DETERMINATION OF SITE-SPECIFIC BINDING ENVIRONMENTS OF SURFACE SORBEDCESIUM ON CLAY-MINERALS BY CS-EXAFS

Transport behavior of Cs-137 in the environment is regulated by surfac e sorption reactions on clay mineral surfaces. To provide greater unde rstanding of Cs transport processes, XAFS investigations of the local environments of Cs-133 sorbed to clay minerals were conducted on Cs-Ca exchanged clay suspensions at the Cs Lm-edge. With decreased surface loadings of Cs, the Cs local environment exhibited increased long rang e order beyond 6 Angstrom. Identification of Cs in expanded, semi-coll apsed and collapsed interlayer environments was determined by correlat ing radial distances and Fourier transform peak amplitudes representin g Cs-O and Cs-Al/Si in the octahedral and tetrahedral layers. Despite the difficulties of analyzing XAFS data of adsorbed atoms in multiple environments, isolation of Cs in more specific sites by selective exch ange should allow detailed analysis and identification of predominant binding environments of cations to clay surfaces.