A 25% niobium substituted sitinakite was exchanged with strontium as time resolved X-ray diffraction data was collected. The structural modeling of this data by Rietveld method1 has lead to the determination of the atomic positions of the ions and unit cell parameters as strontium occupancy increases.
The starting material of the exchange experiment is the protonated phase, H2Nb0.67Ti1.33SiO7·1.9 H2O, with space group P42/mcm2,3. Once strontium (Sr2+) enters the unit cell, extra-framework H2O molecules shift to provide the necessary hydration coordination. These new positions of H2O result in a lowering of symmetry to the P-42m space group, and it is thought that the new hydrogen bonding network serves to enhance strontium ion diffusion into the channels of sitinakite. Exchange of strontium into the microporous material reaches a maximum fractional occupancy of 21% when a 10.0 mM strontium ion solution is forced over the powdered material. Sequestration of strontium into this material has contributed valuable information to the study of microporous materials and ion exchange chemistries.
| Identifer | oai:union.ndltd.org:WKU/oai:digitalcommons.wku.edu:theses-2072 |
| Date | 01 May 2011 |
| Creators | Kramer, Samantha Jane |
| Publisher | TopSCHOLAR® |
| Source Sets | Western Kentucky University Theses |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses & Specialist Projects |
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