Influence of hydration variables on the properties of South African calcium/siliceous-based material |
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Authors: | DOOGENGA ZOSIAGI MSONYANGO MMBARAWA |
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Affiliation: | (1) Department of Mechanical Engineering, Pretoria Campus, Tshwane University of Technology, Private Bag X680, 0001 Pretoria, South Africa;(2) Department of Chemical and Metallurgical, Pretoria Campus, Tshwane University of Technology, Private Bag X680, 0001 Pretoria, South Africa |
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Abstract: | This study presents findings from experiments on the preparation and characterization of locally available fly ash, quicklime
and the CaO/fly ash sorbent, synthesized using the atmospheric hydration process. The CaO was obtained from calcination of
limestone in a laboratory kiln at a temperature of 900°C. The sorbents were prepared under different hydration conditions:
CaO/fly ash weight ratio (1°1 to 1°3), hydration temperature (55°C–75°C) and hydration period (4–8 h). Results show that the
specific surface area of CaO/ fly ash sorbents (8.8–23.6 m2/g) was higher than that of the CaO (4.78 m2/g) at all preparation conditions. The SEM micrographs show that the prepared sorbent had a more porous structure than either
the fly ash or the CaO. The X-ray diffraction (XRD) analysis shows the presence of complex compounds containing calcium silicate
hydrate in the synthesized sorbents. This contributed to the high BET specific surface area. The Brunauer-Emmett-Teller (BET)
specific surface area was found to decrease with increase in the amount of fly ash with the ratio of 1:1 (CaO/Fly ash) giving
the highest value. It was also found that an increase in the hydration time resulted in an increased BET specific surface
area, although there was only a slight effect on the same by an increase in temperature. |
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Keywords: | fly ash calcium oxide desulphurization hydration variables quicklime sorbents |
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