Experimente zum Einfluß des Gesteinsglas-Chemismus auf die Zeolithbildung durch hydrothermale Umwandlung |
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Authors: | Ulrike Wirsching |
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Institution: | 1. Institut für Technische Petrographie und Mineralogie der Technischen Hochschule in Graz, ?sterreich
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Abstract: | In the formation of zeolites by hydrothermal alteration volcanic glasses are the starting material in most cases. The experiments aimed at demonstrating in what way the chemistry of the volcanic glass influences: - the alteration rate of the volcanic glass to zeolites,
- the kind of zeolites being formed and their formation conditions.
Three volcanic glasses were used, a basaltic, a phonolitic, and a rhyolitic one. The experimental conditions were as similar as possible to the natural alteration conditions. Solutions being used: H2O dist (pH ~5.5), 0.01 n NaOH (pH ~10.5), and solutions of similar chemistry to the natural ones. The temperatures were 180 °, 200 °, 250 ° C. The experiments were carried out both in closed and in open systems. The experimental results show a difference in the alteration rate and in the zeolites being formed between the basaltic and the phonolitic glasses on the one hand and the rhyolitic one on the other. In case of the closed system the SiO2-poor volcanic glasses react more rapidly than the SiO2-rich one. The zeolites being formed are chabazite, phillipsite, analcime respectively mordenite, analcime. In case of the open system the influence of the chemistry of the volcanic glass on the alteration rate and the zeolite being formed is less significant. Which zeolite is formed at a given temperature depends on: the chemistry of the starting material, the chemistry of the reacting solution and wether there is a closed or an open system. |
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