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

Gurkiran Kaur,Graeme J. Millar,Sara J. Couperthwaite

doi:10.1002/gch2.201800061

Gurkiran Kaur, Graeme J. Millar + Show 1 more

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https://doi.org/10.1002/gch2.201800061

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Abstract

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 (Mg6Al2(OH)16CO3∙xH2O), calcite (CaCO3), aragonite (CaCO3), mixed metal hydroxides (Mg2Al(OH)7), and halite (NaCl). Brucite (Mg(OH)2) is detected for lower Bayer liquor concentrations (1–3 g L−1 Al2O3) 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.

Highlights

Introduction reduction in bothpH and dissolved metal concentrations.[11,12] Seawater neutralization of bauxite refinery residue results in theThe Bayer process developed and patented by Karl Joseph Bayer reduction of alkalinity through the precipitation of Mg, Ca, and 110 years ago is used for refining bauxite ore into smelting Al hydroxides and carbonate minerals.[10,11,13,14] The primary grade alumina (Al2O3)
This research has shown that the composition of Bayer precipitates were key to the degree of neutralization and metal removal in acid mine drainage (AMD) waters
The research provides a deeper understanding of the chemical reactions involved in (1) the dissolution of Bayer precipitates, and (2) the treatment of AMD water using Bayer precipitate dissolution species

Summary

Introduction

Introduction reduction in bothpH and dissolved metal concentrations.[11,12] Seawater neutralization of bauxite refinery residue results in theThe Bayer process developed and patented by Karl Joseph Bayer reduction of alkalinity through the precipitation of Mg, Ca, and 110 years ago is used for refining bauxite ore into smelting Al hydroxides and carbonate minerals.[10,11,13,14] The primary grade alumina (Al2O3). Seawater neutralization of bauxite refinery residue results in the. The Bayer process developed and patented by Karl Joseph Bayer reduction of alkalinity through the precipitation of Mg, Ca, and 110 years ago is used for refining bauxite ore into smelting Al hydroxides and carbonate minerals.[10,11,13,14]. The Bayer process involves the diges- pathway of the seawater neutralization process is the formation tion of bauxite in concentrated caustic at high temperatures of Bayer hydrotalcite, a stable alkaline precipitate consisting of positively charged metal hydroxide layers (Mg and Al) which are. Millar Chemistry, Physics, Mechanical Engineering, Science and Engineering Faculty Queensland University of Technology (QUT)

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