A New View Of Ion Adsorption At Mineral-Fluid Interfaces with X-ray Standing Waves

P. Fenter

Argonne National Laboratory

Knowledge of ion adsorption behavior at mineral-water interfaces is fundamental to understand the mobility of elements in the environment, but relatively little is directly known about the structures and distributions of ions at mineral-water interfaces. Here I discuss our recent efforts to determine the distribution of Sr2+, Zn2+, and Y3+ ions near the rutile(110)-water interface. The surface charge evolution of rutile (TiO2) surfaces is typical of oxide surfaces and is determined by surface protonation reactions. I describe how X-ray standing waves (XSW) is a powerful method to determine ion distributions at mineral-water interfaces. Here I describe both traditional approaches to determining ion adsorption sites (e.g. XSW triangulation) and recent efforts whereby ion distributions are directly revealed through a model-independent approach. These results reveal substantial (and some unexpected) differences in the ion adsorption geometries for Sr2+, Zn2+ and Y3+ ions.

This work is done in collaboration with Z. Zhang, L. Cheng, C. Park, D. J. Wesolowski, M. Machesky, M. J. Bedzyk, and N. C. Sturchio

Back to SSRL Users' Meeting Program