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纳米零价铁生物滤料耦合假单胞菌对氯代苯的降解效果及机理研究
Alternative TitleApplication and Mechanism for Degradation of Chlorobenzenes by Nanoscale zero-valent iron/Biofilter coupled with Pseudomonas
马建鹏
Subtype硕士
Thesis Advisor马安周
2019-06
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name理学硕士
Degree Discipline环境科学
Keyword氯代苯 纳米零价铁 生物滤料 假单胞菌,协同降解 Cbs, Nzvi, Biofilter, Pseudomonas Sp., Synergistic Degradation
Abstract

      氯代苯是一类有机污染物,由于其高毒性、持久性和迁移性,具有很高的环境风险。已有研究表明, 氯代苯类污染物 在土壤、水、空气和沉积物等环境中均检测到较高浓度 其中, 六氯苯和五氯苯 等污染物已被《斯德哥尔摩公约》列为优先污染物 因此减少或消除这类化合物对环境 保护 是非常重要的。近年来,纳米零价铁作为一种具有前途的环境污染修复 材料 得到了广泛的研究与应用。虽然纳米零价铁的高比表面积和高反应活性有利于污染物的降解,但其易聚集和易氧化等缺点 以及对污染物的降解 效果不稳定 ,在一定程度上阻碍了其在环境中的进一步应用。 微生物技术因其高效且低能耗的优点被认为是一项安全经济的环境污染治理技术,并且已经广泛地应用于各类有机物的降解。已有研究表明,多种好氧微生物表现出对低氯代苯良好的降解能力,仅有少数厌氧微生物能够降解高氯苯,且效率较低。 所以 ,本研究希望制备 一种 负载纳米零价铁的生物滤料并将其与好氧微生物耦合,提高 对 氯代苯类污染物的降解效率,实现 产物无害化 ,为含有氯代苯类有机污染物的复杂环境的修复提供参考。本研究的主要工作包括以下两个方面:
      (1)制备了以石料尾料为基础的生物滤料,通过液相还原法将纳米零价铁负载于生物滤料上,采用场发射扫描电镜、 比表面积及孔径分析 和 X射线粉末衍射 分析等手段对以上材料进行表征,获得了负载情况较好的纳米零价铁 /生物滤料 。 X射线粉末衍射 的 图谱 展现了 44.6 处 的 高 衍射峰 ,该峰为 单质铁的特征峰 ,说明纳米零价铁负载成功。 纳米零价铁 /生物滤料的比表面积可达 34.5 m² /g。电镜照片显示了在生物滤料表面孔隙中分散良好的纳米零价铁。 以 1,2,4-三氯苯和五氯苯为目标污染物,使用纳米零价铁 /生物滤料进行降解实验。 1,2,4-三氯苯12 h的去除率可达 五氯苯 48 h的去除率可达 反应过程 均 符合伪一级动力学模型, 伪一级反应速率常数 分别 为 0.1417 h-1和 0.0208 h-1。 通过测定反应体系中的羟基自由基,证实了纳米零价铁在降解过程中发生了芬顿反应 ,能够实现对 氯代苯类污染物 的脱氯作用 。
      (2)构建了纳米零价铁 /生物滤料耦合假单胞菌的协同降解体系,以五氯苯为污染物进行降解实验 48 h的去除率可达 80.2%,反应过程符合伪一级动力学模型, 伪一级反应速率常数 为 0.0336 h-1。 通过血球计数板法对细菌数量进行计算发现 ,在 假单胞菌 /纳米零价铁的体系中,细菌数量明显增加,说明细菌参与了污染物的降解过程,并摄取利用了降解产物 用于生长繁殖。通过场发射扫描电镜观察细菌形态,发现纳米零价铁附着在细菌表面,呈现出分散度良好的球形形态。根据实验结果推测 其降解机理为:生物滤料吸附五氯苯至表面孔隙中,纳米零价铁发生 芬顿 反应产生羟基自由 基对五氯苯进行脱氯,然后假单胞菌摄取利用反应产生的 低氯代苯 ,达到 脱氯 降解的效果。
      本研究构建了纳米零价铁/生物滤料耦合微生物的一种协同降解体系, 具有高效降解和 产物无害化 的优势, 为含有氯代苯类有机污染物的环境修复提供了新的方法和思路 。

Other Abstract

      Chlorobenzenes (CBs) are a group of organic pollutants that pose a high environmental risk due to their toxicity, persistence and possible transfer in the food chain. It has been shown that high concentrations of CBs have been detected in environmental units such as soil, water, air and sediments, and HCB and PeCB have been listed as priority pollutants by the Stockholm convention, therefore, it is very important to reduce or eliminate the pollution caused by such compounds. In recent years, nanoscale zero-valent iron (NZVI) has been widely studied and applied as a promising remediation material for environmental pollution. Although the high specific surface area and high reactivity of NZVI are beneficial to the degradation of pollutants, their disadvantages, such as easy aggregation and oxidation, as well as the unstable degradation efficiency of pollutants, hinder the further application in the environment to some extent. Microbial technology is known as a safe and economical environmental pollution control technology because of its high efficiency and low energy consumption, and has been widely used in the degradation of various organic substances. There have been some studies showing that a variety of aerobic microorganisms exhibit good degradation ability to low-chlorinated benzene, and only a few anaerobic microorganisms can degrade high-chlorine benzene of which degradation efficiency is low. Therefore, this study hopes to construct a novel synthetic system, containing NZVI, the biofilter and the aerobic microorganism, which can improve the degradation efficiency of CBs. To provide an important reference for the remediation of organic pollutants such as CBs in complex environments. The main work of this study includes the following two aspects:
      (1) A biofilter based on stone tailings was prepared and NZVI was loaded on biofilters by the liquid phase reduction method. The above materials were characterized by field emission scanning electron microscopy, specific surface area and pore size analyzer and X-ray powder diffraction analyzer, and then the NZVI/Biofilter with good loading conditions was obtained. The X-ray powder diffraction pattern showed the high diffraction peak at 44.6°°, which was the characteristic peak of the elemental iron, indicating NZVI was loaded successfully. The specific surface area of NZVI/Biofilter reached to 34.5m2/g, and the electron micrograph showed a good dispersion of NZVI in the surface pores of the biofilter. The degradation experiments of 1,2,4-TCB and PeCB by NZVI/Biofilter were carried out. The removal efficiency of 1,2,4-TCB after 12 h was up to 79%, and that of PeCB after 48 h was up to 57%. The reaction process was consistent with the pseudo-first-order kinetics model, and the pseudo-first-order rate constants were 0.1417h-1 and 0.0208h-1, respectively. By detecting hydroxyl radical in the reaction system, it was confirmed that Fenton reaction occurred in the dechlorination process of CBs.
      (2) A synergistic degradation system of pseudomonas sp. and NZVI/Biofilter was established. PeCB was used as the pollutant for degradation experiments, and the removal efficiency of NZVI/Biofilter reached 80% after 48 hours. The reaction process accorded with the pseudo-first-order kinetics model, and the rate constant was 0.0336 h-1. The number of bacteria was calculated by the blood cell counting plate method, and it was found that the number of bacteria was significantly increased in the JS100/NZVI system, indicating that the bacteria participated in the degradation process of pollutants and used the intermediate products for growth and reproduction. According to the SEM images of bacteria, it was found that the NZVI was attached to the surface of the bacteria, presenting a spherical shape with good dispersion. Combining with experimental results and existing researches, it was speculated that the degradation mechanism was as follows: the biofilter adsorbed PeCB into the surface pores, the NZVI generated hydroxyl radicals through Fenton reaction to dechlorinate PeCB, and then the Pseudomonas ingested and utilized the low-chlorobenzenes generated in the reaction, achieving the degradation of PeCB.
      To conclude, a synergistic system, JS100NZVI/Biofilter, is constructed, which has high degradation efficiency without harmful products, providing a new method for the restoration of the environment containing CBs.

Pages67
Language中文
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42264
Collection中国科学院环境生物技术重点实验室
Recommended Citation
GB/T 7714
马建鹏. 纳米零价铁生物滤料耦合假单胞菌对氯代苯的降解效果及机理研究[D]. 北京. 中国科学院生态环境研究中心,2019.
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