【作者】 李焕利；

【导师】 李小明；

【作者基本信息】 湖南大学 ， 环境工程， 2009， 硕士

【摘要】 生物冶金是一种利用微生物从矿物中提取有价金属的经济方法,特别适用于处理贫矿、表外矿及废矿,并具有成本低、投入小、能耗低、环境污染小等突出优点。在生物冶金中,对高效浸矿菌种的选育和机理研究意义重大。彭小伟等已从电解锰废渣中筛选出一株锰抗性强的霉菌A5,并对其进行了初步鉴定。在本文研究中,通过扩增26S rDNA D1/D2区序列,A5菌进一步鉴定为Fusarium属的一个种。为了研究其在电解锰废渣浸出中的作用,从锰渣及Fusarium sp.的特性出发,通过摇瓶试验对其浸锰条件进行了优化,同时考察了Fusarium sp.浸取前后锰渣中金属锰的形态变化,并对其浸锰能力进行了研究,初步探讨了Fusarium sp.的浸锰机理。从电解锰废渣土壤中筛选分离到一株锰抗性强的霉菌A5,已对其形态特征进行了初步研究。其菌丝细长,菌落疏松,菌落表面有绿、青、黑、橙不同颜色,培养基正反两面颜色有一定差异。基于26S rDNA,测序结果表明此菌属于Fusarium属的一个种。利用Fusarium sp.进行锰渣摇瓶浸出试验,试验发现,矿浆浓度为10%时锰浸出率最高,当矿浆浓度大于10%时,锰浸出率有所下降;锰浸出率随时间的增加而提高,30h时达到最大;加大接种量,对锰浸出率影响不大。Fe2+和Fe3+的加入能够提高锰浸出率。采用优化的BCR（European Community Bureau of Reference）连续萃取方案对Fusarium sp.浸取前后的金属锰进行了形态分析,研究了其锰浸出率和浸取前后锰的形态变化特征。同时考察了3种萃取剂EDTA、HNO₃和CaCl₂对锰的萃取效率及萃取后金属锰的形态变化,发现Fusarium sp.对锰的浸取能力较显著,3天后锰浸出率达56.5%,有利于从锰渣中回收金属锰。3种萃取剂对锰的浸取效果为EDTA>HNO₃>CaCl₂,平均萃取效率依次为50.0%,28.8%和21.2%。浸取前后,酸溶解态锰所占比例变化较显著,酸溶解态锰是比较容易浸取的形态。浸取过程中真菌代谢产生的生物酸是最重要的浸取剂。真菌浸矿的过程,不仅仅是其代谢产生生物酸参与的化学反应,微生物本身也起到了重要的作用。通过考察不同浓度硝酸、柠檬酸和草酸（0.1M和0.5M）的浸锰能力及Fusarium sp.浸锰过程中培养液pH的变化,对Fusarium sp.的浸锰机理进行了初步研究。同时对浸取前后的Fusarium sp.进行了扫描电镜,结果显示,Fusarium sp.代谢过程产生生物酸并参与了反应, Fusarium sp.本身在锰浸出过程中也起到了一定的吸附作用。更多还原

【Abstract】 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.更多还原