多氯联苯污染土壤的牡蛎壳改性材料修复研究
发布时间：2018-08-07 11:57
【摘要】：多氯联苯(Polychlorinated biphenyls,PCBs)是典型的持久性有机污染物。它具有难降解、高富集和能远距离迁移等特点。由于土壤是其最终归宿,因此进入环境中的PCBs最终将造成土壤的PCBs污染。目前,我国PCBs 土壤污染形势较为严峻,同时缺乏经济高效的PCBs土壤污染修复方法,使其成为环境安全和人体健康的潜在危害。牡蛎壳是天然的土壤改良剂,同时也是复合材料的优良载体。纳米铁由于其具有脱氯性,在含氯有机污染物污染的土壤中得到广泛应用。本课题以牡蛎壳为载体,利用纳米铁对其进行改性,制得纳米铁改性牡蛎壳材料,充分应用在PCBs的污染土壤中。纳米铁优越的化学脱氯性能,使改性材料兼具土壤改良和PCBs吸附固定及化学降解作用。从而起到物理-化学法联合修复的效果。既实现废弃牡蛎壳的资源利用化,又克服了纳米铁易团聚、易氧化等缺点。以期能高效经济的吸附、固化以及降解土壤中的PCBs提供技术支撑,扩大牡蛎壳的应用范围。课题首先通过原位还原负载法制得牡蛎壳改性材料。然后对牡蛎壳改性材料进行了表征,考察了其PCBs污染土壤的修复效果。由于土壤系统涉及固液两相,十分复杂,为了更好地分析改性材料对土壤中PCBs的固定和降解机理,课题首先考察了改性材料对水中PCBs的去除;在此基础上进一步研究了改性材料的PCBs污染土壤修复效果及影响因素;最后,通过动力学和等温吸附模型拟合实验数据,探究了改性材料对土壤中PCBs的固定降解机制。主要研究结果如下:(1)采用原位还原负载法制备的改性材料,通过微观结构表征结果表明,改性材料中的纳米铁高度分散,尺寸均匀且与牡蛎壳紧密结合;改性材料以牡蛎壳为载体提高了纳米铁的分散性和抗氧化性,改性材料中牡蛎壳的晶型与结构未受影响。(2)牡蛎壳改性材料对水中的PCBs去除实验表明,溶液初始浓度和温度对降解效率的影响比溶液pH值的影响更大;当改性材料投加量为0.03 g,溶液PCBs初始浓度、温度和pH分别为为5 mg/L、25℃和7时,PCBs去除率可达96%;与单独的纳米铁相比,改性材料的使用寿命更长。(3)牡蛎壳改性材料修复PCBs污染土壤实验表明,随着土壤有机质的增加,土壤的修复率降低;随着土壤温度和含水量增加土壤的修复率和改性材料对PCBs的吸附量均呈先增加后平稳的趋势。吸附过程符合准二级动力学模型。在等温吸附模型中,Langmuir方程能较好地描述改性材料的PCBs等温吸附行为。改性材料的PCBs污染土壤修复是物理吸附和化学脱氯的综合作用。
[Abstract]:Polychlorinated biphenyls (Polychlorinated) are typical persistent organic pollutants (pops). It has the characteristics of difficult degradation, high enrichment and long distance energy transport. As the soil is the ultimate destination, the PCBs entering the environment will eventually cause soil PCBs pollution. At present, the pollution situation of PCBs soil in China is severe, and the PCBs soil pollution remediation method is lack of economic and efficient, which makes it a potential harm to environmental safety and human health. Oyster shell is a natural soil modifier and an excellent carrier of composite materials. Due to its dechlorination, nanometer iron is widely used in soil contaminated with chlorinated organic pollutants. In this paper, the oyster shell was modified with nano-iron as the carrier, and the modified oyster shell material was prepared, which was fully used in the contaminated soil of PCBs. The excellent chemical dechlorination properties of nanometer iron make the modified materials have the functions of soil improvement, PCBs adsorption and fixation and chemical degradation. Thus, the physical-chemical method combined repair effect. It not only realizes the resource utilization of abandoned oyster shell, but also overcomes the disadvantages such as the agglomeration and oxidation of iron nanoparticles. In order to efficiently and economically adsorb, solidify and degrade PCBs in soil to provide technical support and expand the application of oyster shell. Firstly, the oyster shell modified material was prepared by in situ reduction loading method. Then the modified material of oyster shell was characterized and the remediation effect of PCBs contaminated soil was investigated. In order to better analyze the mechanism of PCBs immobilization and degradation in soil, the removal of PCBs in water by modified materials was investigated firstly because the soil system involved solid and liquid two-phase, which was very complex. On this basis, the remediation effect and influencing factors of modified PCBs contaminated soil were further studied. Finally, the fixed degradation mechanism of modified material to PCBs in soil was investigated by fitting experimental data with kinetics and isothermal adsorption model. The main results are as follows: (1) the modified materials were prepared by in-situ reduction loading method. The results of microstructure characterization showed that the nano-iron in the modified materials was highly dispersed, uniform in size and tightly bonded with oyster shell; The dispersion and oxidation resistance of iron nanoparticles were improved by using oyster shell as the carrier, and the crystal shape and structure of the modified material were not affected. (2) the PCBs removal experiment of oyster shell modified material in water was carried out. The effect of initial solution concentration and temperature on the degradation efficiency is greater than that of pH value, when the dosage of modified material is 0.03 g, the initial concentration of PCBs in solution is 0.03 g. The removal rate of PCBs at 5 mg / L ~ (25 鈩，
本文编号：2169949
[Abstract]:Polychlorinated biphenyls (Polychlorinated) are typical persistent organic pollutants (pops). It has the characteristics of difficult degradation, high enrichment and long distance energy transport. As the soil is the ultimate destination, the PCBs entering the environment will eventually cause soil PCBs pollution. At present, the pollution situation of PCBs soil in China is severe, and the PCBs soil pollution remediation method is lack of economic and efficient, which makes it a potential harm to environmental safety and human health. Oyster shell is a natural soil modifier and an excellent carrier of composite materials. Due to its dechlorination, nanometer iron is widely used in soil contaminated with chlorinated organic pollutants. In this paper, the oyster shell was modified with nano-iron as the carrier, and the modified oyster shell material was prepared, which was fully used in the contaminated soil of PCBs. The excellent chemical dechlorination properties of nanometer iron make the modified materials have the functions of soil improvement, PCBs adsorption and fixation and chemical degradation. Thus, the physical-chemical method combined repair effect. It not only realizes the resource utilization of abandoned oyster shell, but also overcomes the disadvantages such as the agglomeration and oxidation of iron nanoparticles. In order to efficiently and economically adsorb, solidify and degrade PCBs in soil to provide technical support and expand the application of oyster shell. Firstly, the oyster shell modified material was prepared by in situ reduction loading method. Then the modified material of oyster shell was characterized and the remediation effect of PCBs contaminated soil was investigated. In order to better analyze the mechanism of PCBs immobilization and degradation in soil, the removal of PCBs in water by modified materials was investigated firstly because the soil system involved solid and liquid two-phase, which was very complex. On this basis, the remediation effect and influencing factors of modified PCBs contaminated soil were further studied. Finally, the fixed degradation mechanism of modified material to PCBs in soil was investigated by fitting experimental data with kinetics and isothermal adsorption model. The main results are as follows: (1) the modified materials were prepared by in-situ reduction loading method. The results of microstructure characterization showed that the nano-iron in the modified materials was highly dispersed, uniform in size and tightly bonded with oyster shell; The dispersion and oxidation resistance of iron nanoparticles were improved by using oyster shell as the carrier, and the crystal shape and structure of the modified material were not affected. (2) the PCBs removal experiment of oyster shell modified material in water was carried out. The effect of initial solution concentration and temperature on the degradation efficiency is greater than that of pH value, when the dosage of modified material is 0.03 g, the initial concentration of PCBs in solution is 0.03 g. The removal rate of PCBs at 5 mg / L ~ (25 鈩，
本文编号：2169949
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