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Koen Binnemans - One of the best experts on this subject based on the ideXlab platform.
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Recovery of Scandium from sulfation-roasted leachates of bauxite residue by solvent extraction with the ionic liquid betainium bis(trifluoromethylsulfonyl)imide
Separation and Purification Technology, 2017Co-Authors: Bieke Onghena, Chenna Rao Borra, Tom Van Gerven, Koen BinnemansAbstract:Bauxite residue (red mud) is a waste product of the alumina refining in the Bayer process and contains significant concentrations of critical metals, including Scandium. Greek bauxite residue contains exploitable levels of Scandium and is thus considered a suitable source for its production. A process was developed to recover Scandium from Greek bauxite residue using a combination of sulfation-roasting-leaching and solvent extraction with the hydrophobic ionic liquid betainium bis(trifluoromethylsulfonyl)imide, [Hbet][Tf2N]. Sulfation-roasting-leaching was the preferred leaching technique to dissolve Scandium from bauxite residue because of the low acid consumption, good selectivity towards Scandium and low co-dissolution of the major elements. The Scandium concentration in the leachate was increased by applying multistage leaching, during which the obtained leachate is contacted multiple times with freshly roasted material. In a next step, Scandium was selectively extracted from the obtained leachate with [Hbet][Tf2N]. To improve the separation between Scandium and iron, Fe(III) was reduced to Fe(II) by addition of ascorbic acid to the sulfate leachate prior to extraction. The phase ratio and pH of the extraction were optimized to achieve high extraction and concentration of Scandium in the ionic liquid phase. Co-extracted metal ions were scrubbed from the loaded ionic liquid phase by HCl and the purified Scandium was removed by stripping with H2SO4. Scandium was recovered from the strip solution by precipitation together with sodium. Finally, the entire process was performed on lab scale as a proof-of-principle.
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recovery of Scandium from leachates of greek bauxite residue by adsorption on functionalized chitosan silica hybrid materials
Green Chemistry, 2016Co-Authors: Joris Roosen, Chenna Rao Borra, Stijn Van Roosendael, Tom Van Gerven, Steven Mullens, Koen BinnemansAbstract:Bauxite residue (red mud) is a waste residue that results from the production of alumina by the Bayer process. Since it has no large-scale industrial application, it is stockpiled in large reservoirs. Nevertheless, it should be considered as a valuable secondary resource as it contains relatively large concentrations of critical metals like the rare earths, Scandium being the most important one. In this work, we investigated the recovery of Scandium from real leachates of Greek bauxite residue. In the separation of Scandium from the other elements, the biggest challenge arose from the chemical similarities between Scandium(III) and iron(III). This hampers high selectivity for Scandium, especially because iron, as one of the major elements in bauxite residue, is present in much higher concentrations than Scandium. In order to achieve selectivity for Scandium, chitosan–silica particles were functionalized with the chelating ligands diethylenetriamine pentaacetic acid (DTPA) and ethyleneglycol tetraacetic acid (EGTA). Both organic ligands were chosen because of the high stability constants between Scandium(III) and the corresponding functional groups. The adsorption kinetics and the influence of pH on hydrolysis and adsorption were investigated batchwise from single-element solutions of Scandium(III) and iron(III). In binary solutions of Scandium(III) and iron(III), it was observed that only EGTA-functionalized chitosan–silica appeared to be highly selective for Scandium(III) over iron(III). EGTA–chitosan–silica shows a much higher selectivity over state-of-the-art adsorbents for the separation of Scandium(III) from iron(III). The latter material was therefore used as a resin material for column chromatography in order to effectively separate Scandium from bauxite residue. Full separation was achieved by eluting the column with HNO3 solution at pH 0.50; at this pH all other elements had already eluted.
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recovery of Scandium iii from aqueous solutions by solvent extraction with the functionalized ionic liquid betainium bis trifluoromethylsulfonyl imide
Industrial & Engineering Chemistry Research, 2015Co-Authors: Bieke Onghena, Koen BinnemansAbstract:The ionic liquid betainium bis(trifluoromethylsulfonyl)imide [Hbet][Tf2N] was used for the extraction of Scandium from aqueous solutions. The influence of several extraction parameters on the extraction efficiency was investigated, including the initial metal concentration, phase ratio, and pH. The extraction kinetics was examined, and a comparison was made between conventional liquid–liquid extraction and homogeneous liquid–liquid extraction (HLLE). The stoichiometry of the extracted Scandium complex was determined with slope analysis. Scandium(III) is extracted as a complex with zwitterionic betaine in a 1:3 stoichiometry, with three bis(trifluoromethylsulfonyl)imide counterions. Upon extraction of Scandium(III), proton exchange occurs and three protons are transferred to the aqueous phase. Scandium is an important minor element present in bauxite residue (red mud), the waste product that results from the industrial production of alumina by the Bayer process. To evaluate the suitability of [Hbet][Tf2N] ...
Bieke Onghena - One of the best experts on this subject based on the ideXlab platform.
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Recovery of Scandium from sulfation-roasted leachates of bauxite residue by solvent extraction with the ionic liquid betainium bis(trifluoromethylsulfonyl)imide
Separation and Purification Technology, 2017Co-Authors: Bieke Onghena, Chenna Rao Borra, Tom Van Gerven, Koen BinnemansAbstract:Bauxite residue (red mud) is a waste product of the alumina refining in the Bayer process and contains significant concentrations of critical metals, including Scandium. Greek bauxite residue contains exploitable levels of Scandium and is thus considered a suitable source for its production. A process was developed to recover Scandium from Greek bauxite residue using a combination of sulfation-roasting-leaching and solvent extraction with the hydrophobic ionic liquid betainium bis(trifluoromethylsulfonyl)imide, [Hbet][Tf2N]. Sulfation-roasting-leaching was the preferred leaching technique to dissolve Scandium from bauxite residue because of the low acid consumption, good selectivity towards Scandium and low co-dissolution of the major elements. The Scandium concentration in the leachate was increased by applying multistage leaching, during which the obtained leachate is contacted multiple times with freshly roasted material. In a next step, Scandium was selectively extracted from the obtained leachate with [Hbet][Tf2N]. To improve the separation between Scandium and iron, Fe(III) was reduced to Fe(II) by addition of ascorbic acid to the sulfate leachate prior to extraction. The phase ratio and pH of the extraction were optimized to achieve high extraction and concentration of Scandium in the ionic liquid phase. Co-extracted metal ions were scrubbed from the loaded ionic liquid phase by HCl and the purified Scandium was removed by stripping with H2SO4. Scandium was recovered from the strip solution by precipitation together with sodium. Finally, the entire process was performed on lab scale as a proof-of-principle.
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recovery of Scandium iii from aqueous solutions by solvent extraction with the functionalized ionic liquid betainium bis trifluoromethylsulfonyl imide
Industrial & Engineering Chemistry Research, 2015Co-Authors: Bieke Onghena, Koen BinnemansAbstract:The ionic liquid betainium bis(trifluoromethylsulfonyl)imide [Hbet][Tf2N] was used for the extraction of Scandium from aqueous solutions. The influence of several extraction parameters on the extraction efficiency was investigated, including the initial metal concentration, phase ratio, and pH. The extraction kinetics was examined, and a comparison was made between conventional liquid–liquid extraction and homogeneous liquid–liquid extraction (HLLE). The stoichiometry of the extracted Scandium complex was determined with slope analysis. Scandium(III) is extracted as a complex with zwitterionic betaine in a 1:3 stoichiometry, with three bis(trifluoromethylsulfonyl)imide counterions. Upon extraction of Scandium(III), proton exchange occurs and three protons are transferred to the aqueous phase. Scandium is an important minor element present in bauxite residue (red mud), the waste product that results from the industrial production of alumina by the Bayer process. To evaluate the suitability of [Hbet][Tf2N] ...
Magnus Sandström - One of the best experts on this subject based on the ideXlab platform.
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the hydration of the Scandium iii ion in aqueous solution and crystalline hydrates studied by xafs spectroscopy large angle x ray scattering and crystallography
Dalton Transactions, 2006Co-Authors: Patric Lindqvistreis, Ingmar Persson, Magnus SandströmAbstract:The structures of the hydrated Scandium(III) ion and of the hydrated dimeric hydrolysis complex, [Sc2(µ-OH)2]4+, in acidic aqueous solutions have been characterized by X-ray absorption fine structure (XAFS) and large-angle X-ray scattering (LAXS) methods. Comparisons with crystalline reference compounds containing hydrated Scandium(III) ions in well characterized six-, seven- and eight-coordinated polyhedra have been used to evaluate the coordination numbers and configurations in aqueous solution. In strongly acidic aqueous solution the structure of the hydrated Scandium(III) ion is found to be similar to that of the eight-coordinated Scandium(III) ion with distorted bicapped trigonal prismatic coordinating geometry in the crystalline [Sc(H2O)8.0](CF3SO3)3 compound. The EXAFS data reveal for the solution, as for the solid, a mean Sc–O bond distance of 2.17(1) A to six strongly bound prism water molecules, 2.32(4) A to one capping position, with possibly another capping position at about 2.5 A. The LAXS study supports this structural model and shows furthermore a second hydration sphere with ∼12 water molecules at a mean Sc⋯OII distance of 4.27(3) A. In less acidic concentrated Scandium(III) aqueous solutions, the dimeric hydrolysis product, [Sc2(µ-OH)2(H2O)10]4+, is the predominating species with seven-coordinated Scandium(III) ions in a double hydroxo bridge and five terminal water molecules at a mean Sc–O bond distance of 2.145 A. Hexahydrated Scandium(III) ions are found in the crystal structure of the double salt [Sc(H2O)6][Sc(CH3SO3)6], which crystallizes in the trigonal space group R with Z = 6 and the unit cell dimensions a = 14.019(2) and c = 25.3805(5) A. The Sc–O distances in the two crystallographically unique, but nearly identical, [Sc(H2O)6]3+ entities (both with imposed crystallographic symmetry) are 2.085(6) and 2.086(5) A, while the mean Sc–O distance in the near octahedral [Sc(OSO2CH3)6]3− entities (with three-fold symmetry) is 2.078 A.
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Vibrational spectroscopic force field studies of dimethyl sulfoxide and hexakis(dimethyl sulfoxide)Scandium(III) iodide, and crystal and solution structure of the hexakis(dimethyl sulfoxide)Scandium(III) ion
Dalton Transactions, 2004Co-Authors: Mikhail Yu. Skripkin, Patric Lindqvist-reis, János Mink, Ingmar Persson, Alireza Abbasi, Magnus SandströmAbstract:Hexakis(dimethyl sulfoxide)Scandium(III) iodide, [Sc(OS(CH3)2)6]I3 contains centrosymmetric hexasolvated Scandium(III) ions with an Sc–O bond distance of 2.069(3) A. EXAFS spectra yield a mean Sc–O bond distance of 2.09(1) A for solvated Scandium(III) ions in dimethyl sulfoxide solution, consistent with six-coordination. Raman and infrared absorption spectra have been recorded, also of the deuterated compound, and analysed by means of normal coordinate methods, together with spectra of dimethyl sulfoxide. The effects on the vibrational spectra of the weak intermolecular C–H⋯O interactions and of the dipole–dipole interactions in liquid dimethyl sulfoxide have been evaluated, in particular for the S–O stretching mode. The strong Raman band at 1043.6 cm−1 and the intense IR absorption at 1062.6 cm−1 have been assigned as the S–O stretching frequencies of the dominating species in liquid dimethyl sulfoxide, evaluated as centrosymmetric dimers with antiparallel polar S–O groups. The shifts of vibrational frequencies and force constants for coordinated dimethyl sulfoxide ligands in hexasolvated trivalent metal ion complexes are discussed. Hexasolvated Scandium(III) ions are found in dimethyl sulfoxide solution and in [Sc(OSMe2)6]I3. The iodide ion–dipole attraction shifts the methyl group C–H stretching frequency for (S–)C–H⋯I− more than for the intermolecular (S–)C–H⋯O interactions in liquid dimethyl sulfoxide.
Georges Calas - One of the best experts on this subject based on the ideXlab platform.
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Australian Laterites Reveal Mechanisms Governing Scandium Dynamics in the Critical Zone
Geochimica et Cosmochimica Acta, 2019Co-Authors: Mathieu Chassé, William L. Griffin, Suzanne Y. O'reilly, Georges CalasAbstract:Abstract Scandium is often considered as immobile during chemical weathering, based on its low solubility. In contrast to other conservative ( i.e. relatively immobile) elements incorporated into accessory minerals resistant to weathering ( e.g. zirconium, thorium or niobium), the scarcity of Scandium minerals indicates that the processes accounting for Scandium’s immobilisation are distinctive. However, the evolution of Scandium speciation during weathering is unknown, limiting the understanding of the processes controlling its dynamics in the critical zone. Exceptional Scandium concentrations in east Australian laterites provide the possibility of unravelling these mechanisms. We follow Scandium speciation through thick lateritic profiles ( > 30 m) using a multiscale mineralogical and spectroscopic approach involving electron microprobe, laser-ablation–inductively coupled plasma mass spectrometry, selective leaching and X-ray absorption near-edge structure spectroscopy, complemented by mass-transfer calculations. We show that the initial reservoir of Scandium contained in the parent rock is preserved under reducing conditions occurring in the lowest horizons of the profiles. The dissolution of Scandium-bearing clinopyroxene generates smectitic clays that immobilise and concentrate Scandium. It is subsequently trapped in the lateritic duricrust by goethite. Scandium mobilisation appears in this horizon and increases upward as a result of the dissolution of goethite, possibly assisted by dissolved organic matter, and the precipitation of hematite. Molecular-scale analyses demonstrate that changes in speciation govern Scandium dynamics, with substitution in smectitic clays and adsorption on iron oxyhydroxides playing a crucial role in Scandium immobility in the saprolite and lower lateritic duricrust. The higher affinity of Scandium for goethite relative to hematite drives Scandium mobilisation in the upper lateritic duricrust, leading to its concentration downward in the lower lateritic duricrust. These successive mechanisms illustrate how the unique complexity of the critical zone leads to Scandium concentrations that may form new types of world-class Scandium deposits. Comparison with conservative elements and with rare-earth elements, expected to have similar geochemical properties, emphasizes the unique behaviour of Scandium in the critical zone. While Scandium remains immobile during the early stages of weathering, intense and long-term alteration processes, observed in lateritic contexts, lead to Scandium mobilisation. This study highlights the dependence of Scandium mobility on weathering conditions.
Chenna Rao Borra - One of the best experts on this subject based on the ideXlab platform.
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Recovery of Scandium from sulfation-roasted leachates of bauxite residue by solvent extraction with the ionic liquid betainium bis(trifluoromethylsulfonyl)imide
Separation and Purification Technology, 2017Co-Authors: Bieke Onghena, Chenna Rao Borra, Tom Van Gerven, Koen BinnemansAbstract:Bauxite residue (red mud) is a waste product of the alumina refining in the Bayer process and contains significant concentrations of critical metals, including Scandium. Greek bauxite residue contains exploitable levels of Scandium and is thus considered a suitable source for its production. A process was developed to recover Scandium from Greek bauxite residue using a combination of sulfation-roasting-leaching and solvent extraction with the hydrophobic ionic liquid betainium bis(trifluoromethylsulfonyl)imide, [Hbet][Tf2N]. Sulfation-roasting-leaching was the preferred leaching technique to dissolve Scandium from bauxite residue because of the low acid consumption, good selectivity towards Scandium and low co-dissolution of the major elements. The Scandium concentration in the leachate was increased by applying multistage leaching, during which the obtained leachate is contacted multiple times with freshly roasted material. In a next step, Scandium was selectively extracted from the obtained leachate with [Hbet][Tf2N]. To improve the separation between Scandium and iron, Fe(III) was reduced to Fe(II) by addition of ascorbic acid to the sulfate leachate prior to extraction. The phase ratio and pH of the extraction were optimized to achieve high extraction and concentration of Scandium in the ionic liquid phase. Co-extracted metal ions were scrubbed from the loaded ionic liquid phase by HCl and the purified Scandium was removed by stripping with H2SO4. Scandium was recovered from the strip solution by precipitation together with sodium. Finally, the entire process was performed on lab scale as a proof-of-principle.
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recovery of Scandium from leachates of greek bauxite residue by adsorption on functionalized chitosan silica hybrid materials
Green Chemistry, 2016Co-Authors: Joris Roosen, Chenna Rao Borra, Stijn Van Roosendael, Tom Van Gerven, Steven Mullens, Koen BinnemansAbstract:Bauxite residue (red mud) is a waste residue that results from the production of alumina by the Bayer process. Since it has no large-scale industrial application, it is stockpiled in large reservoirs. Nevertheless, it should be considered as a valuable secondary resource as it contains relatively large concentrations of critical metals like the rare earths, Scandium being the most important one. In this work, we investigated the recovery of Scandium from real leachates of Greek bauxite residue. In the separation of Scandium from the other elements, the biggest challenge arose from the chemical similarities between Scandium(III) and iron(III). This hampers high selectivity for Scandium, especially because iron, as one of the major elements in bauxite residue, is present in much higher concentrations than Scandium. In order to achieve selectivity for Scandium, chitosan–silica particles were functionalized with the chelating ligands diethylenetriamine pentaacetic acid (DTPA) and ethyleneglycol tetraacetic acid (EGTA). Both organic ligands were chosen because of the high stability constants between Scandium(III) and the corresponding functional groups. The adsorption kinetics and the influence of pH on hydrolysis and adsorption were investigated batchwise from single-element solutions of Scandium(III) and iron(III). In binary solutions of Scandium(III) and iron(III), it was observed that only EGTA-functionalized chitosan–silica appeared to be highly selective for Scandium(III) over iron(III). EGTA–chitosan–silica shows a much higher selectivity over state-of-the-art adsorbents for the separation of Scandium(III) from iron(III). The latter material was therefore used as a resin material for column chromatography in order to effectively separate Scandium from bauxite residue. Full separation was achieved by eluting the column with HNO3 solution at pH 0.50; at this pH all other elements had already eluted.
