Thermal
decomposition of hydronium jarosite (H3O)Fe3(SO4)2(OH)6 |
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Authors: | R L Frost R A Wills J T Kloprogge W N Martens |
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Institution: | (1) Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, Brisbane, Australia, 2434, 4001, Queensland |
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Abstract: | Thermogravimetry combined
with mass spectrometry has been used to study the thermal decomposition of
a synthetic hydronium jarosite. Five mass loss steps are observed at 262,
294, 385, 557 and 619°C. The mass loss step at 557°C is sharp and
marks a sharp loss of sulphate as SO3 from the hydronium
jarosite. Mass spectrometry through evolved gases confirms the first three
mass loss steps to dehydroxylation, the fourth to a mass loss of the hydrated
proton and a sulphate and the final step to the loss of the remaining sulphate.
Changes in the molecular structure of the hydronium jarosite were followed
by infrared emission spectroscopy. This technique allows the infrared spectrum
at the elevated temperatures to be obtained. Infrared emission spectroscopy
confirms the dehydroxylation has taken place by 400 and the sulphate loss
by 650°C. Jarosites are a group of minerals formed in evaporite deposits
and form a component of the efflorescence. The minerals can function as cation
and heavy metal collectors. Hydronium jarosite has the potential to act as
a cation collector by the replacement of the proton with a heavy metal cation. |
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Keywords: | dehydration dehydroxylation high-resolution thermogravimetric analysis hydronium jarosite infrared emission spectroscopy jarosite |
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