Characterization Of Fusarium Sp. From Electrolytic Manganese Residue And The Study On Its Leaching Ability Of Manganese

Bioleaching is an economical method for the recovery of metals from minerals, especially from low grade ores, overburden and waste from current mining operations, which requires moderate capital investment with low operating cost. Furthermore, bioleaching is generally more environmentally friendly than conventional metal recovery processes. Therefore, it is of great significance for screening efficient strains and studying the mechanisms of bioleaching. The strain A5, which has strong resistance to manganese, has been isolated from electrolytic manganese residue and preliminarily identified by Peng Xiaowei. In this study, the strain A5 was further identified as Fusarium sp. through the amplification of 26S rDNA D1/D2 sequence. To understand the role Fusarium sp. plays in manganese bioleaching, according to the characteristics of Fusarium sp. and manganese residue, we focused on the optimized leaching conditions through shake-flask experiments and the redistribution of Mn before and after bioleaching and the leaching ability of Fusarium sp. and its effect on manganese dissolution from manganese residue.The modality of A5, which was slender hyphae, loose colonies, has been studied. It has different colors of green, blue, black, orange in the colony surface and the colors between the positive and negative sides of the medium have a certain difference. Based on 26S rDNA, sequencing results showed that the strain belonged to the genus Fusarium. The shake-flask leaching experiments of Fusarium sp. found that the manganese leaching rate reached the best at the pulp concentration of 10%; when the pulp concentration was higher than 10%, the leaching rate of manganese decreased; with time increasing, the leaching rate of manganese increased and reached the maximum at 30h; the amount of inoculation had little effect on the leaching rate of manganese. Fe²⁺ and Fe³⁺ can enhance the leaching rate.The redistribution of Mn was determined using the sequential extraction procedures of the optimized European Community Bureau of Reference (BCR) before and after leaching. Extractions were compared with chemical leaching, where EDTA, HNO₃ and CaCl₂ were used as extractants. Results indicated that Fusarium sp., whose leaching efficiency was 56.5% after three days, showed strong leaching capacity for Mn, providing a scientific basis for manganese residue pollution treatment and resource utilization. The extractability of extractants for Mn was in the order EDTA > HNO₃ > CaCl₂ and the extractable efficiencies were 50.0%, 28.8% and 21.2% respectively. After leaching, the proportion of Mn in acid-extraction fraction varied considerably, showing that the acid-extraction fraction was proned to be leached.The bio-acids produced in fungal metabolism are the most important leaching agent. In the fungal bioleaching process, not just the bio-acids involve in the reactions, the microorganisms themselves also play an important role. In order to study the leaching mechanism of Fusarium sp., the leaching capabilities of different concentrations of nitric acid, citric acid and oxalic acid (0.1M and 0.5M) were investigated. The variation of pH of the culture medium was examined simultaneously and it was proved true that Fusarium sp. produced bio-acids which involved in the reactions. The results of the scanning electron microscope of Fusarium sp. before and after bioleaching showed that Fusarium sp. itself had played a certain amount of adsorption effect in the leaching process of manganese.