 Angstrom as the second neighbor. It is therefore concluded that the most probable Ce-species stabilized in the interlayer space of alumino silicate after the intercalation is the tetrameric Ce-polyoxy/hydorxy catio ns with the mixed valent state of 0.75 Ce4+/0.25 Ce3+.