Thermal
decomposition of the synthetic hydrotalcite woodallite |
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Authors: | J M Bouzaid R L Frost A W Musumeci W N Martens |
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Institution: | (1) Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, Queensland, Brisbane, Australia, 4001, GPO Box 2434, 2 George Street |
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Abstract: | The thermal
stability and thermal decomposition pathways for synthetic woodallite have
been determined using thermogravimetry in conjunction with evolved gas mass
spectrometry. Chemical analysis showed the formula of the synthesised woodallite
to be Mg6.28Cr1.72Cl(OH)16(CO3)0.36⋅8.3H2O and X-ray diffraction confirms the layered
LDH structure. Dehydration of the woodallite occurred at 65°C. Dehydroxylation
occurred at 302 and 338°C. Both steps were associated with the loss of
carbonate. Hydrogen chloride gas was evolved over a wide temperature range
centred on 507°C. The products of the thermal decomposition were MgO and
a spinel MgCr2O4. Experimentally
it was found to be difficult to eliminate CO2 from
inclusion in the interlayer during the synthesis of the woodallite compound
and in this way the synthesised woodallite resembled the natural mineral. |
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Keywords: | dehydration dehydroxylation high-resolution thermogravimetry hydrotalcite iowaite woodallite |
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