Kinetic studies of the dehydroxylation and crystallization of raw kaolinite and fluorides-modified kaolinite

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• 作者：Cornelia Păcurariu ; Ioan Lazău ; Radu Lazău
• 关键词：Kaolinite ; Dehydroxylation ; Crystallization ; Non ; isothermal kinetics ; Isoconversional methods
• 刊名：Journal of Thermal Analysis and Calorimetry
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：127
• 期：1
• 页码：239-246
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Physical Chemistry; Analytical Chemistry; Polymer Sciences; Inorganic Chemistry; Measurement Science and Instrumentation;
• 出版者：Springer Netherlands
• ISSN：1588-2926
• 卷排序：127

文摘

The effect of some fluoro compounds on the dehydroxylation and crystallization of kaolinite was investigated using thermal analysis. Samples were prepared starting from the raw kaolin (K-0) by adding 1 mass% fluorine, introduced as LiF (K-Li), NaF (K-Na) and CaF₂ (K-Ca), respectively. The results show that the peak temperatures of the dehydroxylation process are less influenced by the fluorides presence, whilst the peak temperatures of the crystallization process decrease in the presence of fluorides, which confirm the mineralizer effect of fluorides on the crystallization process. The activation energies of the dehydroxylation and crystallization processes were calculated using the isoconversional methods described by Kissinger–Akahira–Sunose and Vyazovkin. For the dehydroxylation process, the values of the activation energy calculated as a function of the conversion extent are not significantly influenced by the fluorides presence. For the crystallization process, all the samples with fluorides show values of the activation energy higher than those of the sample without fluorides on the entire range of the conversion extent.