Bauxite residue neutralisation precipitate stability in acidic environments

Couperthwaite, Sara, Han, Sujung, Santini, Talitha, Kaur, Gurkiran, Johnstone, Dean, Millar, Graeme and Frost, Ray (2013) Bauxite residue neutralisation precipitate stability in acidic environments. Environmental Chemistry, 10 6: 455-464. doi:10.1071/en13048

Author Couperthwaite, Sara
Han, Sujung
Santini, Talitha
Kaur, Gurkiran
Johnstone, Dean
Millar, Graeme
Frost, Ray
Title Bauxite residue neutralisation precipitate stability in acidic environments
Journal name Environmental Chemistry   Check publisher's open access policy
ISSN 1449-8979
Publication date 2013-01-01
Sub-type Article (original research)
DOI 10.1071/en13048
Volume 10
Issue 6
Start page 455
End page 464
Total pages 10
Place of publication Collingwood, VIC, Australia
Publisher C S I R O Publishing
Language eng
Formatted abstract
This investigation used a combination of techniques, such as X-ray diffraction, inductively coupled plasma optical emission spectroscopy and infrared spectroscopy, to determine the dissolution mechanisms of Bayer precipitate and the associated rate of dissolution in acetic, citric and oxalic acid environments. Bayer precipitate is a mixture of hydrotalcite, calcium carbonate and sodium chloride that forms during the seawater neutralisation of Bayer liquors (waste residue of the alumina industry). The dissolution rate of Bayer precipitate is found to be dependent on 1) the strength of the organic acid and 2) the number of donating H+ ions. The dissolution mechanism for Bayer precipitate consists of a number of steps involving: 1) the dissolution of CaCO3 2) formation of whewellite (calcium oxalate) when oxalic acid is used and 3) multiple dissolution steps for hydrotalcite that are highly dependent on the pH of solution. The decomposition of the Al-OH hydrotalcite layers resulted in the immediate formation of Al(OH)3, which is stable until the pH of solution decreases below 5.5. This investigation has found that Bayer precipitate is stable across a wide pH range in the presence of common organic acids found in the rhizosphere, and that initial decomposition steps are likely to be beneficial in supporting plant growth through the release of nutrients such as Ca2+ and Mg2+.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published: 11 December 2013

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Created: Wed, 13 Nov 2013, 21:31:06 EST by Talitha Santini on behalf of School of Geography, Planning & Env Management