Mechanism and kinetics of iron extraction from high silica boehmite-kaolinite bauxite by hydrochloric acid leaching
(1. Laboratory of Sorption Methods, Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences, 119334 Moscow, Russia;
2. Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia;
3. Department of Non-ferrous Metals Metallurgy, Ural Federal University, 620002 Yekaterinburg, Russia;
4. Tananaev Institute of Chemistry, Kola Science Centre of the Russian Academy of Sciences, 184209 Apatity, Russia;
5. Laboratory of Crystal Structure Studies, A. A. Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, 119334 Moscow, Russia;
6. Universidad Austral de Chile, Valdivia, Chile;
7. Graphite Innovation and Technologies, Dartmouth NS, Canada)
2. Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia;
3. Department of Non-ferrous Metals Metallurgy, Ural Federal University, 620002 Yekaterinburg, Russia;
4. Tananaev Institute of Chemistry, Kola Science Centre of the Russian Academy of Sciences, 184209 Apatity, Russia;
5. Laboratory of Crystal Structure Studies, A. A. Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, 119334 Moscow, Russia;
6. Universidad Austral de Chile, Valdivia, Chile;
7. Graphite Innovation and Technologies, Dartmouth NS, Canada)
Abstract: The chemical and mineral compositions of bauxite recovered from the Severoonezhsk Bauxite Mine (Arkhangelsk region, Russia) were studied by XRD, ICP-OES, TG/DSC, SEM, TEM, and M？ssbauer spectroscopy. The iron-containing minerals of the bauxites were found to comprise alumogoethite (α-Fe1-xAlxOOH), alumohematite (α-(Fe1-xAlx)2O3), alumoakaganeite (β-Fe1-xAlxO(OH,Cl)), and chromite (FeCr2O4). The efficiency of Fe extraction from the bauxite by HCl leaching was 82.5% at 100 °C, HCl concentration of 10%, solid/liquid ratio of 1:10, and the process duration of 60 min, with aluminum loss from the bauxites below 4.5% of the total Al contents in the bauxite. Analysis of the kinetics of the iron leaching process proved diffusion to be the limiting stage of the process at 90-100 °C. Bauxite residue after leaching presented traces of α-Fe1-xAlxOOH and β-Fe1-xAlxO(OH,Cl), and most of the iron content was in the FeCr2O4. In bauxite residue after HCl leaching, in addition to iron oxide, the contents of chromium and calcium oxides significantly decreased. The iron chloride liquor after leaching contained the rare earth elements (REE) of 6.8 mg/L Sc, 4.1 mg/L Ce and 2.3 mg/L Ga.
Key words: bauxite; acid leaching; iron extraction; kinetics; M？ssbauer spectroscopy