Abstract
The precipitate formed during the seawater neutralization (SWN) of Bayer liquors has been characterized by a variety of techniques, including X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma−optical emission spectroscopy (ICP-OES), infrared and Raman spectroscopy, and thermal analysis. Three mineralogical phases are detected: (1) hydrotalcite, (2) calcite (CaCO3), and (3) aragonite (CaCO3). It is proposed that two hydrotalcite structures form and have the formulas Mg8Al2(OH)12(CO32−,SO42−)·xH2O and Mg6Al2(OH)16(CO32−,SO42−)·xH2O. The Mg, Al molar ratio of the Bayer hydrotalcite is dependent on both the pH and the composition of the initial Bayer liquor. It is proposed that carbonate and sulfate ions are intercalated predominantly into the hydrotalcite interlayer; however, small amounts of arsenate, vanadate, and molybdate have been shown to be removed from solution. The formation of Bayer hydrotalcite assists in the removal of oxy-anions of transition metals ...
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