A Study of the Occurrence of Selected Rare-Earth Elements in Neutralized–Leached Bauxite Residue and Comparison with Untreated Bauxite Residue
This study investigates the chemical associations of the selected rare-earth elements (Sc, Y, Ce, La, and Nd) with major element phases in the postprocessed bauxite residues and compares them with the untreated bauxite residue. The treatment of bauxite residue considers our previous published process which involved the neutralization with CO2, followed by leaching with H2SO4. Neutralized bauxite residue resulted with larger aggregates than the untreated bauxite residue after making contact with CO2 as the consequence of additional CaCO3 formation. Neutralization with CO2, however, has a negligible effect on the distribution of the rare-earth elements (REEs) with respect to the untreated bauxite residue, but a large amount of rare earths remained unreacted after acid leaching. Electron probe microanalysis (EPMA) confirmed the chemical associations of Sc(III) and Ce(IV) with Fe(III)- and Al(III)-containing minerals in the postprocessed bauxite residues, i.e., bauxite residues subjected to CO2-neutralization and neutralization–acid leaching processes. The occurrence of Nd(III) is positively correlated to that of La(III) in the untreated bauxite residue, but both of them may be associated with the same mineralogical phase as Ce(IV) after processing. Y(III) may remain associated with the Al/Si-minerals, cancrinite and chamosite. Ergo, the extractability of Sc, Y, Ce, La, and Nd from neutralized bauxite residue is more difficult in H2SO4 media due to the presence of coarser particles compared to those of the untreated bauxite residue, but also due to the formation of a solid product layer (i.e., CaSO4) that is presumably adsorbed on the surface of Fe(III)-rich phases (hematite and goethite) and Al(III)-containing minerals (diaspore, gibbsite, boehmite, and chamosite).
KeywordsBauxite residue Carbon dioxide Electron probe microanalysis Rare earths Red mud
The above research leading to these results has received funding from the European Community’s Horizon 2020 Programme (H2020/2014–2019) under Grant Agreement No. 636876 (MSCA- ETN REDMUD). This publication reflects only the authors’ view, exempting the Community from any liability. Project website: http://www.etn.redmud.org.
- 5.Deady E, Mouchos E, Goodenough K, et al (2014) Rare earth elements in karst-bauxites: a novel untapped European resource? In: ERES2014: 1st European Rare Earth Resources Conference (Milos, Greece, 4–7 September 2014). pp 364–375Google Scholar
- 8.Kaya S, Topkaya YA (2015) Extraction behavior of scandium from a refractory nickel laterite ore during the pressure acid leaching process. In: Rare earths industry: technological, economic, and environmental implications. pp 177–188Google Scholar
- 14.Patterson SH, Kurtz HF, Olson JC, Neeley CL (1986) World Bauxite Resources. In: U.S. Geological Survey professional paper. WashingtonGoogle Scholar
- 15.Vind J, Vassiliadou V, Panias D (2017) Distribution of trace elements through the bayer process and its by-products. In: 35th International ICSOBA Conference, Hamburg, Germany, Oct 2–5, 2017. pp 255–267Google Scholar
- 18.Bánvölgyi GG (2016) Scale Formation in Alumina Refineries. In: Travaux 45, Proceedings of 34th International ICSOBA Conference. Quebec, pp 1–14Google Scholar
- 19.Suss A, Kuznetsova N V, Kozyrev A, Panov A (2017) Specific Features of Scandium Behavior during Sodium Bicarbonate Digestion of Red Mud. In: 35th International ICSOBA Conference, Hamburg, Germany, October 2–5, 2017. pp 491–504Google Scholar
- 32.Urbain G, Sarkar PB (1927) Sur les analogies du scandium avec les éléments des terres rares et avec les éléments trivalents de la famille du fer. Compt Rend 185:593–596Google Scholar
- 34.Sajó IE (2008) X-ray diffraction quantitative phase analysis of bayer process solids. International ICSOBA Conference. Bhubaneswar, India, pp 71–76Google Scholar
- 36.Rao BH, Reddy NG (2017) Zeta potential and particle size characteristics of red mud waste. Geoenvironmental practices and sustainability. Springer Nature Singapore Pte Ltd., Odisha, pp 69–89Google Scholar
- 55.Myerson A (2002) Handbook of Industrial Crystallization, second edition. BostonGoogle Scholar