Hydrotalcites and their role in coordination of anions in Bayer liquors: Anion binding in layered double hydroxides

✍ Scribed by Sara J. Palmer; Ray L. Frost; Tai Nguyen

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 791 KB
• Volume: 253
• Category: Article
• ISSN: 0010-8545
• DOI: 10.1016/j.ccr.2008.01.012

✦ Synopsis

Bauxite refinery residues (red mud) are derived from the Bayer process by the digestion of crushed bauxite in concentrated caustic at elevated temperatures and pressures. Following the recovery of the valuable alumina containing portion, there remains an alkaline residue consisting primarily of iron oxides, aluminium oxides, silica oxides, titanium oxides and trace heavy metals. This slurry residue, if untreated, is unsuitable for discharge directly into the environment and is usually stored in holding dams. The liquid portion has the potential for discharge, but requires pre-treatment before this can occur. Seawater neutralisation of the solid residue is one such treatment which has been employed in recent years. This process facilitates a significant reduction in pH and dissolved metal concentrations, through the precipitation of hydrotalcite-like compounds and some other Mg, Ca, and Al hydroxide and carbonate minerals. The hydrotalcite-like compounds, precipitated during seawater neutralisation,