Analysis of bauxite residue components responsible for copper removal and related reaction products. (September 2018)

• Record Type: Journal Article
• Authors: Qi, Xuejiao; Wang, Hongtao; Huang, Chenfan; Zhang, Lu; Zhang, Jiyu; Xu, Bolin; Li, Fengting; Araruna, Jose Tacares
• Is Part Of: Chemosphere. Volume 207(2018)
• Page Start: 209
• Page End: 217
• Publication Date: 2018-09
• Subjects: Bauxite residue -- Copper -- Carbonate -- Iron oxide; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2018.05.041
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Bauxite residue is a solid waste produced during alumina production process, and the storage of that in China reached 0.6 billion tons with an increase of more than 70 million annually. Bauxite residue can be used to remove heavy metals from water. This study analyzed components of bauxite residue responsible for copper removal, removal process and accompanying reaction products. Calcite (CaCO3 ), hematite (Fe2 O3 ) and sulfur-Fe are main components contributing to copper removal. Sulfur in bauxite residue works with iron to remove copper. All these components reacted with copper immediately as bauxite residue was added. Reaction time of sulfur-Fe and carbonate was 5 min and 1 h, respectively. And hematite reacted until complete removal of copper (>2 h). Sulfur quickly reacted with coexisting iron to remove copper, producing chalcopyrite (CuFeS2 ), cubanite (CuFe2 S3 ) and bornite (Cu5 FeS4 ). Carbonate in bauxite residue reacted with copper, producing tenorite (CuO), copper hydroxide (Cu(OH)2 ), malachite (Cu2 (OH)2 CO3 ), carbonate cyanotrichite (Cu4 Al2 (CO3, SO4 )(OH)12 ·2H2 O), chalconatronite (Na2 Cu(CO3 )2 ·3H2 O), nakauriite (Cu8 (SO4 )4 (CO3 )(OH)6 ·48H2 O) and callaghanite (Cu2 Mg2 (CO3 )(OH)6 ·2H2 O). Copper precipitated through reaction with hematite to produce delafossite (CuFeO2 ). After removal reaction, the existing forms of copper in bauxite residue comprised carbonate-bound (73.6%–85.7%), iron oxide-bound (5.6%–23.8%), organic matter/sulfide-bound (0.5%–9.0%) and residual forms (0.9%–2.0%). In conclusion, removal of copper using bauxite residue features a more complex reaction than adsorption. Graphical abstract: Image 1 Highlights: Copper removal by red mud is chemical reactions more complex than adsorption. Calcite, hematite and sulfur are responsible for copper removal. Sulfur works with Fe to remove copper. Active components work immediately as red mud added, but reaction time differs. Reaction time of sulfur-Fe, calcite and hematite is 5min, 1 h and >2 h, respectively.