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Bioleaching of Egyptian Fly Ash Using Cladosporium cladosporioides

Heba A. Seddiek, Yousseria M. Shetaia, Khaled F. Mahamound, Ibrahim E. El-Aassy and Shimaa S. Hussien
Nuclear Materials Authority, P. O. Box 530, El Maadi, Cairo, Egypt
*(e-mail :; Telephone : +201229257655)
(Received : June 29, 2020; Accepted : August 17, 2020)


A large amount of fly ash is generated in Egyptian power plants as an industrial by-product which causes a lot of environmental problems due to the presence of hazardous heavy metals such as vanadium and nickel. These valuable metals can be recovered by an economically and environmentally acceptable bioleaching process. Bioleaching of fly ash was performed by the fungal isolate Cladosporium cladosporioides that achieved maximum bioleaching efficiency of vanadium and nickel using two-step method. Fly ash was involved into roasting process with different thermal pretreatments to convert vanadium compound into more soluble forms. The optimum conditions for bioleaching of vanadium and nickel were found to be 1% (w/v) sample concentration and incubation period 10 days. While initial pH was 6 and 8 for V and
Ni, respectively. Under these conditions, maximum bioleaching efficiencies were 65.4 and 74.6%, respectively for V and Ni. Organic acids were produced by C. cladosporioides, were estimated by HPLC in pure and optimum cultures. Malic acid was found to be the main produced organic acid.
Key words : Bioleaching, Cladosporium cladosporioides, fly ash, nickel, vanadium