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Minerals 2018, 8(2), 77;

Rare Earth Element Phases in Bauxite Residue

Department of Continuous Improvement and Systems Management, Aluminium of Greece Plant, Metallurgy Business Unit, Mytilineos S.A., Agios Nikolaos, 32003 Boeotia, Greece
School of Mining and Metallurgical Engineering, National Technical University of Athens, Iroon Polytechniou 9, Zografou Campus, 15780 Athens, Greece
Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, P.O. Box 2450, B-3001 Leuven, Belgium
Institute of Physics, University of Tartu, Ostwaldi 1, 50411 Tartu, Estonia
Author to whom correspondence should be addressed.
Received: 30 January 2018 / Revised: 13 February 2018 / Accepted: 15 February 2018 / Published: 24 February 2018
(This article belongs to the Special Issue Bauxite Deposits)
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The purpose of present work was to provide mineralogical insight into the rare earth element (REE) phases in bauxite residue to improve REE recovering technologies. Experimental work was performed by electron probe microanalysis with energy dispersive as well as wavelength dispersive spectroscopy and transmission electron microscopy. REEs are found as discrete mineral particles in bauxite residue. Their sizes range from <1 μm to about 40 μm. In bauxite residue, the most abundant REE bearing phases are light REE (LREE) ferrotitanates that form a solid solution between the phases with major compositions (REE,Ca,Na)(Ti,Fe)O3 and (Ca,Na)(Ti,Fe)O3. These are secondary phases formed during the Bayer process by an in-situ transformation of the precursor bauxite LREE phases. Compared to natural systems, the indicated solid solution resembles loparite-perovskite series. LREE particles often have a calcium ferrotitanate shell surrounding them that probably hinders their solubility. Minor amount of LREE carbonate and phosphate minerals as well as manganese-associated LREE phases are also present in bauxite residue. Heavy REEs occur in the same form as in bauxites, namely as yttrium phosphates. These results show that the Bayer process has an impact on the initial REE mineralogy contained in bauxite. Bauxite residue as well as selected bauxites are potentially good sources of REEs. View Full-Text
Keywords: bauxite; bauxite residue; red mud; rare earth elements; rare earth minerals; rare earth ferrotitanate; perovskite; loparite bauxite; bauxite residue; red mud; rare earth elements; rare earth minerals; rare earth ferrotitanate; perovskite; loparite

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Vind, J.; Malfliet, A.; Blanpain, B.; Tsakiridis, P.E.; Tkaczyk, A.H.; Vassiliadou, V.; Panias, D. Rare Earth Element Phases in Bauxite Residue. Minerals 2018, 8, 77.

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