Minimization of bauxite residue neutralization products using nanofiltered seawater

Couperthwaite, Sara, Johnstone, Dean, Mullett, Mark, Taylor, Kelvin, & Millar, Graeme J. (2014) Minimization of bauxite residue neutralization products using nanofiltered seawater. Industrial and Engineering Chemistry Research, 53(10), pp. 3787-3794.

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Currently, open circuit Bayer refineries pump seawater directly into their operations to neutralize 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 nanofiltration processes to compare their relative capacities to neutralize bauxite residues. An assessment of the chemical stability of the neutralization products, neutralization 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 neutralization for each technology was determined to be predominately due to the formation of Bayer hydrotalcite and calcium carbonate, however variations in neutralization capacity and efficiencies have been observed. The neutralization efficiency of each feed source has been found to be dependent on the concentration of magnesium, aluminium, calcium and carbonate. Nanofiltered seawater with approximately double the amount of magnesium and calcium required half the volume of seawater to achieve the same degree of neutralization. These studies have revealed that multiple neutralization steps occur throughout the process using characterization techniques such as X-ray diffraction (XRD), infrared (IR) spectroscopy and inductively coupled plasma optical emission spectroscopy (ICP-OES).

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ID Code: 72151
Item Type: Journal Article
Refereed: Yes
Keywords: nanofiltration, bauxite residue, red mud, Bayer process, seawater neutralization
DOI: 10.1021/ie403382z
ISSN: 0888-5885
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 2014 American Chemical Society
Deposited On: 27 May 2014 22:45
Last Modified: 05 Mar 2015 10:22

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