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EN
Mexico has important kaolin deposits, which must be assessed to obtain products with a high commercial value, such as kaliophilite as raw material for biodiesel production. Two kaolins, A and B, with approximate SiO2:Al2O3 ratios of 1 and 1.2, respectively, were used as raw materials to produce kaliophilite. Both kaolins were obtained from the municipality of Agua Blanca in the State of Hidalgo, Mexico. Kaolins are a source of Al and Si for the synthesis of kaliophilite through an alkali fusion process at 700 °C followed by ultrasonic treatment at 28 kHz to different times and for Kaolin-KOH ratios of 1:1 and 1:1.2 (mass: mass). The kaolins as received and the alkaline mixtures heat and ultrasonically treated were analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). The most suitable kaolin for synthesizing kaliophilite was kaolin A with the Si/Al mass ratio of approximately 1, which exhibited a higher crystallinity index range from 54 to 79.6%. Higher KOH concentrations promote the amorphous material formation decreasing the kaliophilite amount. The crystallinity index was increased when the time of ultrasonic treatment was increased.
EN
The mineralogy and thermal properties of two kaolin clay samples from Agua Blanca (Hidalgo-México) were determined by XRD, SEM-EDS, TGA-DSC techniques. Kaolin clay A contains a higher Al2O3 and lower impurities (K2O, TiO2, Fe2O3) amount than kaolin clay B, while the SiO2 amount is similar for both kaolin clays. A theoretical approach was carried out by a thermodynamic analysis considering the chemical composition of both kaolin clay samples with the FactSage 7.3 software. Stability phase diagrams were obtained to different K2O content from 0.1 to 3 wt % and temperatures in the range from 600 to 1600°C based on the chemical composition of the kaolin clay samples. The main mineralogical compounds predicted are andalusite (Al2O3•SiO2), K-Potash feldspar (K2O•Al2O3•6SiO2), and the SiO2 polymorphs (quartz, tridymite, and cristobalite) with small amounts of ferric-pseudobrookite (Fe2O5Ti), and rutile (TiO2). As K2O content is increased, the amounts of mullite and tridymite decrease meanwhile the potash feldspar is increased at high temperatures. A liquid phase is formed at around 1350 and 1400°C for the kaolin clay samples A and B, respectively. The viscosity of the melt is increased for the evaluated K2O additions to 1400, 1500, and 1600°C.
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