Abstract—In the present study, bioleaching of vanadium and nickel from an oil-fired ash sample was conducted using Aspergillus niger fungus. Oil-fired ash is a major by-product of thermal power plants which is considered as a secondary source for V and Ni recovery. The experiments were carried out using spent-medium bioleaching method in both Shake flasks and also bubble column bioreactor, in order to compare them together. In Shake flask experiments the fungus was cultured for 14 days, where the maximum production of organic acids was observed, while in bubble column bioreactor experiments a 7 days fermentation period was applied. Measurement of produced organic acids during fermentation period indicated that the main excreted metabolites by Aspergillus niger in Shake flasks were different with that of bioreactor since the fermentation conditions in these two various scales differed significantly. In both of the scales the concentrations of citric, oxalic, gluconic and malic acids were measured and it was revealed that in Shake flask experiments citric acid, and in bubble column bioreactor oxalic acid was the major lixiviant, while the production of gluconic acid was similarly lower. In Shake flask and during 14 days of fermentation of Aspergillus niger, 8080 ppm citric acid and 1170 ppm oxalic acid was produced, while in bubble column bioreactor and over 7 days of fungal growth, 17185 ppm oxalic acid and 1040 ppm citric acid was secreted. For conducting the leaching tests using the spent-media obtained from both of fermentation experiments, a 60 °C leaching temperature, 7 days leaching duration and solid to liquid ratio of 3% (w/v) was selected. Using Shake flask experiments spent-media, maximum V and Ni recovery yields were 97% and 50% respectively, whereas using bubble column bioreactor spent-medium, 100% of V and 33% of Ni was recovered.
Index Terms—
Aspergillus niger, Bubble column bioreactor, Oil-fired ash, Spent-medium bioleaching.
The authors are with Biotechnology Group, Chemical Engineering Department, Tarbiat Modares University, Tehran, Iran (corresponding author: Seyyed Mohammad Mousavi; phone: +98-21-82884917; fax: +98-21-82884931; e-mail: payam.rasoulnia@gmail.com, mousavi_m@modares.ac.ir).
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Cite: Payam Rasoulnia and Seyyed Mohammad Mousavi, "Bioleaching of Precious Metals from an Oil-Fired Ash Using Organic Acids Produced by Aspergillus Nigerin Shake Flasks and Bioreactor," International Journal of Chemical Engineering and Applications vol. 7, no. 6, pp. 365-368, 2016.
