Minimization of Bauxite Residue Neutralization Products Using Nanofiltered Seawater

Couperthwaite, Sara J.; Johnstone, Dean W.; Mullett, Mark; Taylor, Kelvin; Millar, Graeme J.

doi:10.1021/ie403382z

Cited by 10 publications

(6 citation statements)

References 21 publications

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“…The residue can be disposed of more safely or be reused in other applications. Calcium chloride and magnesium chloride neutralization (seawater neutralization) of bauxite residue is used by some coastal refineries in Australia (Menzies et al 2009;Santini et al 2011;Couperthwaite et al 2014). Though an excess of NH 4 Cl is required by ammonium chloride neutralization, this technology produces no secondary pollutants.…”

Section: Chloride Salt Neutralizationmentioning

confidence: 99%

Proposal for management and alkalinity transformation of bauxite residue in China

Xue

Kong

Zhu

et al. 2016

Environ Sci Pollut Res

132

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Bauxite residue is a hazardous solid waste produced during the production of alumina. Its high alkalinity is a potential threat to the environment which may disrupt the surrounding ecological balance of its disposal areas. China is one of the major global producers of alumina and bauxite residue, but differences in alkalinity and associated chemistry exist between residues from China and those from other countries. A detailed understanding of the chemistry of bauxite residue remains the key to improving its management, both in terms of minimizing environmental impacts and reducing its alkaline properties. The nature of bauxite residue and the chemistry required for its transformation are still poorly understood. This review focuses on various transformation processes generated from the Bayer process, sintering process, and combined Bayer-sintering process in China. Problems associated with transformation mechanisms, technical methods, and relative merits of these technologies are reviewed, while current knowledge gaps and research priorities are recommended. Future research should focus on transformation chemistry and its associated mechanisms and for the development of a clear and economic process to reduce alkalinity and soda in bauxite residue.

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Section: Chloride Salt Neutralizationmentioning

confidence: 99%

Proposal for management and alkalinity transformation of bauxite residue in China

Xue

Kong

Zhu

et al. 2016

Environ Sci Pollut Res

132

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“…The XRD reflections ascribed to the presence of hydrotalcite did not fit exactly with the reference pattern from the database, which was consistent with the likely formation of several hydrotalcite species (range of Mg:Al: 2:1 at pH > 12, 3:1 at pH ≤ 10, and 4:1 at pH ≤ 8) during neutralization process . In addition, hydrotalcite‐related peaks appeared broad and of relatively low intensity, indicating that relatively small crystals formed …”

Section: Resultsmentioning

confidence: 78%

“…There was evidence for the formation of hydrotalcite (Mg 6 Al 2 (OH) 16 CO 3 ), mixed metal hydroxides (Mg 2 Al(OH) 7 ), calcite (CaCO 3 ), aragonite (CaCO 3 ), and halite (NaCl) in all obtained precipitates based on matches from respective reference patterns. Several studies regarding the seawater neutralization of bauxite refinery residues report similar mineralogical phases . Greater insight regarding the precipitates formed is revealed in Table 1 , which summarized the results of quantitative XRD analysis of the Bayer precipitates.…”

Section: Resultsmentioning

confidence: 95%

“…Therefore, a second magnesium mineralogical phase must be present, which based upon XRD and IR analysis was most probably brucite (Mg(OH) 2 ) . In addition, the elemental analysis of the precipitates revealed that the Mg:Al mass ratio approached 2.7:1 as the concentration of Bayer liquor increased, which was typical for hydrotalcite . Calcium in the precipitates (Table ) was identified by XRD to be calcite and aragonite (Figure ).…”

Section: Resultsmentioning

confidence: 99%

“…Magnesium quantities recorded in the lower Bayer liquor concentrations (1–5 g L −1 ) were greater than predicted from the stoichiometry for hydrotalcite material (i.e., 2.70). Therefore, a second magnesium mineralogical phase must be present, which based upon XRD and IR analysis was most probably brucite (Mg(OH) 2 ) . In addition, the elemental analysis of the precipitates revealed that the Mg:Al mass ratio approached 2.7:1 as the concentration of Bayer liquor increased, which was typical for hydrotalcite .…”

Section: Resultsmentioning

confidence: 99%

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Acid Mine Drainage Treatment Using Bayer Precipitates Obtained from Seawater Neutralization of Bayer Liquor

2018

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Bayer precipitates from the seawater neutralization of Bayer liquor waste from the alumina industry are shown to be a prospective solution for the remediation of acid mine drainage (AMD) water. Precipitates are varied in composition, albeit they are generally comprised of hydrotalcite (Mg 6 Al 2 (OH) 16 CO 3 ∙ x H 2 O), calcite (CaCO 3 ), aragonite (CaCO 3 ), mixed metal hydroxides (Mg 2 Al(OH) 7 ), and halite (NaCl). Brucite (Mg(OH) 2 ) is detected for lower Bayer liquor concentrations (1–3 g L −1 Al 2 O 3 ) when the concentrations of aluminum and hydroxyl species are insufficient to promote hydrotalcite formation. The neutralizing capacity of the precipitates also varies with Bayer liquor composition. Treatment of AMD water with Bayer precipitates met discharge pH guidelines. The dissolution of hydrotalcite and brucite (1–3 g L −1 Bayer precipitates only) is responsible for the Bayer precipitate's neutralizing capacity, while calcium carbonate has a buffering affect at around pH 7. Manganese ions are the most challenging species to remove because high pH values are required (pH > 9), which is not possible with all precipitates tested. One caveat is that increasing the degree of manganese removal generates issues with excessive dissolved aluminum which exceeds discharge limits. Future research should address this latter problem and facilitate implementation of this approach to AMD remediation.

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The potential for constructed wetlands to treat alkaline bauxite residue leachate: laboratory investigations

Buckley

Curtin

Courtney

2016

Environ Sci Pollut Res

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High alkalinity (pH > 12) of bauxite residue leachates presents challenges for the long-term storage and managements of the residue. Whilst the use of constructed wetlands is gaining in interest for its use in the treatment of alkaline waters, thus far, there is limited evidence of its suitability for treating NaOH dominated bauxite residue leachate. A series of batch trials were conducted to investigate the potential for constructed wetland conferred mechanisms (dilution water quality, contact with CO2, and substrate type) for treating NaOH solutions to levels permissible for discharge (p < 9). Results demonstrate that significant reductions in solution pH can be achieved depending on the diluting water quality. Levels achieved may not always be suitable for direct discharge (i.e. pH ≤ 9), but further reductions occur with carbonation and soil contact. The extent of pH decrease and the timeframe required are influenced by soil quality, with greater efficiency observed in soils with higher organic matter content. Decrease in solution pH to discharge permit values are possible through a combination of the mechanisms occurring in a constructed wetland. Formation of a calcite precipitate was observed in some treatments and further characterisation by XRD and XPS suggested surface coating with Na2CO3. It is therefore suggested that, under suitable conditions, constructed wetland technology can reduce leachate pH to <9 through mechanisms supporting the precipitation of sodium carbonate from solution. Further trials should investigate the activity under biological conditions representative of an operating constructed wetland.

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Minimization of Bauxite Residue Neutralization Products Using Nanofiltered Seawater

Cited by 10 publications

References 21 publications

Proposal for management and alkalinity transformation of bauxite residue in China

Proposal for management and alkalinity transformation of bauxite residue in China

Acid Mine Drainage Treatment Using Bayer Precipitates Obtained from Seawater Neutralization of Bayer Liquor

The potential for constructed wetlands to treat alkaline bauxite residue leachate: laboratory investigations

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