Abstract
Experiments were conducted to evaluate the effects of aging and temperature on surface speciation of cadmium (Cd) and lead (Pb) on kaolinite using X-ray absorption fine structure (XAFS) spectroscopy and column desorption experiments. Cd formed outer-sphere complexes on kaolinite and there were no detectable changes in XAFS fitting results due to aging and temperature. A decrease in Cd desorption after 60 days at 40°C was observed along with small changes in the XAFS for this sample between 10 and 11 Å-1, which could not be quantified using non-linear fitting. A significant decrease in Pb desorption from kaolinite was due to the formation of polynuclear Pb-hydroxide complexes, which with increased aging stabilized at the kaolinite surface. Increased stability coincided with greater Pb-Pb edge sharing, suggesting an increase in size of polynuclear complexes with age and temperature. The Pb desorption behavior showed that time was a more effective stabilizing factor than temperature, suggesting that polynuclear Pb complexes may undergo Ostwald ripening.
| Original language | English |
|---|---|
| Title of host publication | Adsorption of Metals by Geomedia II |
| Subtitle of host publication | Variables, Mechanisms, and Model Applications |
| Editors | Mark Barnett, Douglas Kent |
| Pages | 205-233 |
| Number of pages | 29 |
| DOIs | |
| State | Published - 2007 |
Publication series
| Name | Developments in Earth and Environmental Sciences |
|---|---|
| Volume | 7 |
| ISSN (Print) | 1571-9197 |
Funding
We gratefully acknowledge the financial support of the Australian Synchrotron Research Program. We thank Garry Foran at the Australian National Beamline Facility (20B) at the Photon Factory of the National Laboratory for High Energy Physics (KEK), Tsukuba, Japan, for his assistance and facility support for the Pb EXAFS experiments. We also thank Steve Heald for his help in conducting the Cd EXAFS experiments at the PNC-CAT beamline 20BM at the Advanced Photon Source, Argonne, IL, USA. PNC/XOR facilities at the Advanced Photon Source, and research at these facilities, are supported by the US Department of Energy – Basic Energy Sciences, a major facilities access grant from NSERC, the University of Washington, Simon Fraser University, the Pacific Northwest National Laboratory and the Advanced Photon Source. Use of the Advanced Photon Source is also supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-Eng-38. We would like to thank Navdeep Kaur for her assistance in EXAFS sample preparation. We also acknowledge the critical suggestions by Douglas Kent and three anonymous reviewers to improve the manuscript.