{sup 133}Cs NMR study of cesium on the surfaces of kaolinite and illite
- Univ. of Illinois, Urbana, IL (United States)
- Sandia National Lab., Albuquerque, NM (United States)
{sup 133}Cs MAS NMR of Cs-exchanged illite, kaolinite, boehmite, and silica gel is shown to be a powerful tool to investigate the adsorption sites and atomic dynamics of Cs on mineral surfaces. Cesium is adsorbed on these mineral surfaces in primarily two ways: at sites relatively tightly bonded to the surface (Stern layer, Cs1) and at more loosely bonded sites in the diffuse (Gouy) layer (Cs2). For illite, both edge sites and crystallite basal surfaces are important adsorption sites. For kaolinite, edge sites, expandable layers, and probably crystallite basal surfaces are important. The {sup 133}Cs NMR chemical shifts of Cs2 do not vary systematically with solid composition due to the larger distance sites from the surface and weaker electrostatic attraction to the surface compared to Cs1. Rather, the Cs2 chemical shifts are significantly influenced by relative humidity (R.H.) and Cs population (Cs/H{sub 2}O ratio) on the surface. The Cs1 chemical shifts vary less with these parameters. Cs2 is removed by washing with 1-5 mL of deionized water due to its weak attraction to the surface. The Cs1 chemical shifts become less shielded after washing and with decreasing solution concentration due to a decrease in the Cs surface density. At 100% R.H., Cs in the two sites undergoes motional averaging at frequencies > 100 kHz. With decreasing R.H., peaks for Cs on the two sites are resolved due to decreasing exchange frequencies related to a decreasing number of adsorbed water layers. Motional averaging at 100% R.H. is verified by low temperature experiments with illite. 69 refs., 9 figs., 2 tabs.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 508600
- Journal Information:
- Geochimica et Cosmochimica Acta, Vol. 60, Issue 21; Other Information: PBD: Nov 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
The structural environments of cations adsorbed onto clays: A sup 133 CsMAS NMR spectroscopic study
The sorption behavior of Cs and Cd onto oxide and clay surfaces