Water determination in iron oxyhydroxides and iron ores by Karl Fischer titration
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- 作者：Camila C. R. F. da Cunha ; Geraldo M. da Costa
- 关键词：Water content ; Hydrohematite ; Protohematite ; Hematite
- 刊名：Physics and Chemistry of Minerals
- 出版年：2016
- 出版时间：November 2016
- 年：2016
- 卷：43
- 期：10
- 页码：739-748
- 全文大小：781 KB
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth sciences
Mineralogy
Crystallography
Geochemistry
Mineral Resources - 出版者：Springer Berlin / Heidelberg
- ISSN：1432-2021
- 卷排序：43
文摘
Protohematite (Fe2−x/3(OH)xO3−x 1 ≤ x < 0.5) and hydrohematite (Fe2−x/3(OH)xO3−x 0.5 ≤ x < 0) are iron-defective phases containing hydroxyl groups in their structures. These species were described in prior studies mainly with the aid of X-ray diffraction and Infrared spectroscopy. The existence of these phases in soils might have influence in redox processes, and they were considered as a possible water reservoir in Martian soils. In this study, we have used for the first time the Karl Fischer titration method to determine the amount of water released after heating several synthetic samples of goethite, hematite and natural iron ores at 105, 400, 600 and 900 °C. It was found that heating at 105 °C did not remove all moisture from the samples, and higher temperatures were necessary to completely remove all the absorbed water. The water contents determined at 400, 600 and 900 °C were found to be the same within the experimental errors, suggesting the inexistence of both protohematite and hydrohematite in the investigated samples. Therefore, the above-mentioned effects of these phases in soils might have to be reevaluated.