Rare Earth Element Phases in Bauxite Residue

Vind, Johannes; Malfliet, Annelies; Blanpain, Bart; Tsakiridis, P.E.; Tkaczyk, Alan H.; Vassiliadou, Vicky; Panias, Dimitrios

doi:10.3390/min8020077

Cited by 63 publications

(67 citation statements)

References 65 publications

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“…Small REEs-containing particles (about 10 µm) were detected in SEM-EDS, in particular YPO 4 particles including heavy rare earths like gadolinium and dysprosium (Figure 9 left). This is consistent with Vind et al studies of raw bauxite residue [39] where the presence of heavy rare earth phosphates with the major constituent being yttrium and containing other heavy REEs like gadolinium, dysprosium, and erbium is reported. This is an indication that these grains endure the [Emim][HSO 4 ] leaching process without being subjected to any dissolution and thus explaining negligible heavy REEs recoveries.…”

Section: Rees In the Solid Residuesupporting

confidence: 92%

Scandium and Titanium Recovery from Bauxite Residue by Direct Leaching with a Brønsted Acidic Ionic Liquid

Bonomi

Alexandri

Vind

et al. 2018

Metals

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In this study, bauxite residue was directly leached using the Brønsted acidic ionic liquid 1-ethyl-3-methylimidazolium hydrogensulfate. Stirring rate, retention time, temperature, and pulp density have been studied in detail as the parameters that affect the leaching process. Their optimized combination has shown high recovery yields of Sc, nearly 80%, and Ti (90%), almost total dissolution of Fe, while Al and Na were partially extracted in the range of 30-40%. Si and rare earth element (REEs) dissolutions were found to be negligible, whereas Ca was dissolved and reprecipitated as CaSO 4 . The solid residue after leaching was fully characterized, providing explanations for the destiny of REEs that remain undissolved during the leaching process. The solid residue produced after dissolution can be further treated to extract REEs, while the leachate can be subjected to metal recovery processes (i.e., liquid-liquid extraction) to extract metals and regenerate ionic liquid. been listed as a critical raw material by the European Commission due to its high economic importance and supply risk [11]. In fact, Sc is mainly produced as a byproduct during the processing of various ores, from titanium and REEs ores (China), uranium ore (Kazakhstan and Ukraine), and apatite ore (Russia). It can also be recovered from previously processed tailings or residues [9,12,13]. For these reasons, BR can be accounted as a secondary raw material source [14], and the recovery of Sc could represent a high economic interest.BR can also be considered a secondary source for Ti, which is a photocatalyst and it is applied in the white pigment industry [15]. Since the availabilities and qualities of Ti ores are decreasing [16], it is important to find methods for extracting Ti from secondary sources.Many studies, patents, and pilot scale implementations have been carried out for Sc and Ti recovery from BR, mainly by investigating hydrometallurgical or combined pyro-hydrometallurgical processes [5,12,[16][17][18][19][20][21][22][23], but none of them has reached an industrial scale. Nowadays, the impact of the zero-waste valorization policy motivates the research community on finding innovative, greener, and economical viable routes for metal extraction from complex polymetallic matrices, such as the bauxite residue [24].Ionometallurgical approach can be exploited as an alternative to conventional hydrometallurgical processing. The term ionometallurgy indicates the use of ionic liquids (ILs) as solvents in metals processing. ILs are liquid at room temperature and consist solely of ions; generally an organic cation and inorganic/organic anion. ILs have superior properties against conventional organic solvents, such as nonflammability, a wide electrochemical window, high thermal stability, negligible vapor pressure, and low volatility [25]. For these reasons and thanks to the vast number of combinations of the cation and the anion during synthesis, ILs have potential for many applications, such as solvent extraction [26,27], catalytic reactions [28,...

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Section: Rees In the Solid Residuesupporting

confidence: 92%

Scandium and Titanium Recovery from Bauxite Residue by Direct Leaching with a Brønsted Acidic Ionic Liquid

Bonomi

Alexandri

Vind

et al. 2018

Metals

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“…Other metals, such as Ce, La or Y that were of high interest within the scope of this study, do not occur in dissolved form in Bayer liquor in detectable concentrations (Table 3). This is to be expected as the REEs are not predicted to have soluble species in highly alkaline conditions (pH > 14) [58,59], which is further supported by the mineralogical observations indicating the REEs remain in solid forms during the Bayer digestion [60]. For the case of Sc, INAA found its levels being <0.05 mg/L, which is in accordance with Suss et al who report that Sc concentration in Bayer liquor remains <1 mg/L [13].…”

Section: Resultssupporting

confidence: 78%

“…None of the REEs or Sc enter into aluminium hydroxide, given the available detection limits, e.g., La < 0.5 mg/kg, Sm <0.1 mg/kg or Sc < 0.1 mg/kg (Supplementary Table S2). The fact that REEs and Sc are transferred to bauxite residue only in the composition of solid material is also supported by mineralogical studies [60,77]. One of the investigations has shown that the form of Sc occurrence mainly in the composition of hematite remains the same after bauxite processing [77].…”

Section: Metals That Do Not Accumulate To Liquormentioning

confidence: 56%

“…One of the investigations has shown that the form of Sc occurrence mainly in the composition of hematite remains the same after bauxite processing [77]. On the other hand, the precursor REE phases found in bauxite are affected by the Bayer process conditions and REE ferrotitanate type compounds are created, but the transformations taking place seem to occur in situ on mineral grain surfaces without the dissolution of the precursor REE phases [60]. Present case study was not able to repeat the result that up to five percent of total La content can be passed to aluminium hydroxide product [25].…”

Section: Metals That Do Not Accumulate To Liquormentioning

confidence: 99%

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Distribution of Selected Trace Elements in the Bayer Process

Vind

Alexandri

Vassiliadou³

et al. 2018

Metals

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Abstract:The aim of this work was to achieve an understanding of the distribution of selected bauxite trace elements (gallium (Ga), vanadium (V), arsenic (As), chromium (Cr), rare earth elements (REEs), scandium (Sc)) in the Bayer process. The assessment was designed as a case study in an alumina plant in operation to provide an overview of the trace elements behaviour in an actual industrial setup. A combination of analytical techniques was used, mainly inductively coupled plasma mass spectrometry and optical emission spectroscopy as well as instrumental neutron activation analysis. It was found that Ga, V and As as well as, to a minor extent, Cr are principally accumulated in Bayer process liquors. In addition, Ga is also fractionated to alumina at the end of the Bayer processing cycle. The rest of these elements pass to bauxite residue. REEs and Sc have the tendency to remain practically unaffected in the solid phases of the Bayer process and, therefore, at least 98% of their mass is transferred to bauxite residue. The interest in such a study originates from the fact that many of these trace constituents of bauxite ore could potentially become valuable by-products of the Bayer process; therefore, the understanding of their behaviour needs to be expanded. In fact, Ga and V are already by-products of the Bayer process, but their distribution patterns have not been provided in the existing open literature.

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“…Bauxite residues are solid-solution mixtures ranging in initial solids content from 20% to 80% by weight (depending on the disposal method of the refinery) characterized by high pH (up to 13), a high sodium (Na + ) content and electrical conductivity (EC). 75,76 Roughly 70% of the solid bauxite residue is in a crystalline phase, 75 including primary mineral phases which are those that are already present in bauxite (e.g. hematite, diaspore, boehmite and goethite) and secondary mineral phases which are formed during the Bayer process, such as hydrogarnet, cancrinite, perovskite and gibbsite.…”

Section: Bauxite Residue Compositionmentioning

confidence: 99%

Re‐using bauxite residues: benefits beyond (critical raw) material recovery

Ujaczki

Feigl

Molnár

et al. 2018

J of Chemical Tech & Biotech

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Since the world economy has been confronted with an increasing risk of supply shortages of critical raw materials (CRMs), there has been a major interest in identifying alternative secondary sources of CRMs. Bauxite residues from alumina production are available at a multi‐million tonnes scale worldwide. So far, attempts have been made to find alternative re‐use applications for bauxite residues, for instance in cement / pig iron production. However, bauxite residues also constitute an untapped secondary source of CRMs. Depending on their geological origin and processing protocol, bauxite residues can contain considerable amounts of valuable elements. The obvious primary consideration for CRM recovery from such residues is the economic value of the materials contained. However, there are further benefits from re‐use of bauxite residues in general, and from CRM recovery in particular. These go beyond monetary values (e.g. reduced investment / operational costs resulting from savings in disposal). For instance, benefits for the environment and health can be achieved by abatement of tailing storage as well as by reduction of emissions from conventional primary mining. Whereas certain tools (e.g. life‐cycle analysis) can be used to quantify the latter, other benefits (in particular sustained social and technological development) are harder to quantify. This review evaluates strategies of bauxite residue re‐use / recycling and identifies associated benefits beyond elemental recovery. Furthermore, methodologies to translate risks and benefits into quantifiable data are discussed. Ultimately, such quantitative data are a prerequisite for facilitating decision‐making regarding bauxite residue re‐use / recycling and a stepping stone towards developing a zero‐waste alumina production process. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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Rare Earth Element Phases in Bauxite Residue

Cited by 63 publications

References 65 publications

Scandium and Titanium Recovery from Bauxite Residue by Direct Leaching with a Brønsted Acidic Ionic Liquid

Scandium and Titanium Recovery from Bauxite Residue by Direct Leaching with a Brønsted Acidic Ionic Liquid

Distribution of Selected Trace Elements in the Bayer Process

Re‐using bauxite residues: benefits beyond (critical raw) material recovery

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