[Study on the bioleaching mechanism of manganse (II) from manganese-electrolytic residue by manganese-resistant strain Fusarium sp].

The manganse bioleaching mechanism by a manganese-resistant strain Fusarium sp. was investigated, through analyzing the bioleaching rate and manganese-electrolytic residue characterizations with the presence of Fusarium sp. and with the addition of organic acids. Special attention was paid to explore the relationship among the manganese's leaching rate, pH, and organic acid concentration during Fusarium sp. bioleaching process. The research results showed that, with the addition of Fusarium sp., some looser and more porous manganese-electrolytic residues could be obtained. And after 47 hours, the leaching rate reached to 84% which was 2.30 times higher than that leached by individual organic acid even after 130 hours; the leaching rate of manganese and the concentrations of organic acids increased at the initial stage and then decreased, while pH was the reversed. Additionally, the concentration of Succinic acid and L-Malic acid reached their crest value (11.12 g/L and 10.23 g/L) at 57 and 62 hours respectively. Yet the pH reached the lowest (4.09) at 29 h, which implied that, Fusarium sp. and organic acid produced played an important role in the leaching of manganese, leading to a high-efficiency and time-saving process. However, due to the high density of manganese-electrolytic residue and the concurrence of the produce and consumption of organic acid together with the adsorption and complexation, the relationship among the extraction rate for manganese ion, pH, and the concentration of organic acid produced could not be described by simple linear correlation and the leaching rate decreased significantly in the later stage.