Role of Aspergillus niger in recovery enhancement of valuable metals from produced red mud in Bayer process

• Published in: Bioresource technology 2016-10, Vol.218, p.991-998
• Main Authors: Vakilchap, F., Mousavi, S.M., Shojaosadati, S.A.
• Format: Article
• Language: English
• Subjects: Aspergillus niger; Bioleaching; Bioreactors - microbiology; Hazardous Waste; Industrial Waste; Metallurgy; Metals - isolation & purification; Organic acids; Red mud; Refuse Disposal - methods; Valuable metals
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2016.07.059

[Display omitted] •The role of Aspergillus niger on solubilization of metals in red mud was studied.•Organic acids secreted by the fungus were the main lixiviants in fungal leaching.•Recovery of metals in one-step, two-step and spent-medium bioleaching was compared.•The highest leaching efficiency of Al, Ti and Fe was obtained in the one-step process.•Bioleaching is an effective technique for environmental and economic purposes. Annual worldwide growth rate of red mud (RM) as a hazardous waste has caused serious environmental problems for its disposal in the mining and metallurgy industries. Accordingly, the aim of this study was to investigate biological leaching of RM and recovery of metals using organic acids exerted by Aspergillus niger. Experiments using A. niger were conducted in batch cultures with a pulp density of 2% (w/v) RM under one-step, two-step and spent-medium bioleaching. Based on HPLC results, the major lixiviant was the secretion of organic acids (citric, gluconic, oxalic and malic) by A. niger. Leaching efficiency of metals in the one-step process was the highest and the amounts of leached metals were 69.8%, 60% and 25.4% for Al, Ti and Fe, respectively. The fungal leaching technique demonstrated an adequate recovery of metals, with an efficient and cost-effective means and respect to a reuse of RM for economic and environmental purposes.