IUPAC-NIST Solubility Data Series. 100. Rare Earth Metal Fluorides in Water and Aqueous Systems. Part 1. Scandium Group (Sc, Y, La)

Mioduski, T.; Gumiński, C.; Zeng, Dewen

doi:10.1063/1.4866773

Cited by 26 publications

(22 citation statements)

References 40 publications

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“…The overall stability constant of ScF 6 3− was extrapolated and approximated from the constants of the lower Sc-F complexes, since they had a perfect quadratic fit. The existence of the pentafluoride complex, ScF 5 2− , was only mentioned briefly [20] with no adequate information available in other sources. There is also evidence of the polynuclear complex, Sc 2 F 3 3+ [25].…”

Section: Thermodynamic Modelingmentioning

confidence: 99%

“…The high stripping efficiency of scandium with 3 mol/L NH 4 F solution is due to the complexation of scandium and fluoride ions in high concentration of ammonium fluoride media [20,[31][32][33][34] according to the following extraction and stripping reactions Equations (1) and (2)…”

Section: Strip Liquor Preparationmentioning

confidence: 99%

“…There is information about the crystallization of scandium fluoride phases in literature. Scandium can be precipitated from an ammonium fluoride solution as ScF 3 ·(0-0.25)H 2 O, NH 4 ScF 4 , (NH 4 ) 3 ScF 6 , (NH 4 ) 5 Sc 3 F 14 , NH 4 Sc 3 F 10 or (NH 4 ) 2 Sc 3 F 11 , depending on the composition of the solution and temperature [18][19][20]. Scandium could also be precipitated as sodium or potassium fluoride and ammonium fluoride salts [19].…”

Section: Introduction-previous Studies and State Of The Artmentioning

confidence: 99%

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Scandium Recovery from an Ammonium Fluoride Strip Liquor by Anti-Solvent Crystallization

Kaya¹,

Peters²,

Forsberg³

et al. 2018

Metals

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In this study, the crystallization of scandium from ammonium fluoride strip liquor, obtained by solvent extraction, was investigated using an anti-solvent crystallization technique. Acetone, ethanol, methanol and isopropanol were added individually to the strip liquor as the anti-solvent and scandium was precipitated and obtained in the form of (NH 4 ) 3 ScF 6 crystals. The results show that scandium can be effectively crystallized from the strip liquor to obtain an intermediate, marketable scandium product. Yields greater than 98% were obtained using an anti-solvent to strip liquor volumetric ratio of 0.8. Acetone had the least performance at lower anti-solvent to strip liquor volumetric ratios, possibly due to its limited H bonding capability with water molecules when compared to alcohols.

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Section: Thermodynamic Modelingmentioning

confidence: 99%

Section: Strip Liquor Preparationmentioning

confidence: 99%

Section: Introduction-previous Studies and State Of The Artmentioning

confidence: 99%

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Scandium Recovery from an Ammonium Fluoride Strip Liquor by Anti-Solvent Crystallization

Kaya¹,

Peters²,

Forsberg³

et al. 2018

Metals

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“…The stability constants of complexes are mainly available for purely aqueous systems and not for solvent mixtures. The stability constants of Sc fluoride complexes [28] as well as the solubility product of ScF 3 [29] in aqueous solutions have been published. In addition, the solubilities of ScF 3 and (NH 4 ) 3 ScF 6 have been determined in HF-dosed solutions [30].…”

Section: Introductionmentioning

confidence: 99%

Recovery of Scandium by Crystallization Techniques

Peters

Kaya

Dittrich

et al. 2019

J. Sustain. Metall.

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Bauxite residues, i.e., red mud, can be processed to recover various valuable end products, while reducing the environmental impact of the waste. Scandium is one of the valuable elements in bauxite residues. It is possible to extract and enrich scandium from red mud by leaching and solvent extraction. Scandium can then be recovered from the pregnant strip liquor by crystallization. Different crystallization techniques can be used to generate the supersaturation required for scandium to crystallize out as a salt. In the present study, the crystallization of an ammonium scandium fluoride phase by cooling and antisolvent crystallization techniques is presented. Cooling crystallization gave a low yield of ammonium scandium hexafluoride, (NH 4) 3 ScF 6 , below 50% at the lowest temperature of 1 °C investigated. Antisolvent crystallization using ethanol gave almost complete recovery with precipitation efficiency greater than 98% for an ethanol-to-strip liquor volumetric ratio of 0.8. Solubility data of (NH 4) 3 ScF 6 under different temperatures and in different ethanol-strip liquor mixtures is herein presented. The product obtained by antisolvent crystallization had very minute crystals (< 2 µm) due to the high supersaturation generated upon adding ethanol to the strip liquor, while it was easier to obtain larger crystals by cooling crystallization. Fe and Ti impurities were detected in the solid product, and an insight into the mechanism of impurity uptake is discussed.

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“…Such highly polar surfaces are expected to strongly interact with water molecules16171819. In this light, the recently reported intrinsic hydrophobicity11 is very surprising (Fig.…”

mentioning

confidence: 95%

Surface chemistry of rare-earth oxide surfaces at ambient conditions: reactions with water and hydrocarbons

Külah

Marot

Steiner

et al. 2017

Sci Rep

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Rare-earth (RE) oxide surfaces are of significant importance for catalysis and were recently reported to possess intrinsic hydrophobicity. The surface chemistry of these oxides in the low temperature regime, however, remains to a large extent unexplored. The reactions occurring at RE surfaces at room temperature (RT) in real air environment, in particular, in presence of polycyclic aromatic hydrocarbons (PAHs), were not addressed until now. Discovering these reactions would shed light onto intermediate steps occurring in automotive exhaust catalysts before reaching the final high operational temperature and full conversion of organics. Here we first address physical properties of the RE oxide, nitride and fluoride surfaces modified by exposure to ambient air and then we report a room temperature reaction between PAH and RE oxide surfaces, exemplified by tetracene (C18H12) on a Gd2O3. Our study evidences a novel effect – oxidation of higher hydrocarbons at significantly lower temperatures (~300 K) than previously reported (>500 K). The evolution of the surface chemical composition of RE compounds in ambient air is investigated and correlated with the surface wetting. Our surprising results reveal the complex behavior of RE surfaces and motivate follow-up studies of reactions between PAH and catalytic surfaces at the single molecule level.

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IUPAC-NIST Solubility Data Series. 100. Rare Earth Metal Fluorides in Water and Aqueous Systems. Part 1. Scandium Group (Sc, Y, La)

Cited by 26 publications

References 40 publications

Scandium Recovery from an Ammonium Fluoride Strip Liquor by Anti-Solvent Crystallization

Scandium Recovery from an Ammonium Fluoride Strip Liquor by Anti-Solvent Crystallization

Recovery of Scandium by Crystallization Techniques

Surface chemistry of rare-earth oxide surfaces at ambient conditions: reactions with water and hydrocarbons

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