改性沸石负载零价铁处理水中六价铬的研究
发布时间：2018-12-21 17:56
【摘要】：改性沸石和零价铁粉已用做PRB的填料,用于六价铬污染的地下水的修复。将改性沸石和零价铁联合使用,利用改性沸石的吸附能力和零价铁的还原能力,能获得增强型的处理六价铬的复合填料。制备上述复合填料的关键如下:1)解决零价铁的流失问题。零价铁粒径越小反应活性越好,但当其粒径过小会穿过PRB填充材料空隙随水流失。2)保证改性沸石的吸附能力不会失去。在制备填料过程中难免会引入其他物质可能会和改性剂反应,从而使其失去吸附能力。针对上述问题,本文利用海藻酸盐与CaCl2的转凝胶反应固定微米级零价铁;用十六烷基三甲基溴化铵(HDTMA-Br)对天然沸石进行改性。从而制得增强型的改性沸石载铁的复合填料。制备复合填料,考察其是否解决上述问题。对制备的填料进行扫描电镜分析发现零价铁能分散的固定在改性沸石表面。同时对与六价铬反应后的填料的表面用X射线光电子能谱仪(XPS)进行分析,发现填料表面既有三价铬也有六价铬,证明了填料既具有还原性也具有吸附性。用小试考察复合填料去除Cr(VI)的过程的性能。实验表明Cr(VI)去除的现象能用伪二级吸附动力学方程描述,平衡吸附量qe和反应速率常数k呈相反的变化趋势。铁粉含量为5.4%的材料性能较好:qe为0.96mg/g,k为0.011g/(mg·h);在Cr(VI)浓度为70mg/L时,上述铁含量的复合材料仍具有较高的处理性能,其qe和k分别为1.29 mg/g,0.0094 g/(mg·h)。用Langmuir吸附等温拟合填料对Cr(VI)的吸附数据所得最大吸附量为2.49mg/L。当pH7时,填料对六价铬具有较高的去除效率。用柱实验模拟复合填料在多离子共存的条件下对六价铬的去除效果。通过实验柱和其他柱子的对比证明在固定铁粉时选择CaCl2使海藻酸盐转凝胶,引入的氯离子与改性剂HDTMA-Br反应所形成的HDTMA-Cl仍能和六价铬发生离子交换进而去除六价铬,不会影响去除效果。基于海藻酸盐和CaCl2的转凝胶反应,制得了增强型的去除六价铬的填料。制备的填料固定住了零价铁粉,解决了铁粉流失的问题并且保留了改性沸石的吸附性。
[Abstract]:Modified zeolite and zero valent iron powder have been used as fillers of PRB for remediation of hexavalent chromium contaminated groundwater. By using the modified zeolite and zero-valent iron in combination with the adsorption capacity of the modified zeolite and the reduction ability of the zero-valent iron, an enhanced composite filler for the treatment of hexavalent chromium can be obtained. The key points of preparing the composite fillers are as follows: 1) to solve the loss of zero valent iron. The smaller the particle size of zero-valent iron, the better the reaction activity, but when the particle size is too small, it will pass through the pore space of PRB filled material with water loss. 2) the adsorption ability of modified zeolite will not be lost. It is inevitable that other substances may react with modifiers during the preparation of fillers, which makes them lose their adsorption capacity. In order to solve the above problems, the zero-valent iron of micron order was fixed by the reaction of alginate with CaCl2, and the natural zeolite was modified by cetyltrimethylammonium bromide (HDTMA-Br). Thus, the composite filler of the enhanced zeolite loaded with iron was prepared. The composite fillers were prepared to investigate whether they could solve the above problems. Scanning electron microscopy (SEM) analysis of the prepared fillers showed that zero valent iron could be dispersed on the surface of modified zeolite. At the same time, the surface of the filler after reaction with hexavalent chromium was analyzed by X-ray photoelectron spectroscopy (XPS). It was found that there were both trivalent chromium and hexavalent chromium on the surface of the filler, which proved that the filler had both reductive and adsorptive properties. The performance of Cr (VI) removal with composite fillers was investigated in a small scale. The experimental results show that the phenomenon of Cr (VI) removal can be described by pseudo-second-order adsorption kinetic equation. The equilibrium adsorption amount qe and the reaction rate constant k show a reverse trend. The material with 5.4% iron powder has better properties: qe is 0.96 mg / g / g = 0.011g/ (mg h);. When the concentration of Cr (VI) was 70mg/L, the composites with iron content still had higher treatment properties, their qe and k were 1.29 mg/g,0.0094 g / (mg h)., respectively. The maximum adsorption capacity of Cr (VI) was 2.49 mg / L by Langmuir adsorption isotherm fitting. When pH7, the filler has a higher removal efficiency of hexavalent chromium. The column experiment was used to simulate the removal effect of hexavalent chromium by the composite filler under the condition of multi-ion coexistence. The comparison between the experimental column and other columns shows that CaCl2 is selected to transfer alginate into gel when fixing iron powder, and the HDTMA-Cl formed by the reaction of chloride ion with modifier HDTMA-Br can still exchange with hexavalent chromium and remove hexavalent chromium. Will not affect the removal effect. Based on the transgel reaction of alginate and CaCl2, an enhanced packing for removal of hexavalent chromium was prepared. The prepared filler fixed zero valent iron powder, solved the problem of iron powder loss and retained the adsorbability of modified zeolite.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X523
本文编号：2389258
[Abstract]:Modified zeolite and zero valent iron powder have been used as fillers of PRB for remediation of hexavalent chromium contaminated groundwater. By using the modified zeolite and zero-valent iron in combination with the adsorption capacity of the modified zeolite and the reduction ability of the zero-valent iron, an enhanced composite filler for the treatment of hexavalent chromium can be obtained. The key points of preparing the composite fillers are as follows: 1) to solve the loss of zero valent iron. The smaller the particle size of zero-valent iron, the better the reaction activity, but when the particle size is too small, it will pass through the pore space of PRB filled material with water loss. 2) the adsorption ability of modified zeolite will not be lost. It is inevitable that other substances may react with modifiers during the preparation of fillers, which makes them lose their adsorption capacity. In order to solve the above problems, the zero-valent iron of micron order was fixed by the reaction of alginate with CaCl2, and the natural zeolite was modified by cetyltrimethylammonium bromide (HDTMA-Br). Thus, the composite filler of the enhanced zeolite loaded with iron was prepared. The composite fillers were prepared to investigate whether they could solve the above problems. Scanning electron microscopy (SEM) analysis of the prepared fillers showed that zero valent iron could be dispersed on the surface of modified zeolite. At the same time, the surface of the filler after reaction with hexavalent chromium was analyzed by X-ray photoelectron spectroscopy (XPS). It was found that there were both trivalent chromium and hexavalent chromium on the surface of the filler, which proved that the filler had both reductive and adsorptive properties. The performance of Cr (VI) removal with composite fillers was investigated in a small scale. The experimental results show that the phenomenon of Cr (VI) removal can be described by pseudo-second-order adsorption kinetic equation. The equilibrium adsorption amount qe and the reaction rate constant k show a reverse trend. The material with 5.4% iron powder has better properties: qe is 0.96 mg / g / g = 0.011g/ (mg h);. When the concentration of Cr (VI) was 70mg/L, the composites with iron content still had higher treatment properties, their qe and k were 1.29 mg/g,0.0094 g / (mg h)., respectively. The maximum adsorption capacity of Cr (VI) was 2.49 mg / L by Langmuir adsorption isotherm fitting. When pH7, the filler has a higher removal efficiency of hexavalent chromium. The column experiment was used to simulate the removal effect of hexavalent chromium by the composite filler under the condition of multi-ion coexistence. The comparison between the experimental column and other columns shows that CaCl2 is selected to transfer alginate into gel when fixing iron powder, and the HDTMA-Cl formed by the reaction of chloride ion with modifier HDTMA-Br can still exchange with hexavalent chromium and remove hexavalent chromium. Will not affect the removal effect. Based on the transgel reaction of alginate and CaCl2, an enhanced packing for removal of hexavalent chromium was prepared. The prepared filler fixed zero valent iron powder, solved the problem of iron powder loss and retained the adsorbability of modified zeolite.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X523
【参考文献】
相关期刊论文 前1条
1 任刚;崔福义;;改性天然沸石去除水中氨氮的研究[J];环境污染治理技术与设备;2006年03期
，本文编号：2389258
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