Determination of Site Specific Binding Environments of Surface Sorbed Cesium on Clay Minerals by Cs-EXAFS

Transport behavior of '37Cs in the environment is regulated by surface sorption reactions on clay mineral surfaces. To provide greater understanding of Cs transport processes, XAFS investigations of the local environments of 133Cs sorbed to clay minerals were conducted on Cs-Ca exchanged clay suspensions at the Cs LIII-edge. With decreased surface loadings of Cs, the Cs local environment exhibited increased long range order beyond 6 A. Identification of Cs in expanded, semi-collapsed and collapsed interlayer environments was determined by correlating radial distances and Fourier transform peak amplitudes representing Cs-0 and Cs-AVSi 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 exchange should allow detailed analysis and identification of predominant binding environments of cations to clay surfaces.