G°, H°,S°, K).| Year of Award: | 1996 |
| Amount of Award: | $599,999 |
| Problem Areas: | High Level Waste (primary) Mixed Waste Remedial Action |
| Science Category/SubCategory: | Separations Chemistry / Ligand Design and Ion-exchange |
| Lead Principal Investigator: | Dr. Abraham Clearfield Texas A&M University P.O. Box 300012 College Station, Texas 77842-3012 409-845-2936, pjf2434@acxrd.chem.tamu.edu |
| Principal Investigator at Oak Ridge National Laboratory: | Jack L. Collins Oak Ridge National Laboratory P.O. Box 2008 Oak Ridge, Tennessee 37831 423-574-6689, collinsjl@ornl.gov |
| For More Information: | |
| Other EMSP Research: |
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Description Provided by Investigator:
This research is concerned with the development of highly selective inorganic ion exchangers for the removal of primarily Cs+ and Sr2+ from nuclear tank waste and from groundwater. In this study, we will probe the, origins of selectivity through detailed structural studies and the thermodynamics of the ion exchange processes. The compounds to be synthesized may have cavity or tunnel structures, layer structures, or be amorphous gels. In our previous work, we have prepared highly selective Cs+ and Sr2+ sorbents, including a new family of alkali metal group 4(14) polysilicates. The structures of one of the polysilicates and titanium silicates with tunnel structures have been solved by ab initio powder methods and refined by Rietveld techniques. We have then probed the ion exchange process by preparing the protonated form of the exchanger and refined the structure at different levels of ion uptake. At the same time, NMR spectra of 29Si were obtained. These studies revealed the intimate details of the ion exchange process and similar procedures will be applied to the crystalline exchangers exhibiting high selectivities. It has been observed that the selectivities, particularly of the exchangers with tunnel structures, can be significantly altered by framework substitution and by the degree of crystallinity built into the exchangers. Therefore, systematic substitutions of framework ions based on ionic radii and charge will be carried out, and their effect on selectivity determined. Crystallinity will be controlled by the time, temperature, and pressure of synthesis. These studies will be used to predict the thermodynamics of exchange and tested by carrying out measurements of their thermodynamic properties (G°, H°,S°, K).
The starting point of our research is conditioned by our previous studies in which highly selective exchangers for Cs+ and Sr2+ have already been prepared, including the polysilicates, pharmacosiderites, and other silicates with tunnel structures, micas, and brittle micas for immobilization of ions in soils, layered titanates as strontium sorbers, and pillared clays and titanates. In addition, over a 30 year period we have synthesized many families of exchangers that can be applied to specific problems involving Pb2+ , Cd2+, Hg2+, Co2+, etc. contamination. In order to be aware of these problems and to be able to apply our studies to real waste problems, we propose a collaboration with Oak Ridge National Laboratory personnel who are engaged in actual waste cleanup problems. They are experts in producing inorganic exchangers in usable engineered forms and in column studies.
The full list of Environmental Management projects that could potentially be addressed by awards such as this one, which deals with High Level Waste, Mixed Waste, and Remedial Action problems, are listed in the Index of High Cost Environmental Management Projects by Problem Area, in the back of this appendix, under the headings "High Level Waste, Mixed Waste, and Remedial Action".
The following projects were identified through systems engineering as potentially having needs that can be addressed through this research award. Those projects that may have the strongest link to this award are designated by the symbol "§".