Efficient dealkalization of red mud and recovery of valuable metals by a sulfur-oxidizing bacterium

Duo-rui Zhang, Hong-rui Chen, Jin-lan Xia, Zhen-yuan Nie, Rui-yong Zhang, Eva Pakostova

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    Red mud (RM) is a highly alkaline polymetallic waste generated via the Bayer process during alumina production. It contains metals that are critical for a sustainable development of modern society. Due to a shortage of global resources of many metals, efficient large-scale processing of RM has been receiving increasing attention from both researchers and industry. This study investigated
    the solubilization of metals from RM, together with RM dealkalization, via sulfur (S0) oxidation catalyzed by the moderately
    thermophilic bacterium Sulfobacillus thermosulfidooxidans. Optimization of the bioleaching process was conducted in shake flasks and 5-L bioreactors, with varying S0:RM mass ratios and aeration rates. The ICP analysis was used to monitor the concentrations of dissolved elements from RM, and solid residues were analyzed for surface morphology, phase composition, and Na distribution using the SEM, XRD, and STXM techniques respectively. The results show that highest metal recoveries (89% of Al, 84% of Ce, and 91% of Y) were achieved with the S0:RM mass ratio of 2:1 and aeration rate of 1 L/min. Additionally, effective dealkalization of RM was
    achieved under the above conditions, based on the high rates (> 95%) of Na, K, and Ca dissolution. This study proves the feasibility
    of using bacterially catalyzed S0 oxidation to simultaneously dealkalize RM and efficiently extract valuable metals from the
    amassing industrial waste.
    Original languageEnglish
    Article number973568
    Number of pages15
    JournalFrontiers in Microbiology
    Early online date29 Aug 2022
    Publication statusPublished - 29 Aug 2022

    Bibliographical note

    © 2022 Zhang, Chen, Xia, Nie, Zhang and Pakostova. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms


    • Red mud
    • Bioleaching
    • Dealkalization
    • Metal recovery
    • Sulfur bio-oxidation


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