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Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/194014
Thermal behaviour of kaolinitic raw materials from San José (Oruro, Bolivia)
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Kaolin is widespread as a result of the alteration in the San José Sn-Ag deposit located in Oruro, Bolivia. This study presents a chemical, mineralogical and thermal characterization of the San José kaolinitic deposit, which is necessary to determine their optimal applications. Mineral phases of these white silty kaolinitic materials were determined by X-ray diffraction (XRD) and are quartz, kaolinite, K-feldspar, muscovite, illite and minor halloysite, dickite, plagioclase, jarosite, rutile, alunite and gypsum. The fraction < 63 µm contains 20-27 mass% of kaolinite. Differential thermal analysis (DTA) shows an endothermic peak at 520 °C associated with the dehydroxylation of kaolinite and an exothermic peak at ~ 980 °C related to the crystallization of mullite. TG curves show a total mass loss up to 1300 °C of about 8 mass%. The dilatometric curves show a shrinkage at about 890 °C produced by the collapse of metakaolinite into a spinel-like structure, and another shrinkage starts at 1010 °C, at the beginning of the sintering, when the spinel-like phase is transformed to mullite and amorphous SiO2. Lightness L* is 80-92, but only the mined materials have b* < 4, suitable for paper filling applications.
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ALFONSO ABELLA, María Pura, et al. Thermal behaviour of kaolinitic raw materials from San José (Oruro, Bolivia). Journal of Thermal Analysis and Calorimetry. 2022. Vol. 147, num. 9, pags. 5413-5421. ISSN 1388-6150. [consulted: 14 of June of 2026]. Available at: https://hdl.handle.net/2445/194014