Bauxite residue neutralisation precipitate stability in acidic environments

Couperthwaite , Sara J., Han, Sujung, Santini, Talitha, Kaur, Gurkiran, Johnstone, Dean W., Millar, Graeme J., & Frost, Ray L. (2013) Bauxite residue neutralisation precipitate stability in acidic environments. Environmental Chemistry, 10(6), pp. 455-464.

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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 the Bayer precipitate and the associated rate of dissolution in acetic, citric and oxalic acid environments. The 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 a 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 a Bayer precipitate consists of several 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 decreases below 5.5. This investigation has found that the 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 Ca2þ and Mg2þ.

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ID Code: 70030
Item Type: Journal Article
Refereed: Yes
Keywords: land remediation, organic acid, red mud
DOI: 10.1071/EN13048
ISSN: 1448-2517
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Structural Chemistry and Spectroscopy (030606)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Journal compilation � CSIRO 2013
Deposited On: 10 Apr 2014 00:58
Last Modified: 11 Aug 2014 23:46

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