Chemistry and mineralogy of iron-substituted kaolinite in natural and synthetic systems /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1981.
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| Subjects: | |
| Online Access: | Link to ProQuest copy Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | Seven soil kaolinites and four geologic kaolinites were studied to determine the extent, valence, and coordination number of iron in the kaolinite structure. Three synthetic kaolinites of varying iron content, as well as one synthetic smectite, were also studied ad compared with the natural samples. Selective dissolution techniques, using boiling alkali, revealed that anatase and mica were the major contaminating phases present in the natural samples. After boiling the samples in 6 N HCl, there was no indication that iron, oxides, possibly even as an occluded form were remaining in the kaolinite samples. Three spectroscopic techniques, electron spin resonance spectroscopy, Mössbauer spectroscopy, and infrared spectroscopy revealed that Fe^3+ is present only in octahedral coordination in the natural kaolinites. Charge density data and elemental analysis complemented the spectroscopic data. The synthetic sample contain Fe^2+ and Fe^3+ in their structure; presumably both ion are in octahedral coordination. Though the coordination is octahedral, the symmetry of the iron is distorted to orthorhombic in all samples. This distortion probably is due both to the presence of two different anions coordinating the Fe^3+ (O^2- and OH^-), and to the physical distortion of the filled octahedra in dioctahedral mineral. The fact that Fe^3+ is present in octahedral coordination is thermodynamically logical because there would be no charge imbalance and because the size of the Fe^3+ ion is similar to Al^3+ than to Si^4+. In the synthetic samples there is some evidence to suggest that at least some of the Fe^2+ ions are present in trioctahedral "cells" within the dioctahedral mineral. This would maintain charge balance. Since there is no charge deficit created by octahedral substitution of Fe^3+, there is no obvious formation of permanent charge. However, there does seem to be a correlation between increasing iron content and decreasing crystallinity and particle thickness in the natural samples... |
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| Item Description: | "Major subject: Soil Science." Typescript (photocopy). Vita. |
| Physical Description: | xiv, 224 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 204-216). |