Red mud as secondary source for critical raw materials – Extraction study
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2017
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01A - Journal article
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Journal of Chemical Technology & Biotechnology
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Volume
92
Issue / Number
11
Pages / Duration
2835–2844
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Wiley
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Abstract
Red mud is a by-product of alumina extraction from bauxite by the Bayer process produced in the billion tons scale worldwide. Red muds, or more generally bauxite residues, are regarded as waste, but may potentially be valuable sources of critical raw materials (CRM). In the present study both conventional extracting agents (mineral acids) and small molecular weight complexing agents (organic acids) were evaluated regarding their efficiency to extract CRM such as rare earth elements (REEs) from red mud. On a molar base, highest extraction efficiencies for REEs were achieved using HCl compared with the other acids investigated. Consequently, an experimental design approach was used to determine optimal conditions for CRM extraction using HCl. Instead of maximizing the extraction of a number of selected metals, the maximum economic potential as the sum of all metals (total metal extracted × economic value of the respective metal) was chosen as the application relevant response variable. Four explanatory variables (i.e. HCl concentration, contact time, temperature and slurry concentration) were used.
RESULTS
Optimal conditions maximizing the economic potential were predicted for 5.98 mol L−1 HCl, 21 h contact time, 50°C, and 56.7 g L−1 slurry concentration. Indeed, experimentally determined economic potential corresponded well (71% of predicted) with the predictions, allowing a maximum recovery of 297.6 US $ t−1.
CONCLUSION
Though the studied red muds were relatively low in CRM concentrations, the systematic approach developed here allows straightforward transfer to other red muds, harnessing the potential of the latter as important secondary source for CRM. © 2017 Society of Chemical Industry
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1097-4660
0268-2575
0142-0356
1935-181X
0268-2575
0142-0356
1935-181X
Language
English
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Yes
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Published
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Citation
Ujaczki, E., Zimmermann, Y., Molnar, M., Feigl, V., Lenz, M., & Gasser, C. A. (2017). Red mud as secondary source for critical raw materials – Extraction study. Journal of Chemical Technology & Biotechnology, 92(11), 2835–2844. https://doi.org/10.1002/jctb.5300