Кінетичні параметри процесу відновлення гематиту до магнетиту за допомогою біомаси
| Autor: | V. P. Ponomar, A. B. Brik, N.O. Dudchenko |
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| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | Вісник Дніпропетровського університету. Геологія, географія. 25:53-62 |
| ISSN: | 2409-9864 2313-2159 |
| DOI: | 10.15421/111707 |
| Popis: | Kinetics of hematite to magnetite reduction by starch at relatively low temperatures (300–600 °С) during the time interval of 5–30 min has been investigated using the method of thermomagnetic analysis. The transformation process was accompanied by permanent measurement of magnetization of the sample. The rate of sample heating/cooling was 65°/min. It was shown that the starting temperature of the reaction was approximately 350 °C. Curie temperature of transformed samples was 555 °С corresponding to the Curie temperature of bulk pure magnetite (580 °C). According to the X-Ray diffraction data, the initial sample consisted of hematite. This sample, annealed at 400 °С, did not demonstrate magnetite reflexes; nonetheless, the magnetization of this sample increased considerably, suggesting the magnetite formation in the sample. This disagreement can be explained by a higher sensitivity of thermomagnetic analysis in comparison to X-Ray diffraction method. The samples, annealed at 500 and 600 °С, showed magnetite reflexes in addition to hematite reflexes. The raise of annealing time increased saturation magnetization of the transformed samples. The sharp increase in magnetization during the initial 5 minutes of reduction was observed for the samples annealed at 500 and 600 °C. Only a small increase in magnetization was observed for the time interval of 10–30 min for all temperatures. Saturation magnetization of transformed samples increased tenfold up to 35 А·m2/kg for the samples acquired at 600 °С. The kinetics parameters of the process were calculated using the obtained data of saturation magnetization. Two stages of the reduction reaction were determined: the first stage is the fast formation and the growth of magnetite nuclei on the surface of hematite; and second stage is the reaction interface progress towards the core of the hematite grain. The rate constants for each temperature and activation energy equal to 32 kJ/mol were calculated for the second stage of the reaction. Obtained data are essential for solving applied and theoretical problems of modern mineralogy. |
| Databáze: | OpenAIRE |
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