Recovery of scandium(iii) from diluted aqueous solutions by a supported ionic liquid phase (SILP)

Abstract

The adsorption of scandium from diluted, acidic solutions by a supported ionic liquid phase (SILP) was investigated, as part of a process for recovery of scandium from bauxite residue (red mud). Both dry impregnation and covalent linking were studied for the SILP preparation. The SILP betainium sulfonyl(trifluoromethanesulfonylimide) poly(styrene-co-divinylbenzene) [Hbet-STFSI-PS-DVB] was prepared by covalent linking of the ionic liquid to the resin and this resulted in an adsorbent suitable for scandium recovery. For a chloride feed solution, the effects of pH, contact time, adsorption capacity, desorption, reusability of adsorbent and the influence of Fe(III), Al(III) and Ca(II) on the Sc(III) adsorption were studied. The adsorption of Sc(III) from nitrate and sulfate feed solution under optimal conditions was studied as well. The adsorption kinetics followed a pseudo-second order kinetic model. Equilibrium studies at room temperature showed that the experimental data could be well fitted by the Langmuir isotherm model. The stripping of Sc(III) from the loaded SILP was achieved with 1 M sulfuric acid. The SILP was stable and could be reused for seven adsorption/desorption cycles without significant losses in its adsorption efficiency for Sc(III). IntroductionScandium belongs to the group of rare-earth elements (REEs) and nds applications in aluminum alloys, halide lamps and fuel cells.1 However, it is an expensive metal with small global production volumes. Although scandium is relatively abundant in the Earth's crust (22 ppm), there are few scandium minerals and it rarely occurs in rich ore deposits. It is mainly recovered as by-product from the production of other metals (REEs, U, Ti, W, Al, Ni, Ta and Nb).2-4 Bauxite residue (red mud), the waste industrial product of the Bayer process for alumina production from bauxite ore, can contain up to 130 ppm of scandium and it is potentially a valuable scandium resource.5,6 Scandium can partially be recovered from bauxite residue by acid leaching. Typically, in this way many metal impurities go into the leachate as well and in concentrations much higher than that of scandium. 1,7,8 Liquid-liquid extraction is used for the recovery of Sc(III), 9 but it requires much higher initial concentrations of Sc(III) than the ones that can be found in the pregnant leach solutions.1 Nevertheless, for recovery of low concentrations of Sc(III) its enrichment with a selective adsorbent in high capacity ion exchange columns could be an efficient technique. Much of the research work on Sc(III) recovery by adsorption and extraction has been performed with resins, View Article OnlineView Journal | View Issue components can contaminate the aqueous effluents. 37 In the second class of SILPs there is no discrete IL phase in the structure of the solid support. Instead, the IL can be considered as a covalently anchored ligand. Covalent linking ensures that the IL will not be leached from the support. 32,40The objective of this work is to develop a stable SILP for the adsorption of Sc(III...

Effect of Aqueous Media on the Recovery of Scandium by Selective Precipitation

“…Zhang et al recovered 91% of Sc from bauxite residue leachates by inorganic metal(IV)-phosphate ion exchangers, although Fe(III) was found to be an interfering ion in this process [20]. In another study, a newly developed supported ionic liquid phase (SILP) achieved almost complete Sc extraction, while showing a decreased efficiency in the presence of Fe(III) [14]. In all of these hydrometallurgical operations, the co-extraction of Fe, Al, and Ti became a problem, and intensive purification was required to produce a high-quality product.…”

“…Previously, complete or partial recovery of Sc from bauxite residues was reported to be achieved mainly by solvent extraction, ion exchange, or the combination of these two techniques, as a result of its low concentration in the leachates [14][15][16][17][18][19][20]. Zhang et al recovered 91% of Sc from bauxite residue leachates by inorganic metal(IV)-phosphate ion exchangers, although Fe(III) was found to be an interfering ion in this process [20].…”

Quaternization of algal/PEI beads (a new sorbent): Characterization and application to scandium sorption from aqueous solutions

“…Different types of sorbents have been reported for the sorption of scandium from dilute solutions, including (a) biosorbents such as yeast [17], bacteria [18] or algae [19], carbon-based materials [20], resins [21][22][23][24]; impregnated resins [25][26][27]. Recently a new generation of materials has been designed using the interactions of alginate and polyethyleneimine (PEI) for manufacturing bead sorbents [28].…”

Using Life Cycle Thinking to Assess the Sustainability Benefits of Complex Valorization Pathways for Bauxite Residue

“…Following on from leaching, the dissolved metals must be selectively separated and recovered, most commonly in the form of oxides. In the REDMUD project, this is being undertaken using selective precipitation and solvent extraction [28,32], column separation [33], and supported ionic liquid phases (SILPs) [34,35].…”