Environmentally sustainable and cost-effective bioleaching of aluminum from low-grade bauxite ore using marine-derived Aspergillus niger
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In this study, an economical and sustainable bio-hydrometallurgical route was evaluated for the recovery of aluminum from low-grade bauxite using the marine-derived fungus Aspergillus niger. Firstly, four different solid media were tested for high-yield spore production. Organic acid production capacity by A. niger was also evaluated in a medium supplemented with glucose or low-cost molasses as a carbon source using fungal spores or pellets as inoculum. The concentrations of the produced organic acids were determined by High-Performance Liquid Chromatography (HPLC). The results showed that oat-agar can be used as an inexpensive solid medium for greater fungal sporulation, while the liquid medium supplemented with molasses as a low-cost carbon source can be used for higher organic acids production. Among the conditions tested, A. niger spore inoculum showed the highest yield of the total produced organic acids (122.40 g L−1 or 81.6% (grams of sucrose used per grams of total acid) and also the highest (1.02 ± 0.02 g L−1 h−1) acids production rate using molasses as an inexpensive carbon source. This cultivation condition was selected for the bioleaching studies with low-grade bauxite. Among the three different bioleaching methods tested, the direct two-steps bioleaching process resulted in higher aluminum leaching (91.2%) compared to indirect (84.8%) and direct one-step (82.8%) bioleaching process. According to the results obtained using marine-derived A. niger under the established culture conditions, proved to be an eco-friendly and cost-effective way for aluminum recovery from low-grade bauxite ore and has the potential to be adopted on a pilot scale.
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Aluminum recovery, Aspergillus niger, Bioleaching, Low-grade bauxite, Molasses
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Hydrometallurgy, v. 195.
