Improvements to bauxite residue neutralisation efficiency through the use of alternative feed sources

Johnstone, Dean W., Couperthwaite, Sara J., Mullett, Mark, & Millar, Graeme J. (2013) Improvements to bauxite residue neutralisation efficiency through the use of alternative feed sources. In Chemeca 2013: Challenging Tomorrow, Engineers Australia, Brisbane Convention & Exhibition Centre, Queensland, QLD, pp. 107-113.

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Currently, open circuit Bayer refineries pump seawater directly into their operations to neutralise the caustic fraction of the Bayer residue. The resulting supernatant has a reduced pH and is pumped back to the marine environment. This investigation has assessed modified seawater sources generated from different ion filtration processes to compare their relative capacities to neutralise bauxite residues. An assessment of the chemical stability of the neutralisation products, neutralisation efficiency, discharge water quality, bauxite residue composition, and associated economic benefits have been considered to determine the most preferable seawater filtration process based on implementation costs, savings to operations and environmental benefits.

The mechanism of neutralisation for each technology was determined to be predominately due to the formation of Bayer hydrotalcite and calcium carbonate, however variations in neutralisation capacity and efficiencies have been observed. The neutralisation efficiency of each feed source has been found to be dependent on the concentration of magnesium, aluminium, calcium and carbonate. These studies have revealed that multiple neutralisation steps occur throughout the process.

Environmental, economic and social advantages and disadvantages of the different filtration technologies have been explored to determine the most sustainable method for the neutralisation of bauxite residues. The relative degree of “green” associated with nanofiltered seawater and reverse osmosis filtered seawater are discussed.

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ID Code: 72153
Item Type: Conference Paper
Refereed: Yes
Additional URLs:
Keywords: bauxite residue, brine, nanofiltration, reverse osmosis, seawater neutralisation
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > INORGANIC CHEMISTRY (030200)
Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > ENVIRONMENTAL ENGINEERING (090700)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2013 [please consult the author]
Deposited On: 27 May 2014 22:55
Last Modified: 30 May 2014 06:50

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