表面改質奈米零價鐵對地下水DNAPL污染物現址整治之研究

In-Situ Decontamination of DNAPLs in Groundwater by Surface-modified Zero-valent Iron Nanoparticles

陳重諭(Chung-Yu Chen)

指導教授 ： 林錕松

元智大學/工程學院/化學工程與材料科學學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00018

摘要

隨著台灣科技工業的發展，在眾多工業製程中，含氯有機化合物因具有特殊物化特性，因此被廣泛使用。而近年來意外排放和使用過程中不當處置，造成含氯有機化合物大量進入土壤和地下水層中，因此對環境的衝擊格外受到重視。本研究之主要目的是探討利用化學還原法製備奈米零價鐵微粒(ZVIN)，經由表面包覆高分子有機物使ZVIN懸浮於水相中，將其應用於受DNAPLs污染物污染之現地場址整治，其結果藉由場發掃描式電子顯微鏡(FE-SEM)、X光粉末繞射儀(XRD)、化學分析電子光譜儀(ESCA)、透式電子顯微鏡(TEM)及地電阻顯影儀(RPI)，測量懸浮ZVIN溶液與DNAPLs污染地下水體反應後之變化、結構分析及DNAPLs污染物之遷移情形，以期望進一步了解利用懸浮ZVIN溶液，以直接注入法處理現地場址污染地下水體之效能及可行性。
實驗室合成之ZVIN於氬氣下經燈照法烘乾並惰化後XRD圖譜與資料庫標準品相符，且自行合成之奈米ZVIN在FE-SEM分析中，粒徑為20~120 nm之球形顆粒；由XRD分析結果顯示，在2θ = 44.59出現一主要零價鐵訊號，經BET測量其比表面積為34.7 m2/g；亦利用ESCA分析ZVIN表面成份，結果表示Fe/O比例為1.33，並含有FeO、Fe3O4和FeSO4等組成在合成之ZVIN上；而經聚乙基亞胺(PEI)改質後之ZVIN，由FE-SEM及TEM分析可知，PEI/ZVIN粒徑在20~80 nm間，其XRD分析在2θ = 44.83處有一主要訊號產生，表示具有零價鐵成份存在，而其比表面積經測量後為53.4 m2/g。利用ESCA分析PEI/ZVIN表面成份，結果顯示Fe/O比例為0.39，並含有Fe3O4和FeSO4等訊號在PEI/ZVIN上。
將懸浮ZVIN溶液，嘗試利用直接注入法應用於現址受污染場址試驗中，於注入後場址內各井位後，7種主要DNAPL污染物濃度均呈現明顯降低的趨勢。此外，於實驗室中利用懸浮ZVIN溶液與各井污染地下水體模擬現址降解反應，由其測試之結果與地下水管制項目及管制標準比較後，7種主要有機污染物其濃度經處理1天後濃度也大幅降低，甚至低於飲用水管制標準值，其結果與現地場址試驗結果相符，可見懸浮ZVIN溶液隨著地下水流動至污染物殘留層，將DNAPLs污染物還原成無毒害之產物。由ZVIN處理各井位抽取污染水樣試驗後之FE-SEM及TEM分析，ZVIN與PEI/ZVIN反應後其粒徑大小分別為30~150 nm及20~80 nm之間，表示ZVIN反應後聚集較為明顯。XRD、ESCA及同步輻射結構分析中，ZVIN或PEI/ZVIN與污染水樣反應一天後均氧化為Fe3O4。
利用RPI來探測懸浮ZVIN溶液注入後之趨勢變化，測線1之水平距離50 m附近的抽水井抽水量多，使得懸浮ZVIN溶液投入地下水中後有向南移的傾向，再結合採樣結果及電阻率圖的分析，可知藥劑已進入含水層使其的電性產生變化，而水平距離30~50 m處之高電阻，疑似為懸浮ZVIN溶液與污染物反應後造成。測線2之水平距離40及50 m分別經過兩口抽水井，因此測線2受到抽水的影響較測線1更為明顯，使得藥劑投入水中後有向南移甚至向東西方擴散的傾向，而測線水平距離22~42 m處之高電阻率集中區之電阻率有微幅上升的傾向，造成電阻率微幅上揚的可能原因是懸浮ZVIN溶液與污染物反應後產生Fe3O4所致。
ZVIN或PEI/ZVIN與3種含氯有機物水溶液反應一天後，由FE-SEM及TEM分析，ZVIN反應後聚集嚴重粒徑在30~150 nm間；而PEI/ZVIN反應後仍維持分散效果聚集不明顯，粒徑在20~80 nm間。由XRD及ESCA分析結果顯示，2種ZVIN均發生氧化反應，產物經與資料庫比對後以Fe3O4為主，此結果與處理各井位抽取污染水樣試驗結果相符合。此外，ZVIN與PEI/ZVIN降解3種含氯有機物水溶液實驗結果，2種ZVIN皆可降解3種含氯有機物水溶液且去除率可達99%，此結果與處理各井位抽取污染水樣試驗結果相符合。降解3種含氯有機物水溶液實驗中，0~120 min時ZVIN降解速率比PEI/ZVIN來的快，而最終效果PEI/ZVIN比ZVIN佳，可能是因ZVIN容易團聚而逐漸降低降解效果。而3種含氯有機物水溶液相同濃度下降解速率以1,2-DCE最快，TCE其次，PCE最慢。

關鍵字

奈米零價鐵微粒 ； 表面包覆 ； 聚乙基亞胺 ； DNAPLs ； 現地場址整治 ； 污染地下水體 ； 地電阻顯影儀

並列摘要

In Taiwan, remediation of sites contaminated by dense non-aqueous phase liquids (DNAPLs), especially chlorinated organic compounds, is a significantly priority in the environmental field because of their widespread use in many applications. Therefore, the main objectives of the present study were to prepare surface-modified zero-valent iron nanoparticles (ZVIN) by coating polyethyleneimine (PEI) nanofilms and in-situ DNAPLs-contaminated groundwater remediation. Characterization of ZVIN or PEI/ZVIN reacted with DNAPLs-polluted groundwater were also investigated by field emission-scanning electron microscopy (FE-SEM), X-ray powder diffractometer (XRD), transmission electron microscopy (TEM), electron spectroscopy for chemical analysis (ESCA) and resistivity image profiling (RPI). In addition, field tests of this study were also carried out to provide information concerning the removal efficiencies and feasibilities in the chemical reductive treatment processes for DNAPLs contaminated sites, and determined if further developments would be warranted.
By FE-SEM and TEM analyses, spherical ZVIN with a diameter of 20-120 nm were measured. ZVIN having a strong characteristic peak at 2θ = 44.59 was investigated by XRD patterns. The specific surface area of ZVIN measured by BET isotherms is 34.7 m2/g. From ESCA spectra, the proportion of Fe/O is 1.33 on ZVIN surface including the main species of FeO, Fe3O4, and FeSO4. In addition, ZVIN coated with PEI (PEI/ZVIN) in the form of spherical particles with a diameter of 20-80 nm were also measured by FE-SEM and TEM microphotos. PEI/ZVIN has a strong characteristic peak of Fe(0) at 2θ = 44.83 identified by XRD patterns and surface area of 53.4 m2/g measured by BET isotherms was also investigated. From ESCA spectra, the proportion of Fe/O is 0.39 on PEI/ZVIN surface including the main species of Fe3O4 and FeSO4.
After directly injecting PEI/ZVIN into the contaminated plumes, the concentrations of the seven main DNAPLs were decreased obviously. Similarly, by using PEI/ZVIN reacted with real sampling groundwater, the concentrations of the seven main DNAPLs in contaminated plumes were much lower than the concentrations before degrading. The lab-test results were similar to the data of in-situ remediation and it indicated that the PEI/ZVIN were flowing with groundwater to the contaminated plumes and reduced the DNAPLs to nontoxic compounds. By FE-SEM and TEM analyses, ZVIN and PEI/ZVIN with a diameter of 30-150 nm and 20-80 nm were measured, respectively. In addition, by using resistivity image profiling (RPI) technique, the conductivity data of suspended PEI/ZVIN solution and sampling groundwater were similar. It indicated that the combinative technology of floating surface-modified ZVIN and RPI technique would be economically and environmentally attractive for DNAPLs decontamination.
By using FE-SEM and TEM analyses, ZVIN and PEI/ZVIN reacted with TCE, PCE, and 1,2-DCE solutions having a diameter of 30-150 and 20-80 nm are measured, respectively. Surface properties of TCE, PCE, and 1,2-DCE reduced by ZVIN and PEI/ZVIN were measured by ESCA technique. The main species on ZVIN and PEI/ZVIN are FeO, Fe3O4, and FeSO4. These results indicated that the ZVIN and PEI/ZVIN can convert 99% of TCE, PCE, and 1,2-DCE solutions to nontoxic compounds. In the first two hours, the reduction rate of ZVIN was faster than PEI/ZVIN. On the contrary, since serious coagulation of ZVIN, the efficiency of PEI/ZVIN was higher that the one of ZVIN. In addition, the reduction rates of Cl-DNAPLs were 1,2-DCE > TCE > PCE solution.

並列關鍵字

Dense non-aqueous phase liquids ； Zero-valent iron nanoparticle ； Resistivity image profiling ； Surface-modification ； Polyethyleneimine ； In-situ contaminated groundwater remediation

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