Thermal decomposition of hydrotalcite with chromate, molybdate or sulphate in the interlayer

The thermal decomposition of hydrotalcites with chromate, molybdate and sulphate in the interlayer has been studied using thermogravimetric analysis coupled to a mass spectrometer measuring the gas evolution. X-ray diffraction shows the hydrotalcites have a d(0 0 3) spacing of 7.98 Å with very small...

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Bibliographic Details
Published in:Thermochimica acta 2005-05, Vol.429 (2), p.179-187
Main Authors: Frost, Ray L., Musumeci, Anthony W., Bostrom, Thor, Adebajo, Moses O., Weier, Matt L., Martens, Wayde
Format: Article
Language:English
Subjects:
Chemistry
Chromate
Exact sciences and technology
Hydrotalcite
Inorganic chemistry and origins of life
Miscellaneous
Molybdate
Preparations and properties
Pyroaurite
Takovite
Thermal analysis
Thermogravimetry
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Summary:The thermal decomposition of hydrotalcites with chromate, molybdate and sulphate in the interlayer has been studied using thermogravimetric analysis coupled to a mass spectrometer measuring the gas evolution. X-ray diffraction shows the hydrotalcites have a d(0 0 3) spacing of 7.98 Å with very small differences in the d-spacing between the three hydrotalcites. XRD was also used to determine the products of the thermal decomposition. For the sulphate-hydrotalcite decomposition the products were MgO and a spinel MgAl 2O 4, for the chromate interlayered hydrotalcite MgO, Cr 2O 3 and spinel. For the molybdate interlayered hydrotalcite the products were MgO, spinel and MgMoO 4. EDX analyses enabled the formula of the hydrotalcites to be determined. Two processes are observed in the thermal decomposition namely dehydration and dehydroxylation and for the case of the sulphate interlayered hydrotalcite, a third process is the loss of sulphate. Both the dehydration and dehydroxylation take place in three steps each for each of the hydrotalcites.
ISSN:0040-6031
1872-762X
DOI:10.1016/j.tca.2005.03.014