scholarly journals Rare Earth Element Phases in Bauxite Residue

2018 ◽  
Author(s):  
Johannes Vind ◽  
Annelies Malfliet ◽  
Bart Blanpain ◽  
Petros E. Tsakiridis ◽  
Alan H. Tkaczyk ◽  
...  
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Bauxite Residue ◽  
Bayer Process ◽  
Minor Amount ◽  
Secondary Phases ◽  
Wavelength Dispersive Spectroscopy ◽  
Natural Systems

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.

Effect of Conjoint Additions of Rare Earth Element Oxides on the Phase Stability of Zirconia

1995 ◽  
Vol 412 ◽  
Author(s):  
Ewan R. Maddrell
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Oxide Phase ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zirconium Butoxide ◽  
Pyrochlore Type

AbstractThe ability of the cubic phase of zirconia to accommodate in solid solution the oxides of rare earth elements with differing cationic radii has been investigated. Mixed oxide phase assemblages were prepared by hydrolysing zirconium butoxide with solutions of rare earth element nitrates followed by drying, calcining and sintering. The resulting products were characterised by X-ray diffraction and energy dispersive spectroscopy. The cubic zirconia phase can accept into solid solution the larger, non-cubic stabilising, rare earth element ions such as lanthanum in the presence of the cubic stabilising oxides of yttrium and samarium. As the proportion of the larger rare earth element ions is increased the formation of pyrochlore type compounds is favoured.

scholarly journals Rare Earth Element Phases in Bauxite Residue

Minerals ◽  
2018 ◽  
Vol 8 (2) ◽  
pp. 77 ◽  
Author(s):  
Johannes Vind ◽  
Annelies Malfliet ◽  
Bart Blanpain ◽  
Petros Tsakiridis ◽  
Alan Tkaczyk ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Bauxite Residue

Quadrivalent praseodymium in planetary materials

2020 ◽  
Vol 105 (12) ◽  
pp. 1802-1811
Author(s):  
Michael Anenburg ◽  
Antony D. Burnham ◽  
Jessica L. Hamilton
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Rare Earth Element ◽  
Earth Element ◽  
Atacama Desert ◽  
Light Rare Earth ◽  
Ionic Radii ◽  
Natural Systems ◽  
Geological Conditions ◽  
Almost All

Abstract Praseodymium is capable of existing as Pr3+ and Pr4+. Although the former is dominant across almost all geological conditions, the observation of Pr4+ by XANES and Pr anomalies (both positive and negative) in multiple light rare earth element minerals from Nolans Bore, Australia, and Stetind, Norway, indicates that quadrivalent Pr can occur under oxidizing hydrothermal and supergene conditions. High-temperature REE partitioning experiments at oxygen fugacities up to more than 12 log units more oxidizing than the fayalite-magnetite-quartz buffer show negligible evidence for Pr4+ in zircon, indicating that Pr likely remains as Pr3+ under all magmatic conditions. Synthetic Pr4+-bearing zircons in the pigment industry form under unique conditions, which are not attained in natural systems. Quadrivalent Pr in solutions has an extremely short lifetime, but may be sufficient to cause anomalous Pr in solids. Because the same conditions that favor Pr4+ also stabilize Ce4+ to a greater extent, these two cations have similar ionic radii, and Ce is more than six times as abundant as Pr, it seems that Pr-dominant minerals must be exceptionally rare if they occur at all. We identify cold, alkaline, and oxidizing environments such as oxyhalide-rich regions at the Atacama Desert or on Mars as candidates for the existence of Pr-dominant minerals.

scholarly journals The occurrence of wakefieldite, a rare earth element vanadate, in the rhyolitic Joe Lott Tuff, Utah, USA

2019 ◽  
Vol 84 (1) ◽  
pp. 109-116
Author(s):  
Bogusław Bagiński ◽  
Ray Macdonald ◽  
Harvey E. Belkin ◽  
Jakub Kotowski ◽  
Petras Jokubauskas ◽  
...  
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Hydrothermal Fluid ◽  
Earth Element ◽  
Hydrothermal Fluids ◽  
Fe Oxide ◽  
Uranium Mineralisation ◽  
High Silica

AbstractThe high-silica rhyolitic Joe Lott Tuff was erupted at 19.2 ± 0.4 Ma from the Mount Belknap caldera, SW Utah. Certain units in the tuff contain two species of wakefieldite, the Nd- and Y-dominant types. They occur in disseminated streaks and patches in association with rhodochrosite, calcite, Fe oxide, cerite-(Ce), and a Mn silicate (caryopilite?), thought to have been deposited from hydrothermal fluids. The wakefieldites contain the highest levels of As (≤15.34 wt.% As2O5) and P (≤5.7 wt.% P2O5) yet recorded in this mineral, indicating significant solid solution towards chernovite-(Y) and xenotime-(Y). Thorium levels are also unusually high (≤14.2 wt.% ThO2). The source of the hydrothermal fluid(s) is unknown but might be related to uranium mineralisation in the region, in that As, V and U are commonly associated in such deposits.

Ceramic Wasteforms for the Conditioning of Spent MOx Fuel Wastes

2003 ◽  
Vol 807 ◽  
Author(s):  
E. R. Maddrell ◽  
P. K. Abraitis
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Fission Product ◽  
Rare Earth Element ◽  
Earth Element ◽  
Fission Products ◽  
Waste Stream ◽  
Mox Fuel ◽  
Radiation Resistant ◽  
Crystalline Ceramic

ABSTRACTCrystalline ceramic wasteforms have been fabricated to immobilise a combined fission product and actinide waste stream arising from spent MOx fuel. The fuel is conditioned by a UREX process, as contrasted to PUREX, to produce a waste stream containing fission products and transuranics. Zirconia rich Synroc derivatives have been formulated to minimise formation of perovskite. This ensures that the transuranics are predominantly immobilised in zirconolite. For comparison, a wasteform has also been produced in which transuranics and rare earth element fission products are immobilised in a radiation resistant cubic zirconia solid solution, whilst caesium, strontium and barium are partitioned to an alumina rich magnetoplumbite phase.

scholarly journals Selective rare earth element extraction using high-pressure acid leaching of slags arising from the smelting of bauxite residue

2019 ◽  
Vol 184 ◽  
pp. 162-174 ◽  
Author(s):  
Rodolfo Marin Rivera ◽  
Buhle Xakalashe ◽  
Ghania Ounoughene ◽  
Koen Binnemans ◽  
Bernd Friedrich ◽  
...  
Keyword(s):  
High Pressure ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Bauxite Residue ◽  
Acid Leaching ◽  
Pressure Acid Leaching
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