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Process Design Aspects for Scandium-Selective Leaching of Bauxite Residue with Sulfuric Acid

School of Chemical Engineering (Chem. Eng.), National Technical University of Athens (NTUA), 9 Iroon Polytechniou St., 15780 Athens, Greece
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This paper is the written, extended and updated version of the oral presentation entitled as “Design Aspects of a Selective Leaching Process for Scandium Recovery from Bauxite Residue”, in the ERES 2017 Conference (European Rare Earth Resources 2017), which was held in Santorini, Greece, 28–31 May 2017. Abstract and Presentation are available online at: http://eres2017.eresconference.eu/program/ (accessed on 23 January 2018); Hatzilyberis, K.; Lymperopoulou, T.; Tsakanika, L.-A.; Ochsenkuehn, K.; Georgiou, P.; Ochsenkuehn-Petropoulou, M. Design Aspects of a Selective Leaching Process for Scandium Recovery from Bauxite Residue. Book of Abstracts of ERES 2017 Conference (European Rare Earth Resources 2017), Santorini, Greece, 28–31 May 2017; Track 4: Rare Earth Elements from secondary resources, pp. 188–189.
Minerals 2018, 8(3), 79; https://doi.org/10.3390/min8030079
Received: 11 January 2018 / Revised: 13 February 2018 / Accepted: 21 February 2018 / Published: 25 February 2018
Aiming at the industrial scale development of a Scandium (Sc)-selective leaching process of Bauxite Residue (BR), a set of process design aspects has been investigated. The interpretation of experimental data for Sc leaching yield, with sulfuric acid as the leaching solvent, has shown significant impact from acid feed concentration, mixing time, liquid to solids ratio (L/S), and number of cycles of leachate re-usage onto fresh BR. The thin film diffusion model, as the fundamental theory for leaching, either with constant particle size for selective leaching, or with shrinking particle size for less- or non-selective leaching, interprets the relevant experimental data. In both cases, a concept for an unyielding core supplements the basic model. Especially for the selective leaching mild conditions, the simplest model version agrees with the experiments, since both prove 1st order kinetics, while for extreme conditions, a combined conversion rate model with diffusion and chemical reaction inside particles is proposed. The maximization of Sc recovery per unit of consumed solvent emerged as highly critical for the process economics. View Full-Text
Keywords: Scandium; REEs; bauxite residue; selective leaching; process design aspects; thin film diffusion model; unyielding core; specific recovery Scandium; REEs; bauxite residue; selective leaching; process design aspects; thin film diffusion model; unyielding core; specific recovery
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Hatzilyberis, K.; Lymperopoulou, T.; Tsakanika, L.-A.; Ochsenkühn, K.-M.; Georgiou, P.; Defteraios, N.; Tsopelas, F.; Ochsenkühn-Petropoulou, M. Process Design Aspects for Scandium-Selective Leaching of Bauxite Residue with Sulfuric Acid. Minerals 2018, 8, 79.

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