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Study of the thermal stability of the natural zeolite heulandite

F. Pechar and D. Rykl

Institute of Geology and Geotechnics, Czechoslovak Academy of Sciences, CS-182 09 Prague


Abstract: On the basis of the course of the DTA and TGA curves the natural zeolite heulandite (Poonah locality, India) was subjected to the isothermal decomposi­ tion at the various temperatures (0/°C: 20, 200, 280, 470, 510, 620, 660, 760, 820, and 1000). The decomposition products were studied by means of the X-ray powder methods and by the infrared absorption spectroscopy. It was found that the heulandite structure is stable up to the temperature of 280 °C. At the temperature exceeding 280 °C the transformation into the modification of heulandite В occurs. From the temperature of 47.0 °C upwards the amor­ phous phase begins to be formed, from which at the temperature exceeding 500 °C a mixture of minerals wairakite 4- a-Si0 2 and/or anorthite + Si0 2 starts to appear. In the course of dehydration starting from 200 °C, in the cavities of heulandite simultaneously proceeds the heterolytic reaction, at which the free proton is formed, which immediately attacks the bridge oxygens in the bridge ( ) — Al—О—Si under the formation of hydroxyl groups. These groups partly remain in the complicated complex up to the high temperatures.

Full paper in Portable Document Format: 393a369.pdf


Chemical Papers 39 (3) 369–377 (1985)

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