【作者】 李晨桦；

【导师】 陈家玮；

【作者基本信息】 中国地质大学(北京) ， 地质工程， 2012， 硕士

【摘要】 地下水与人类的生存息息相关,然而随着人民生活水平提高和城市化进程加快,我国地下水污染问题日益凸现。有机污染物及重金属高强度场地污染对人民健康、生态环境及社会安全构成了严重威胁。地下水中的重金属Cr(Ⅵ)污染逐渐受到重视,纳米零价铁可以有效地将六价铬还原成三价铬,使其沉淀固定下来。从而将污染源区的污染物消减固定,防止其向周围扩散。然而由于纳米铁颗粒微小,易被氧化,极易团聚,自身活性受到限制,因此,纳米铁的分散性、稳定性、良好活性研究至关重要。本文采用低成本环境友好型粘土矿物膨润土作为负载材料制备膨润土负载纳米铁(B-NZVI),同时进行样品表征,并通过B-NZVI与模拟地下水含Cr(Ⅵ)溶液反应的批实验,研究其活性；通过柱实验考察膨润土负载纳米铁的迁移性及Cr(Ⅵ)在含膨润土负载纳米铁石英砂柱中的穿透曲线,这为膨润土负载纳米铁去除Cr(Ⅵ)的实际场地应用设计提供了理论实验基础。获得的主要成果如下：(1)自制的膨润土负载纳米铁个体呈球形,呈分散状负载在膨润土上。比较钠基和钙基膨润土负载纳米铁、不同膨润土含量的B-NZVI及老化五天后的除铬活性研究得出：50%钠基B-NZVI的分散性和稳定性最佳。之后实验均采用50%钠基B-NZVI进行。(2)在相同的实验条件下,含铁量相同(1g/L)的B-NZVI、NZVI和1g/L膨润土去除20mg/LCr(VI)比较得出,相同铁含量的膨润土负载纳米铁处理Cr(Ⅵ)的效率远大于纳米铁。这是因为采用膨润土作为负载材料增加纳米铁与Cr(Ⅵ)之问的电子转移,从而明显提高了铁还原Cr(Ⅵ)的能力。(3)B-NZVI对Cr(Ⅵ)的还原去除基本符合伪一级反应动力学模型。通过比较不同初始浓度B-NZVI对Cr(Ⅵ)的还原反应动力学ln(C/C0)—t直线的斜率K可知,反应的表观速率常数K随着B-NZVI初始浓度的减小而减小。(4)膨润上负载纳米铁在石英砂柱中基本无迁移,说明B-NZVI适用于点源污染。Cr(Ⅵ)在含B-NZVI石英砂柱中的穿透曲线为膨润土负载纳米铁去除Cr(VI)的实际场地应用设计提供了理论基础。更多还原

【Abstract】 Ground water is the most important water source for human’s production and life. However, with the development of living standard and urbanization, ground water pollution is becoming serious. It is hazardous to human health, ecotope and social security with the heavy metal and organic field pollutants. The issues of Cr(Ⅵ) contaminated groundwater are paid more attention recently. As Cr(Ⅵ) has high toxicity and mobility in water compared to Cr(Ⅲ), it is very important to deposit chromium by reduction of Cr(Ⅵ) into Cr(Ⅲ) using nano iron. So the contaminants in source region are stabilized and induffused from all around. While the agglomeration and oxidation of nano iron is often unavoidable due to the very small particles, it is essential to study the disperse and stability of nano iron. In this paper, bentonite was used as a porous-based support material for synthesized nano iron and the produced materials was characted with transmission electron microscope. The reactivity of bentonite-supported nano iron(B-NZVI) was evaluated by the batch tests for Cr(Ⅵ) removal in water. Colume experiments for Cr(Ⅵ) removal in porous media by B-NZVI are conducted in this study. The mobility of B-NZVI and break through curve was observed. This study provided the base of theory and experiment to the application of bentonite-supported nano iron for Cr(Ⅵ) contaminated groundwater remediation. The results are as follows.(1)Bentonite-supported nano iron was synthesized using liquidphase reduction. The particles are well sphere scattering on the bentonite. Batch tests for Cr(Ⅵ) removal by different type, content and aging bentonite-supported nano iron conducted. The fifty percent iron concentration of Na B-NZVI is better than Ca B-NZVI.(2) The removal efficiency of B-NZVI is better than NZVI comparing the same iron content (1g/L) B-NZVI, NZVI and1g/L bentonite. The bentonite enhanced the electron transfer between iron and Cr(VI)。 (3)Reduction kinetics of Cr(Ⅵ) by B-NZVI were described by a pseudo first-order reaction. Kinetics studies of Cr(Ⅵ) reduction using B-NZVI suggested that the reactivity of NZVI particles supported on bentonite were decreased significantly with the decrease of intial iron content.(4) Colume experiments showed that the B-NZVI was no migratory in the colume packed silicon dioxide. It is obtained that the breakthough curve of Cr(Ⅵ) in the colume.更多还原