铅锌矿区先锋植物根际土壤耐性微生物的筛选及其吸附机理研究

发布时间：2018-07-13 11:27

【摘要】：随着采矿、冶炼、电镀、电子及燃料生产等行业的快速发展,越来越多的铅锌等重金属通过多种途径进入土壤或水体环境中,对生态环境和人类健康造成了严重威胁。近年来,利用耐性微生物治理重金属污染已成为一个新型的研究领域。本研究通过从湖南某铅锌矿区的先锋植物根际土壤中,分离、筛选出一株对铅锌耐性较强的菌株,考察了其对铅、锌去除能力的主要影响因素,并对其吸附机理进行初步探讨,以期为今后重金属污染微生物修复的工业化应用提供参考。本论文研究的主要内容和结论如下：(1)从铅锌矿区纯化分离出11株菌株,初步筛选得到3株耐性菌,选定其中耐性最高的菌株HA作为本研究的实验菌株,菌株HA对铅、锌离子都有较高耐性的,且其对铅离子的去除效率高于锌离子。通过对菌株HA的形态及DNA测序分析,最终鉴定HA为米曲霉(Aspergillus oryzae)。(2)通过单因素实验及正交实验对耐性菌HA吸附铅锌离子的环境条件进行了优化,得到如下结论：①在初始铅、锌浓度的实验范围内(100-800 mg/L),HA对铅、锌离子的去除率随着其初始浓度增加而减小,当铅、锌初始浓度为100 mg/L、pH为5.0时,HA对铅、锌离子的去除率均达到最高,分别为97.8%、54.1%；生长曲线分析表明,25 h后HA的生长进入平稳期,且对铅、锌离子的去除率趋于稳定。当HA接种量为1 mL时,其对铅、锌去除率的增长率达到最大。②在单因素实验结果的基础上,选择重金属离子的初始浓度、pH、接种量、吸附时间四因素中,较显著的3个水平,进行正交实验,最终确定HA吸附铅、锌离子的最优方案都为：初始浓度为100mg/L时,培养基pH为5.5,接种量为菌浓度为0.01 g/mL的菌液1.5 mL,吸附时间为3 d。(3)通过等温吸附模型、动力学分析、扫描电镜、能谱分析、红外光谱等手段对耐性菌HA吸附铅和锌离子的机理进行初步探讨,并对HA细胞吸附铅、锌的吸附部位进行了初步研究,得到如下结论：①对菌株HA吸附铅、锌离子的吸附等温模式和吸附动力学进行分析,发现HA对铅、锌的吸附过程满足Langmuir吸附模型,其吸附以单层吸附为主。在动态吸附过程中,HA对Pb2+、Zn2+离子吸附性能与准二级动力学吸附方程的拟合程度更高,且对Pb2+的吸附效果明显高于Zn2+。②对HA细胞吸附铅、锌离子的吸附部位进行研究,结果表明耐性菌株HA对Pb2+、Zn2+的生物吸附和累积主要以细胞壁吸附和细胞内累积为主,其中胞壁吸附量高于胞内累积量,说明菌株HA细胞壁上的某些成分及活性基团对Pb2+、Zn2+的结合能力较强。③扫描电镜和能谱分析结果表明在吸附Pb2+、Zn2+后菌株表面有较多含铅、锌的沉淀物。IR分析表明：HA细胞中羟基、烷基、酰胺基、羰基、磷酸基等参与了Pb2+、Zn2+的吸附,使特征峰吸收强度和位置都出现不同程度的变化。
[Abstract]:With the rapid development of mining, smelting, electroplating, electronics and fuel production, more and more heavy metals, such as lead and zinc, enter the soil or water environment through many ways, which pose a serious threat to the ecological environment and human health. In recent years, the treatment of heavy metal pollution by tolerant microorganisms has become a new research field. In this study, a strain with strong tolerance to lead and zinc was isolated from the rhizosphere soil of a pioneer plant in a lead-zinc mining area in Hunan Province. The main factors affecting the removal capacity of lead and zinc were investigated, and the adsorption mechanism was preliminarily discussed. In order to provide reference for the industrial application of heavy metal contaminated microorganism remediation in the future. The main contents and conclusions of this paper are as follows: (1) 11 strains were isolated from lead-zinc mining area, and 3 resistant strains were screened. The most resistant strain HA was selected as the experimental strain in this study. Zinc ion has higher tolerance, and its removal efficiency of lead ion is higher than that of zinc ion. By analyzing the morphology and DNA sequencing of the strain HA, the HA was identified as (Aspergillus oryzae). (2. The environmental conditions for the adsorption of lead and zinc ions by the resistant strain HA were optimized by single factor experiment and orthogonal experiment. In the experimental range of zinc concentration (100-800 mg / L), the removal rate of zinc ion decreased with the increase of the initial concentration of lead and zinc. When the initial concentration of lead and zinc was 100 mg / L ~ (-1) pH 5.0, the removal rate of lead and zinc ions reached the highest, which were 97.8mg / L ~ 54.1, respectively. Growth curve analysis showed that the growth of HA reached a stable stage after 25 h, and the removal rate of lead and zinc ions tended to be stable. When the inoculation amount of HA was 1 mL, the removal rate of lead and zinc reached the maximum of .2. On the basis of the results of single factor experiments, three levels of heavy metal ions were selected as follows: pH value, inoculation amount and adsorption time. The results of orthogonal experiment showed that the best schemes for adsorption of lead and zinc ions by HA were as follows: when the initial concentration was 100 mg / L, the medium pH was 5.5, the inoculation amount was 1.5 mL of bacteria concentration 0.01 g / mL, and the adsorption time was 3 days. (3) the isothermal adsorption model was used. Kinetic analysis, scanning electron microscopy, energy dispersive analysis and infrared spectroscopy were used to study the mechanism of adsorption of lead and zinc ions by HA, and the adsorption sites of lead and zinc on HA cells were also studied. The results showed that the adsorption isotherm and kinetics of lead and zinc ions were analyzed. It was found that the adsorption process of HA for lead and zinc was consistent with Langmuir adsorption model, and monolayer adsorption was the main adsorption process. The adsorption of Pb ~ (2 +) ~ (2 +) and Zn ~ (2 +) on HA was better than that of Zn _ (2) 2 on HA, and the adsorption sites of Pb ~ (2 +) and Zn ~ (2 +) were higher than that of Zn _ (2) 2. The results showed that the biosorption and accumulation of Pb _ 2 ~ (2 +) Zn _ (2) by the tolerant strain HA were mainly cell wall adsorption and intracellular accumulation, in which the cell wall adsorption was higher than the intracellular accumulation. The results showed that the binding ability of some components and active groups on HA cell wall to Pb 2 + Zn 2 was stronger. 3. The results of SEM and EDS showed that there was more lead on the surface of the strain after adsorption of Pb 2 + Zn 2. Ir analysis of zinc precipitates showed that hydroxyl, alkyl, amide, carbonyl and phosphate groups were involved in the adsorption of Pb ~ (2 +) ~ (2 +) Zn _ (2), and the absorption intensity and position of the characteristic peaks were changed in different degrees.
【学位授予单位】：中南林业科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X172

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