改性沸石負(fù)載零價(jià)鐵處理水中六價(jià)鉻的研究
發(fā)布時(shí)間：2018-12-21 17:56
【摘要】：改性沸石和零價(jià)鐵粉已用做PRB的填料,用于六價(jià)鉻污染的地下水的修復(fù)。將改性沸石和零價(jià)鐵聯(lián)合使用,利用改性沸石的吸附能力和零價(jià)鐵的還原能力,能獲得增強(qiáng)型的處理六價(jià)鉻的復(fù)合填料。制備上述復(fù)合填料的關(guān)鍵如下:1)解決零價(jià)鐵的流失問題。零價(jià)鐵粒徑越小反應(yīng)活性越好,但當(dāng)其粒徑過小會穿過PRB填充材料空隙隨水流失。2)保證改性沸石的吸附能力不會失去。在制備填料過程中難免會引入其他物質(zhì)可能會和改性劑反應(yīng),從而使其失去吸附能力。針對上述問題,本文利用海藻酸鹽與CaCl2的轉(zhuǎn)凝膠反應(yīng)固定微米級零價(jià)鐵;用十六烷基三甲基溴化銨(HDTMA-Br)對天然沸石進(jìn)行改性。從而制得增強(qiáng)型的改性沸石載鐵的復(fù)合填料。制備復(fù)合填料,考察其是否解決上述問題。對制備的填料進(jìn)行掃描電鏡分析發(fā)現(xiàn)零價(jià)鐵能分散的固定在改性沸石表面。同時(shí)對與六價(jià)鉻反應(yīng)后的填料的表面用X射線光電子能譜儀(XPS)進(jìn)行分析,發(fā)現(xiàn)填料表面既有三價(jià)鉻也有六價(jià)鉻,證明了填料既具有還原性也具有吸附性。用小試考察復(fù)合填料去除Cr(VI)的過程的性能。實(shí)驗(yàn)表明Cr(VI)去除的現(xiàn)象能用偽二級吸附動力學(xué)方程描述,平衡吸附量qe和反應(yīng)速率常數(shù)k呈相反的變化趨勢。鐵粉含量為5.4%的材料性能較好:qe為0.96mg/g,k為0.011g/(mg·h);在Cr(VI)濃度為70mg/L時(shí),上述鐵含量的復(fù)合材料仍具有較高的處理性能,其qe和k分別為1.29 mg/g,0.0094 g/(mg·h)。用Langmuir吸附等溫?cái)M合填料對Cr(VI)的吸附數(shù)據(jù)所得最大吸附量為2.49mg/L。當(dāng)pH7時(shí),填料對六價(jià)鉻具有較高的去除效率。用柱實(shí)驗(yàn)?zāi)M復(fù)合填料在多離子共存的條件下對六價(jià)鉻的去除效果。通過實(shí)驗(yàn)柱和其他柱子的對比證明在固定鐵粉時(shí)選擇CaCl2使海藻酸鹽轉(zhuǎn)凝膠,引入的氯離子與改性劑HDTMA-Br反應(yīng)所形成的HDTMA-Cl仍能和六價(jià)鉻發(fā)生離子交換進(jìn)而去除六價(jià)鉻,不會影響去除效果�；诤Ｔ逅猁}和CaCl2的轉(zhuǎn)凝膠反應(yīng),制得了增強(qiáng)型的去除六價(jià)鉻的填料。制備的填料固定住了零價(jià)鐵粉,解決了鐵粉流失的問題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.
【學(xué)位授予單位】：北京工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：X523
本文編號：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.
【學(xué)位授予單位】：北京工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：X523
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 任剛;崔福義;;改性天然沸石去除水中氨氮的研究[J];環(huán)境污染治理技術(shù)與設(shè)備;2006年03期
，本文編號：2389258
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