稳定纳米零价铁的制备与修复土壤中六价铬的研究

发布时间：2018-06-06 18:30

本文选题：纳米零价铁 + 聚乙烯吡咯烷酮(PVP)　；参考：《上海大学》2015年硕士论文

【摘要】：土壤是人类的重要资源,在人们的生产和生活中具有不可替代的作用。但是,随着工业和经济的快速发展,铬化合物被广泛应用于各种行业(如金属电镀、电子、制革、冶金和木材保护)。由于含铬废弃物的不当堆存和含铬废水的乱排放,导致大量铬尤其是Cr(VI)进入土壤中,引起严重的污染。Cr(VI)以其较大的毒害作用引发了一系列负面效应,影响了周围动物,植物以及人类的健康。因此,解决土壤中Cr(VI)的污染问题成为了环境工作者关注的焦点。近几年的研究表明,纳米级零价铁材料由于具有高的反应活性,可修复多种环境污染物等特点,成为目前环境污染修复技术中一个非常活跃的研究领域。但是在实际应用中纳米铁材料仍然存在一些问题需要解决,如纳米铁合成条件不易控制,极易团聚,空气稳定性差。这些因素都对纳米铁材料的制备和使用提出了严峻的挑战。本论文对纳米铁制备的液相还原法进行改进,制备出聚乙烯吡咯烷酮(PVP)和羧甲基纤维素(CMC)稳定的纳米铁材料并用于土壤Cr(VI)污染的修复。论文研究了稳定纳米铁的稳定性,考察了稳定纳米铁对土壤中Cr(VI)的去除能力,探讨了稳定纳米铁去除Cr(VI)的动力学和机理。通过实验,得到如下结果:1.通过优化制备条件得到PVP稳定纳米零价铁制备的最佳方法,PVP投加量为0.5 g、乙醇加入量为20 m L以及Fe SO4?7H2O和Na BH4的摩尔比为1:3时,得到高反应活性的纳米零价铁。表征分析结果显示,PVP稳定纳米零价铁粒径范围为50-100 nm,并具有一定的抗氧化性能。比表面积为53 m2/g。单因素实验结果表明,较高的PVP稳定纳米零价铁投加量(0.4 g/L),较低的土壤Cr(VI)初始含量(138.93 mg/kg),较低的p H值(3)时,土壤中Cr(VI)的去除率最高。根据单因素的实验结果进行正交试验,得到土壤Cr(VI)初始含量为138.93 mg/kg,p H=5,PVP稳定纳米零价铁投加量为0.3 g/L时为最优条件。PVP稳定纳米零价铁对六价铬的还原过程符合伪一级反应动力学,表观速率常数kobs=0.0093 min-1。研究了实际离子活度条件下基于电位-p H热力学计算图的六价铬的去除机制,在酸性条件下,Fe2+、HCr O4-及Cr3+为主要存在形态,有利于六价铬还原为三价铬,故在酸性条件下六价铬去除率高。在碱性条件下,Cr(OH)2+、Cr(OH)2+、Cr(OH)3、Cr(OH)4-及Fe(OH)3为主要存在形态,同时又有共沉淀物的产生,故在碱性条件下六价铬去除率低。2.通过优化制备条件得到CMC稳定纳米零价铁制备的最佳方法,CMC质量比为0.2%、CMC溶液加入量为20 m L以及Fe SO4?7H2O和Na BH4的摩尔比为1:3时,得到高反应活性的纳米零价铁。表征分析结果显示,CMC稳定纳米零价铁粒径范围为80-100 nm,并具有一定的抗氧化性能。比表面积为16 m2/g。单因素实验结果表明,较高的CMC稳定纳米零价铁投加量(0.6 g/L),较低的土壤Cr(VI)初始含量(138.93 mg/kg),较低的p H值(3)时,土壤中Cr(VI)的去除率最高。根据单因素的实验结果进行正交试验,得到土壤Cr(VI)初始含量为138.93 mg/kg,p H=5,CMC稳定纳米零价铁投加量为0.5 g/L时为最有条件。CMC稳定纳米零价铁对六价铬的还原过程符合伪二级反应动力学,表观速率常数kobs=0.0004min-1。研究了实际离子活度条件下基于电位-p H热力学计算图的六价铬的去除机制,在酸性条件下,Fe2+、HCr O4-及Cr3+为主要存在形态,有利于六价铬还原为三价铬,故在酸性条件下六价铬去除率高。在碱性条件下,Cr(OH)2+、Cr(OH)2+、Cr(OH)3、Cr(OH)4-及Fe(OH)3为主要存在形态,同时又有共沉淀物的产生,故在碱性条件下六价铬去除率低。
[Abstract]:Soil is an important resource of human beings and plays an irreplaceable role in the production and life of people. However, with the rapid development of industry and economy, chromium compounds are widely used in various industries (such as metal plating, electronics, leather making, metallurgy and wood protection). Due to the improper storage of chromium containing waste and the disorderly discharge of chromium containing wastewater, A large amount of chromium, especially Cr (VI), enters the soil, causing serious pollution of.Cr (VI) causing a series of negative effects, affecting the health of the surrounding animals, plants and human beings. Therefore, the problem of solving the pollution of Cr (VI) in the soil has become the focus of environmental workers. In recent years, studies have shown that the nanoscale zero price is zero. Because of its high reactive activity and the ability to repair a variety of environmental pollutants, iron material has become a very active research field in the remediation of environmental pollution. However, in practical applications, there are still some problems to be solved in the practical application. For example, the conditions of the nano iron are difficult to be controlled, easy to be reunited, and the stability of the air is poor. These factors have challenged the preparation and use of nanomaterials. In this paper, we improved the liquid phase reduction method prepared by nano iron, prepared PVP and CMC stabilized nano iron materials and used the remediation of soil Cr (VI) pollution. The stability of stable nano iron was studied in this paper. The removal ability of Cr (VI) in soil by stable nano iron was investigated and the kinetics and mechanism of stabilizing nano iron to remove Cr (VI) was discussed. The following results were obtained by experiments. 1. by optimizing preparation conditions, the best method of preparing PVP stable nano zero valent iron was obtained, PVP dosage was 0.5 g, ethanol added to 20 m L and Fe SO4? 7H2O and Fe SO4 When the mole ratio is 1:3, the highly reactive nano zero valent iron is obtained. The results of characterization analysis show that the PVP stable nano zero valent iron particle size range is 50-100 nm and has certain antioxidant properties. The results of a single factor experiment with a specific surface area of 53 m2/g. show that the higher PVP stable nano zero valent iron dosage (0.4 g/L), the lower soil Cr (VI) at the beginning of the experiment. When the initial content (138.93 mg/kg) and low P H value (3), the removal rate of Cr (VI) in the soil is the highest. According to the experimental results of single factor, the initial content of the soil Cr (VI) is 138.93 mg/kg, P H=5, and the PVP stable nano zero valent iron addition is the optimal condition for the reduction of the six valent chromium. The pseudo first order reaction kinetics, apparent rate constant kobs=0.0093 min-1., studied the removal mechanism of six valence chromium based on the thermodynamic calculation of the potential -p H under the actual ionic activity. Under the condition of acid, Fe2+, HCr O4- and Cr3+ are the main existing forms, which are favorable for the six valence chromium to be trivalent chromium, so the removal rate of six valence chromium under the acid condition. Under alkaline conditions, Cr (OH) 2+, Cr (OH) 2+, Cr (OH) 3, Cr (OH) 4- and Fe (3) are the main existing forms, and there are co precipitates at the same time. Therefore, under alkaline conditions, the removal rate of six valence chromium is low. The optimum method for preparing stable nano zero valent iron is obtained by optimizing preparation conditions. The mass ratio is 0.2%, and the amount of solution addition is 20. When the molar ratio of SO4? 7H2O and Na BH4 is 1:3, the highly reactive nano zero valent iron is obtained. The analysis results show that the CMC stable nano zero valent iron particle size range is 80-100 nm, and has certain antioxidant properties. The higher CMC stable nano zero valent iron dosage (0.6 g/L) is lower than the surface area of 16 m2/g.. When the initial content of soil Cr (VI) (138.93 mg/kg) and low P H value (3), the removal rate of Cr (VI) in the soil is the highest. According to the experimental results of single factor, the initial content of Cr (VI) is 138.93 mg/kg, P H=5, and the stability nanoscale zero valent iron is the most conditional zero valent iron to six valence chromium. The reduction process conforms to the pseudo two stage reaction kinetics. The apparent rate constant kobs=0.0004min-1. studies the removal mechanism of six valence chromium based on the thermodynamic calculation of the potential -p H under the actual ionic activity. Under the acidic condition, Fe2+, HCr O4- and Cr3+ are the main existing forms, which are favorable for the reduction of six valence chromium to trivalent chromium, so it is under acidic conditions. The removal rate of six valence chromium is high. Under alkaline conditions, Cr (OH) 2+, Cr (OH) 2+, Cr (OH) 3, Cr (OH) 4- and Fe (3) are the main forms, and also have common precipitates, so the removal rate of six valence chromium under alkaline conditions is low.
【学位授予单位】：上海大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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