Effects of cation and sorption site type on metal ion sorption on clay minerals: An x-ray absorption spectroscopic study
- Desert Research Institute, Las Vegas, NV (United States)
- Univ. of Michigan, Ann Arbor, MI (United States)
Metals dissolved in natural aquatic environments are often sorbed on high surface area, clay minerals. The relative importance of these minerals for cation retardation is a function of cation type, adsorbent characteristics, and other geochemical conditions, such as pH and ionic strength. A parametric X-ray Absorption Spectroscopic (XAS) study of Co(II) sorption on montmorillonite (pretreated for carbonate, iron oxide, and organic matter removal) suggests that the Co coordination environment depends on solution conditions. At low pH and Na ion concentration Co(II) forms outer-sphere, mononuclear surface complexes with permanent-charge sites in the interlayer region of smectites. At high pH or Na ion concentration Co(II) is excluded from the interlayer permanent-charge sites and forms polynuclear species or a surface precipitate on external surface-hydroxyl sites. Analysis of XAS data from Sr sorption complexes on kaolinite and montmorillonite is consistent with formation of mononuclear outer-sphere complexes regardless of substrate and solution conditions. These studies confirm that the effect of changing solution conditions on cation mobility depends both on metal ion type and clay mineral sorbent.
- OSTI ID:
- 370495
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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