Preprint Article Version 1 This version is not peer-reviewed

Rare Earth Element Phases in Bauxite Residue

Version 1 : Received: 30 January 2018 / Approved: 30 January 2018 / Online: 30 January 2018 (20:42:31 CET)

A peer-reviewed article of this Preprint also exists.

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. 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.

Journal reference: Minerals 2018, 8, 77
DOI: 10.3390/min8020077

Abstract

The purpose of present work was to provide mineralogical insight in 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. Comparing 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 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.

Subject Areas

bauxite; bauxite residue; red mud; rare earth elements; rare earth minerals; rare earth ferrotitanate; perovskite; loparite

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