粘土矿物强化零价铁去除废水中重金属污染物的作用研究
发布时间：2018-10-23 12:41
【摘要】：零价铁作为活性介质的可渗透反应墙(Fe0-PRB),被认为是一种能替代传统抽取处理、最具发展潜力的原位修复地下水技术,但在修复过程中零价铁反应活性的降低和渗透能力的减弱,是影响Fe0-PRB使用寿命、制约其实际应用的最重要因素。本文选择两种重金属离子(阴离子Se O42-(Se(VI)和阳离子Pb2+)作目标污染物,用连续柱试验方法模拟Fe0-PRB技术,将对其具有较强吸附作用的荷正电性的改性膨润土—羟基铝柱撑膨润土(Al-bent)和三种荷负电性的天然粘土矿物(海泡石:Sepiolite,钙基膨润土:Ca-bent,高岭土:Kaoline)分别与铁粉、砂均匀混合,用作PRB中的混合活性材料,比较研究了各种粘土对Fe0-PRB去除重金属污染物的强化作用和地下水中常见共存组分(腐殖酸(HA)和四种阴离子(Cl-、NO3-、HCO3-和SO42-))对Se O42-去除作用的影响;结合同步辐射X-射线吸收精细结构X-ray Absorption Fine Stucture,XAFS)光谱技术和X-射线衍射仪(Xray diffraction,XRD)等现代分析方法考察粘土在Fe0-PRB去除重金属污染物的协同作用机制。主要结果如下:1.对Se O42-具有良好吸附作用的Al-bent与Fe0、砂混合得到的Fe0/Al-bent/砂反应体系对Se O42-的还原去除能力明显高于Fe0/砂,也远高于Fe0/砂与Al-bent/砂体系对Se O42-去除率的加和,显示Al-bent和Fe0之间存在明显的协同效应。其协同作用主要源于:Al-bent加入使Se O42-在Fe0表面得到富集,促进了两者之间的电子转移,从而增强了Fe0的还原能力;表面富含的Si-OH,Al-OH的Al-bent能够缓冲反应介质的p H,从而可减少铁表面的腐蚀产物;铁表面的腐蚀产物还能转移到Al-bent,从而延长铁的反应寿命。此外,XAFS测定结果表明Al-bent的加入能有效促进Fe0将Se(VI)还原成溶解性更低,毒性更小的Se(-II)或Se(0)。2.腐殖酸(HA)和常见的共存阴离子(Cl-、NO3-、HCO3-和SO42-)均能降低Fe0/Al-bent/砂和Fe0/砂对Se(VI)的去除率,但由于Al-bent对这些共存物质较强的吸附作用,因而可明显弱化这种抑制效应。3.将三种天然粘土矿物分别与Fe0、砂均匀混合,均能显著提高对合成废水中Pb2+的去除能力,去除率与相应粘土吸附Pb2+的能力成正相关,即:Sepiolite/Fe0/砂Ca-bent/Fe0/砂Kaoline/Fe0/砂Fe0/砂。
[Abstract]:The permeable reactive wall (Fe0-PRB) of zero-valent iron as an active medium is considered as an in situ remediation technology which can replace the traditional extraction treatment and has the most potential development. However, in the process of remediation, the activity of zero-valent iron reaction decreases and the permeability decreases. It is the most important factor that affects the service life of Fe0-PRB and restricts its practical application. In this paper, two kinds of heavy metal ions (anionic Se O42-( Se (VI) and cationic Pb2) were selected as target pollutants, and Fe0-PRB technique was simulated by continuous column test. The positively charged modified bentonite (Al-bent) and three kinds of natural clay minerals (sepiolite: Sepiolite, calcium-based bentonite: Ca-bent, kaolin), which have strong adsorption effect, were mixed with iron powder and sand, respectively, and three kinds of natural clay minerals (sepiolite: Sepiolite, calcium bentonite: Ca-bent, kaolin) were mixed with iron powder and sand. As a mixed active material in PRB, the enhancement effect of various clay on the removal of heavy metal pollutants by Fe0-PRB and the effects of common coexisting components (HA) humic acid and four anions (Cl-,NO3-,HCO3- and SO42-) on Se O 42-removal in groundwater were compared. Combined with synchrotron radiation X-ray absorption fine structure (X-ray Absorption Fine Stucture,XAFS) spectroscopy and X-ray diffractometer (Xray diffraction,XRD), the synergistic mechanism of removing heavy metal pollutants from clay in Fe0-PRB was investigated. The main results are as follows: 1. The reduction ability of Se O 42- by Fe0/Al-bent/ sand reaction system with good adsorption of Se O 42- and Fe0, sand was significantly higher than that of Fe0/ sand, and the addition of Fe0/ sand and Al-bent/ sand system to Se O 42-removal rate was much higher than that of Fe0/ sand and Al-bent/ sand system, and the removal rate of Se O 42- was much higher than that of Fe0/ sand and Al-bent/ sand system. There is obvious synergistic effect between Al-bent and Fe0. The synergistic effect is mainly due to the fact that the addition of Al-bent enriches Se O42- on the surface of Fe0 and promotes the electron transfer between them, thus enhancing the reduction ability of Fe0. The Al-bent rich in Si-OH,Al-OH on the surface can buffer the pH of the reaction medium, thus reducing the corrosion products on the surface of iron, and the corrosion products on the surface of iron can also be transferred to Al-bent, thus prolonging the reaction life of iron. In addition, XAFS results showed that the addition of Al-bent could effectively promote the reduction of Se (VI) by Fe0 to Se (- II) or Se (0). 2 with lower solubility and less toxicity. Both humic acid (HA) and common coexisting anions (Cl-,NO3-,HCO3- and SO42-) can reduce the removal rate of Se (VI) from Fe0/Al-bent/ sand and Fe0/ sand, but the inhibition effect can be weakened obviously because of the strong adsorption effect of Al-bent on these coexisting compounds. When three kinds of natural clay minerals were mixed with Fe0, sand uniformly, the removal rate of Pb2 in synthetic wastewater was significantly improved, and the removal rate was positively correlated with the ability of corresponding clay to adsorb Pb2, that is, Sepiolite/Fe0/ sand, Ca-bent/Fe0/ sand, Kaoline/Fe0/ sand, Fe0/ sand.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O647.3;X703
本文编号：2289271
[Abstract]:The permeable reactive wall (Fe0-PRB) of zero-valent iron as an active medium is considered as an in situ remediation technology which can replace the traditional extraction treatment and has the most potential development. However, in the process of remediation, the activity of zero-valent iron reaction decreases and the permeability decreases. It is the most important factor that affects the service life of Fe0-PRB and restricts its practical application. In this paper, two kinds of heavy metal ions (anionic Se O42-( Se (VI) and cationic Pb2) were selected as target pollutants, and Fe0-PRB technique was simulated by continuous column test. The positively charged modified bentonite (Al-bent) and three kinds of natural clay minerals (sepiolite: Sepiolite, calcium-based bentonite: Ca-bent, kaolin), which have strong adsorption effect, were mixed with iron powder and sand, respectively, and three kinds of natural clay minerals (sepiolite: Sepiolite, calcium bentonite: Ca-bent, kaolin) were mixed with iron powder and sand. As a mixed active material in PRB, the enhancement effect of various clay on the removal of heavy metal pollutants by Fe0-PRB and the effects of common coexisting components (HA) humic acid and four anions (Cl-,NO3-,HCO3- and SO42-) on Se O 42-removal in groundwater were compared. Combined with synchrotron radiation X-ray absorption fine structure (X-ray Absorption Fine Stucture,XAFS) spectroscopy and X-ray diffractometer (Xray diffraction,XRD), the synergistic mechanism of removing heavy metal pollutants from clay in Fe0-PRB was investigated. The main results are as follows: 1. The reduction ability of Se O 42- by Fe0/Al-bent/ sand reaction system with good adsorption of Se O 42- and Fe0, sand was significantly higher than that of Fe0/ sand, and the addition of Fe0/ sand and Al-bent/ sand system to Se O 42-removal rate was much higher than that of Fe0/ sand and Al-bent/ sand system, and the removal rate of Se O 42- was much higher than that of Fe0/ sand and Al-bent/ sand system. There is obvious synergistic effect between Al-bent and Fe0. The synergistic effect is mainly due to the fact that the addition of Al-bent enriches Se O42- on the surface of Fe0 and promotes the electron transfer between them, thus enhancing the reduction ability of Fe0. The Al-bent rich in Si-OH,Al-OH on the surface can buffer the pH of the reaction medium, thus reducing the corrosion products on the surface of iron, and the corrosion products on the surface of iron can also be transferred to Al-bent, thus prolonging the reaction life of iron. In addition, XAFS results showed that the addition of Al-bent could effectively promote the reduction of Se (VI) by Fe0 to Se (- II) or Se (0). 2 with lower solubility and less toxicity. Both humic acid (HA) and common coexisting anions (Cl-,NO3-,HCO3- and SO42-) can reduce the removal rate of Se (VI) from Fe0/Al-bent/ sand and Fe0/ sand, but the inhibition effect can be weakened obviously because of the strong adsorption effect of Al-bent on these coexisting compounds. When three kinds of natural clay minerals were mixed with Fe0, sand uniformly, the removal rate of Pb2 in synthetic wastewater was significantly improved, and the removal rate was positively correlated with the ability of corresponding clay to adsorb Pb2, that is, Sepiolite/Fe0/ sand, Ca-bent/Fe0/ sand, Kaoline/Fe0/ sand, Fe0/ sand.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O647.3;X703
【参考文献】
相关期刊论文 前1条
1 贾广宁;重金属污染的危害与防治[J];有色矿冶;2004年01期
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