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

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 (MgAl(OH)CO∙HO), calcite (CaCO), aragonite (CaCO), mixed metal hydroxides (MgAl(OH)), and halite (NaCl). Brucite (Mg(OH)) is detected for lower Bayer liquor concentrations (1-3 g L AlO) when the concentrations of aluminum and hydroxyl species are insufficient to promote hydrotalcite formation.

Effect of strong acids on red mud structural and fluoride adsorption properties.

The removal of fluoride using red mud has been improved by acidifying red mud with hydrochloric, nitric and sulphuric acid. The acidification of red mud causes sodalite and cancrinite phases to dissociate, confirmed by the release of sodium and aluminium into solution as well as the disappearance of sodalite bands and peaks in infrared and X-ray diffraction data. The dissolution of these mineral phases increases the amount of available iron and aluminium oxide/hydroxide sites that are accessible for the adsorption of fluoride.

A review of the removal of anions and oxyanions of the halogen elements from aqueous solution by layered double hydroxides.

The application of layered double hydroxides (LDHs) and thermally activated LDHs for the removal of various fluorine (F(-),BF4(-)), chlorine (Cl(-),ClO4(-)), bromine (Br(-),BrO3(-)) and iodine (I(-),IO3(-)) species from aqueous solutions has been reviewed in this article. LDHs and thermally activated LDHs were able to significantly reduce the concentration of selected anions in laboratory scale experiments. The M(2+):M(3+) cation ratio of the LDH adsorbent was an important factor which influenced anion uptake.

A Raman spectroscopic study of the basic carbonate mineral callaghanite Cu2Mg2(CO3)(OH)6·2H2O.

Raman spectrum of callaghanite, Cu2Mg2(CO3)(OH)6·2H2O, was studied and compared with published Raman spectra of azurite, malachite and hydromagnesite. Stretching and bending vibrations of carbonate and hydroxyl units and water molecules were tentatively assigned. Approximate O-H…O hydrogen bond lengths were inferred from the spectra.

Adsorption of reactive dye on seawater-neutralised bauxite refinery residue.

This investigation has demonstrated the need for thermal treatment of seawater neutralised red mud (SWRM) in order to obtain reasonable adsorption of Reactive Blue dye 19 (RB 19). Thermal treatment results in a greater surface area, which results in an increased adsorption capacity due to more available adsorption sites. Adsorption of RB 19 has been found to be best achieved in acidic conditions using SWNRM400 (heated to 400°C) with an adsorption capacity of 416.

Vibrational spectroscopic study of multianion mineral clinotyrolite Ca₂Cu9[(As,S)O₄]₄(OH)10·10(H₂O).

The molecular structure of the mixed anion mineral clinotyrolite Ca(2)Cu(9)[(As,S)O(4)](4)(OH)(10)·10(H(2)O) has been determined by the combination of Raman and infrared spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands.