【摘要】：多氯聯(lián)苯(Polychlorinated biphenyls,PCBs)是典型的持久性有機污染物。它具有難降解、高富集和能遠距離遷移等特點。由于土壤是其最終歸宿,因此進入環(huán)境中的PCBs最終將造成土壤的PCBs污染。目前,我國PCBs 土壤污染形勢較為嚴峻,同時缺乏經(jīng)濟高效的PCBs土壤污染修復方法,使其成為環(huán)境安全和人體健康的潛在危害。牡蠣殼是天然的土壤改良劑,同時也是復合材料的優(yōu)良載體。納米鐵由于其具有脫氯性,在含氯有機污染物污染的土壤中得到廣泛應用。本課題以牡蠣殼為載體,利用納米鐵對其進行改性,制得納米鐵改性牡蠣殼材料,充分應用在PCBs的污染土壤中。納米鐵優(yōu)越的化學脫氯性能,使改性材料兼具土壤改良和PCBs吸附固定及化學降解作用。從而起到物理-化學法聯(lián)合修復的效果。既實現(xiàn)廢棄牡蠣殼的資源利用化,又克服了納米鐵易團聚、易氧化等缺點。以期能高效經(jīng)濟的吸附、固化以及降解土壤中的PCBs提供技術支撐,擴大牡蠣殼的應用范圍。課題首先通過原位還原負載法制得牡蠣殼改性材料。然后對牡蠣殼改性材料進行了表征,考察了其PCBs污染土壤的修復效果。由于土壤系統(tǒng)涉及固液兩相,十分復雜,為了更好地分析改性材料對土壤中PCBs的固定和降解機理,課題首先考察了改性材料對水中PCBs的去除;在此基礎上進一步研究了改性材料的PCBs污染土壤修復效果及影響因素;最后,通過動力學和等溫吸附模型擬合實驗數(shù)據(jù),探究了改性材料對土壤中PCBs的固定降解機制。主要研究結果如下:(1)采用原位還原負載法制備的改性材料,通過微觀結構表征結果表明,改性材料中的納米鐵高度分散,尺寸均勻且與牡蠣殼緊密結合;改性材料以牡蠣殼為載體提高了納米鐵的分散性和抗氧化性,改性材料中牡蠣殼的晶型與結構未受影響。(2)牡蠣殼改性材料對水中的PCBs去除實驗表明,溶液初始濃度和溫度對降解效率的影響比溶液pH值的影響更大;當改性材料投加量為0.03 g,溶液PCBs初始濃度、溫度和pH分別為為5 mg/L、25℃和7時,PCBs去除率可達96%;與單獨的納米鐵相比,改性材料的使用壽命更長。(3)牡蠣殼改性材料修復PCBs污染土壤實驗表明,隨著土壤有機質的增加,土壤的修復率降低;隨著土壤溫度和含水量增加土壤的修復率和改性材料對PCBs的吸附量均呈先增加后平穩(wěn)的趨勢。吸附過程符合準二級動力學模型。在等溫吸附模型中,Langmuir方程能較好地描述改性材料的PCBs等溫吸附行為。改性材料的PCBs污染土壤修復是物理吸附和化學脫氯的綜合作用。
[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，

本文編號：2169949