【作者】 曹建兵；

【导师】 李小明； 欧阳玉祝；

【作者基本信息】 湖南大学 ， 环境科学与工程， 2011， 博士

【摘要】 随着电解锰产业的飞速发展,进入到环境中的电解锰废渣越来越多,由于电解锰废渣为酸浸渣,本身的pH值较低,同时废渣中还含有大量的金属离子,这些金属离子会随着雨水的淋溶以及本身的渗漏作用而进入到地表水以及地下水中,进入到地表水和地下水中的金属离子会随着食物链进入人体,从而对人体的健康造成了很大的威胁和危害,同时,电解锰废渣的露天堆积会对堆积场周围的土壤造成严重的生态破坏,改变土壤的结构,从而使土壤不利于农作物的生长。但是废渣中含有的一定量的有价金属可以通过一定的方式和方法加以回收和利用,这些回收利用的方法包括物理浸出、化学浸出以及两种作用相结合的浸出,然而这些方法的浸出效率较低,成本较高,而且容易造成二次污染。生物浸出技术是指通过微生物从矿石上提取有用金属的方法,是利用微生物在生命活动中自身的氧化和还原特性,使矿石资源中的有用成分氧化或还原,以水溶液中离子态或沉淀态的形式与原物质分离的方法。相对于物理方法以及化学方法,具有明显得安全性、经济性以及环境友好性,因而成为了重要的浸出重金属元素的方法之一。然而现有的生物浸出技术仅仅对几种金属元素的浸出有突破性研究,而且利用的微生物种类相对较少。近期,在利用微生物浸出锰矿中的锰离子的研究方面取得了明显的进展,然而研究的重心主要集中在用氧化亚铁硫杆菌等常用的微生物浸出贫矿中的锰以及海洋中锰结核的锰。电解锰废渣,是在电解金属锰的过程中产生含有大量金属锰的酸性渣,由于废渣中的锰含量相对较高,因而可视为贫锰矿,对于废渣中锰离子的浸出研究尚停留在化学浸出阶段,少量的研究采用化学浸出与物理浸出相结合的方式进行。尽管电解锰废渣堆积场的环境条件非常的恶劣,但是废渣中还是含有一定的微生物,而这些微生物对于锰离子肯定有一定的耐受性,基于这一理论,本研究首次从电解锰废渣中分离筛选出高耐锰的菌株,并利用分离驯化出来的菌株浸出废渣中的锰。首先,本论文首次使用从电解锰废渣中分离纯化出来的两株菌株来进行微生物浸锰研究,与传统的化学浸出以及化学浸出和物理浸出相结合的浸出方式相比具有很高的创新性,并通过微生物的生长形态观察、显微形态观察以及分子生物学的方法对两种高耐锰菌分别进行了鉴定,确定了两种浸锰微生物的名称分别为Fusarium sp.和Serratia sp.。随后,用从废渣中分离得到的两种微生物Fusarium sp.和Serratia. sp.进行电解锰废渣的生物浸出实验,考察了在浸出过程中pH值、固液比、温度、摇床转速、微生物的接种量、亚铁离子的含量、汞离子的含量等因素分别对于Fusarium sp.和Serratia. sp.两种微生物浸出废渣中锰离子浸出效率的影响,并对两种菌的浸出效率做了对比,确定了Fusarium sp.和Serratia. sp.的最佳浸出条件:Serratia. sp.的最佳浸出条件为:37℃,固液比为10%,pH值6,2 mL的接种量,150 rpm的摇床转速,加入10 g/L的亚铁离子的情况下浸出74 h,,最高的浸出效率达到76.9%;Fusarium sp.的最佳浸出条件为:28℃,固液比为10%,pH值4,2 mL的接种量,150 rpm的摇床转速,加入10 g/L的亚铁离子的情况下浸出74 h,浸出效率达到82.5%。微生物浸出的机理有两种直接作用和间接作用,本研究通过分析浸出液的成分,以及浸出液中产生的有机酸的浓度随浸出时间的变化,pH值随浸出时间的变化,浸出前后电解锰废渣的表面形态变化以及浸出前后电解锰废渣中重金属离子的形态对比分析并结合最佳条件下的浸出效率随时间的变化,分析了Fusarium sp.在基础电解锰废渣中锰离子的浸出机理,研究的结果表明:Fusarium sp.能直接作用于电解锰废渣的表面,使废渣表面由紧蹙变得疏松,Fusarium sp.在浸出过程中产生的有机酸(主要为草酸、柠檬酸、苹果酸以及琥珀酸)能与电解锰废渣发生氧化还原、螯合、络合等化学反应,从而促进了废渣中高价的锰离子转化为二价的锰离子而进入到浸出液中。在对浸出机制进行了研究了后,对生物浸出废渣中锰的实验进行了扩大研究,并从经济效益的角度以及工艺应用的角度对浸出过程中的一些因素进行了改进,如碳源的改进,曝气装置以及搅拌装置的设定等,并监控了在扩大研究过程中的pH值和溶解氧的变化,研究结果表明:葡萄糖能很好的代替蔗糖作为浸出时微生物所需的碳源,浸出过程中曝气+搅拌不仅能很好的促进微生物的生长,而且还能很好的促进微生物与废渣的充分接触,从而促进微生物与废渣的直接与间接的作用,进而提高微生物从废渣中浸出锰离子的浸出效率,随后的经济效益损益分析的结果表明,采用生物浸出的方法,1吨锰矿的浸出成本节约大约520元,表明两种微生物浸出电解锰废渣中的锰离子不仅具有经济效益,同时还具有环境效益。本研究首次采用从电解锰废渣中分离得到的微生物菌株,并反过来利用这两种微生物对废渣进行生物浸出实验,研究表明这两种菌株对于废渣中的锰离子有很强的生物浸出能力,通过各种浸出条件的改进使其具有更高的工艺应用价值。本研究为微生物浸锰研究提供了新的微生物种类,同时为电解锰废渣的资源化利用提供了新的更经济更环保的途径,为电解锰废渣的资源化利用从实验室走向工业实际应用提供了理论基础与技术支持。更多还原

【Abstract】 There are more and more manganese-electrolyzed slag discharged into the environment along with the fast growth of the manganese-electrolyzed industry. Because of the low pH value of the slag and with the rainfall leaching or its own leakage the plentiful of heavy metal ions contained in the slag will enter into the surface water and underground water. Even more the heavy metal ions which were entered into the surface water and the ground water will accumulate in the human body along with the food chain, and then threatens and influences the healthy of the human body. Meanwhile open-air piled up of those manganese-electrolyzed slag will destroy the ecotope environmental of the soil around the site, converted the structure of the soil, and there by influence the crops’growth. However there are also some worthy metal ions contained in the manganese- electrolyzed slag that can be recycled and reused by some certained methods. Those methods including chemical methods, physical methods and the combined chemical-physical methods, however those methods had a lot of weakness, for example: low leaching efficiency, high cost, could lead to secondary pollution and so on. Bioleaching technology is a method which can leach out the worthy metal elements from mineral ores by microorganisms’own oxidation and reduction during its vitalmovement, and let the worthy metal elements oxidized or reduced, then entered into the solution as ion form or precipitate form. Compared with chemical methods and physical methods, bioleaching method had some advantages, such as safety, economical efficiency and environmental friendly, and has become one of the most important leaching methods for leaching metal element from mineral ores. However the existing bioleaching methods just had breakthrough research development on several common metals, and used only some type of the microbiology.Recently there had some obvious developments on bioleaching of manganese ion from manganese minerals. But the main part was concentrated on bioleaching manganese from low grade manganese ores and manganese nodules in the oceans. Manganese-electrolyzed slag was an acidity slag which was abundance produced during the manganese-electrolyze industry. It can be treated as low grade manganese ores as it contained relatively high concentration of manganese element. The recently research of leach methods were remained on the chemical leaching, a few study used the combined chemical-physical methods. There still exist some microbe though the environment of the landfill were hostile, obviously those exist microbe had resistance on high concentration of manganese. Based on this suppose, we isolated some microbes from manganese-electrolyzed slag. Then we screened out two microbes which had high resistance on manganese from manganese-electrolyzed slag landfill, and then using those two microbes to conduct a study on bioleaching manganese from manganese- electrolyzed slag.Firstly, we firstly isolated and screened out two bacterial strains from manganese-electrolyzed slag to conduct a study on bioleaching of manganese from manganese-electrolyzed slag, and it had high innovation compared with the traditional chemical and combined chemical-physical leaching methods. Then we identified the two bacterial strains by the methods of growth morphology observing, micro morphology observing and molecular biology identification. After Phylogenetic Tree analysis we confirmed the name of those two bacterial strains were Fusarium sp. and Serratia sp. respectively.Following, we used those two strains Fusarium sp. and Serratia sp. conducted the bioleaching experiment, investigated some influence factors, such as pH value, solid-to-liquid ratio, temperature, rotation speed, inoculum concentrations, ferrous ion’s concentrations and mercury ion concentrations, on affecting the bioleaching efficiency and compared the bioleaching efficiency of those two strains. The result showed that the optimum bioleaching conditions for bioleaching of manganese from manganese-electrolyzed slag by Fusarium sp. and Serratia sp. were as follows: for Serratia sp.: the optimum condition was the bioleaching was conduct with 2 mL inoculum of strain, pH value 6, rotation speed 150 rpm, add 10 g/L ferrousion, 10% solid-to-liquid ratio at 37 oC for 74 h, the bioleaching efficiency can reach to 76.9%. for Fusarium sp.: the optimum condition was the bioleaching was conduct with 2 mL inoculum of strain, pH value 4, rotation speed 150 rpm, add 10 g/L ferrousion, 10% solid-to-liquid ratio at 28 oC for 74 h, the bioleaching efficiency can reach to 82.5%. Mercury ion had negative effects on bioleaching process.It seems there are two mechanisms for bioleaching, i.e. direct and indirect action. In this research, we also studied the bioleaching mechanism by following methods: component analysis of lixivium, the variation of concentrations of organic acids during bioleaching process, variation of pH value during bioleaching, surface morphology alteration of manganese-electrolyzed slag before and after bioleaching, and comparation of heavy metal ions’morphology before and after bioleaching. Then we discussed and analysis the mechanism of the bioleaching with Fusarium sp. by combined the results with the variation of bioleaching efficiency during the bioleaching process. The results showed that: Fusarium sp. can directly act on the surface of the slag, and it can produce some organic acids (mainly were oxalic acid, citric acid, malic acid, succinic acid) during the bioleaching process by its own metabolize, those organic acids can cause redox, chelation and complexation chemical reaction with manganese slag, which promoted the leaching out of manganese from the slag.After studied the mechanism of the bioleaching process, we expanded the experiment to Industrial applications, and improve some factors such as organic carbon source melioration, aerating device and stiring device setting and so on, during the bioleaching process we monitoring the variation of pH value. The result showed that: glucose can take the place of sucrose as the best organic carbon source; aerating and stiring can facilitate the bioleaching efficiency during the process because it can not only supply oxygen, but also can promote the contact of manganese slag and the fungi to improve the direct and indirect reaction. The economic loss-benefit analysis result showed that compared with the chemical leaching process, the bioleaching process can save about 520 RMB/t of manganese ores. This obviously showed that the bioleaching process had not only economic benefits, but also had environmental benefits.In this research, we firstly isolated and screened out two strains of microbe which had high resistance on manganese from manganese slag, then used those two strains conduct bioleaching experiment with the slag in turn. It’s the first time that using biological method to treat manganese-electrolyzed slag. The research indicates that those two strains had strong bioleaching ability on manganese leaching out from the slag. We improved the bioleaching conditions according the bioleaching mechanism to let those microbes had high industrial applying worthy. In this research, we not only provided a new microbe for bioleaching study, but also supported a more economic and more environmental protecting method for manganese-electrolyzed slag recycling. This study offers the ability to fully achieve of the application of manganese-electrolyzed slag reusing.更多还原