Layer-by-layer membrane modification allows scandium recovery by nanofiltration
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07/2019
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01A - Journal article
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Environmental Science. Water, Research & Technology
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Pages / Duration
1683-1688
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Royal Society of Chemistry
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Abstract
Aluminium scandium (Sc) alloys are stronger, more corrosion resistant and more heat tolerant than classical
aluminium alloys and allow for 3D printing. In particular, the aerospace industry benefits from better fuel
efficiency due to lighter materials as well as the advantages of additive manufacturing. However, Sc is currently
not available in sufficient quantities and has recently been identified as a raw material critical to the
economy. Due to the recentness of the demand, technologies for recovery of Sc from secondary sources
are in their infancy. In this study, Sc recovery from titanium dioxide pigment production waste by nanofiltration
was investigated. Custom-made layer-by-layer (LbL) modified membranes were optimized with
regards to their elemental retention (i.e., selectivity towards Sc) as well as their acid resistance. In model solutions,
the optimized membrane retained up to 64% ± 4% Sc, removing the major impurity, iron (Fe), efficiently
(12% ± 7% retention) while achieving high flux [32 L m−2 h−1] at a low transmembrane pressure of 5
bar. Acid resistance was shown down to a pH of 0.1, which could be even further increased (up to ≤3 M
HCl) by adding more bi-layers and changing the coating conditions. In real wastes, the optimized LbL
membrane showed higher Sc retention (60% vs. 50%) compared to a commercial acid resistant membrane,
while achieving considerably higher fluxes [27 L m−2 h−1 versus 1 L m−2 h−1, respectively at 5 bar]. It was
possible to operate filtration at low transmembrane pressure with up to 70% permeate recovery and flux
that was still high [∼10 L m−2 h−1]. In a nutshell, titanium dioxide pigment wastes contained sufficient
amounts to satisfy the growing demand for Sc and can be exploited to their full extent by LbL nanofiltration
due to the proven advantages of acid stability, Sc retention and selectivity and high achievable fluxes at
low pressures.
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ISBN
ISSN
2053-1419
2053-1400
2053-1400
Language
English
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Yes
Strategic action fields FHNW
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Published
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Peer review of the complete publication
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Citation
Remmen, K., Lenz, M., Hedwig, S., & Wintgens, T. (2019). Layer-by-layer membrane modification allows scandium recovery by nanofiltration. Environmental Science. Water, Research & Technology, 1683–1688. https://doi.org/10.1039/C9EW00509A