電解加強奈米鈀/鐵雙金屬粒子滲透性反應牆處理地下水中四氯乙烯之研究

Electrolysis-Enhanced Permeable Reactive Barrier Packed with Nano-Pd/Fe Bimetallic Particles of Perchloroethylene

林明憙(Ming-Hei Lin)

指導教授 ： 黃益助

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2012年)

https://doi.org/10.6346/NPUST.2012.00267

摘要

本研究以四氯乙烯(PCE)作為地下水污染整治之主要標的污染物，探討電解作用對奈米鈀鐵反應牆處理地下水中PCE處理效率之影響。實驗架構分為四個階段，第一階段為石英砂及奈米鈀鐵基本特性分析，第二階段為不同pH值(pH 8-9)對奈米鈀鐵雙金屬降解PCE影響之批次試驗，第三階段為多孔介質傳輸之砂箱試驗，第四階段為處理前、後奈米鈀鐵之SEM-EDS及FTIR分析。
本研究實驗室合成奈米鈀鐵之平均粒徑為111.1 nm，比表面積為56.05 m2 g-1，由X-ray繞射儀(XRD)鑑定奈米鈀鐵，只發現Fe的吸收峰並未發現Pd，可能是Pd的添加量太低，導致Pd在XDR上偵測不到。在不同pH值降解PCE試驗中，隨著pH值的提高，奈米鈀鐵對PCE還原降解能力發生降低之情形。降解PCE所產生Cl-之理論釋出量皆接近於實際Cl-釋出量，PCE降解量和Cl-釋出量兩者之間成正相關性。本研究所有還原降解PCE之批次試驗中，皆未檢測到三氯乙烯(trichloroethylene, TCE)、1,1-二氯乙烯(1,1-dichloroethylene, 1,1-DCE)、順1,2-二氯乙烯(cis-1,2-dichloroethylene, cis-1,2-DCE)、反1,2-二氯乙烯(trans-1,2-dichloroethylene, trans-1,2-DCE)、氯乙烯(vinyl chloride, VC)等副產物。

藉由追蹤劑試驗可發現平均停留時間約為理論值的1.7倍左右，奈米鈀鐵反應牆降解PCE試驗中，奈米鈀鐵之反應活性約可維持28 hr左右，與郭(2009)與黃(2010)研究進行比較，奈米鈀鐵反應活性的持續時間明顯高於奈米零價鐵2~4倍。在實驗中，反應槽內ORP能穩定維持在-300 mV以下，顯示系統呈現穩定的還原狀態，Cl-濃度有明顯的提高，顯示奈米鈀鐵對於PCE確實有還原脫氯作用。電解加強奈米鈀鐵反應牆降解PCE試驗中，可藉由電解反應，在陽極附近釋出H+來酸洗顆粒表面的沉積物，並增加其反應活性，實驗結果顯示奈米鈀鐵對PCE不能完全降解，其反應活性約可維持在16~20 hr左右，但效果並不如預期。因此，未來電解加強奈米鈀鐵反應牆技術仍需再進一步對電流、電壓及電解液等方面進行探討，以利於應用在現地處理受含氯有機物污染地下水整治復育上。
SEM-EDS表面型態觀察中，反應前表面是以顆粒型態串聯成鏈狀之結構所組成，反應後表面呈現出不規則片狀之型態。FTIR鑑定反應後之奈米鈀鐵，在3200~3500 cm-1有一個強而廣的訊號判定為O-H，在1600~1400 cm-1間訊號有增強情形，其中，1539 cm-1有一個較強訊號判定為硝基化合物(NO2)，1385 cm-1有一個較強訊號判定為CH3，並推測可能是烷類，另外，在967 cm-1有一個較強訊號判定為烯類(C=C-H)，最後在600~800 cm-1間訊號有增強情形其判定為C-Cl。
關鍵字：四氯乙烯、奈米鈀鐵、追蹤劑、透水性反應牆、電解

關鍵字

四氯乙烯 ； 奈米鈀鐵 ； 追蹤劑 ； 透水性反應牆 ； 電解

並列摘要

The aim of this study is to investigate the degradation efficiency of target pollutant, perchloroethylene (PCE), by nano-palladium/iron (Pd/Fe) bimetallic metal particles enhanced by electrolysis. The experiments were divided into four stages. The first stage was to characterize the properties of quartz sand and nano-Pd/Fe particles. The second stage was to conduct the batch tests under various pH values (pH 8-9) on the effects of PCE degradation with nano-Pd/Fe. The third stage was to observe the transport behaviors of solutes through the porous media in a bench-scale sand box. And the fourth stage was to identify the variations of nano-Pd/Fe before and after the reaction with PCE by SEM-EDS and FTIR analysis.
The average size and specific surface area of lab-synthesized nano-Pd/Fe particles were 111.1 nm and 56.05 m2 g-1, respectively. The absorption peaks of nano-Pd/Fe analyzed by the X-ray diffraction detector (XRD) only identified Fe. That may be due to the trace amount of Pd on bimetallic metals. For the tests of various pH values (pH 8-9) on PCE degradation with nano-Pd/Fe, the efficiency decreased with higher pH values. The concentration of Cl- released from PCE degradation was close to the theoretical values. The PCE degradation levels were positive correlated with the release amounts of Cl-. In this study, the by-products of PCE degradation such as trichlorethylene (TCE), cis-1,2-dichloroethylene (cis-1,2-DCE), trans-1,2-dichloroethylene (trans-1,2-DCE), 1,1-dichloroethylene (1,1-DCE), and vinyl chloride (VC) were not detected.
Via the tracer tests, the average residence time was about 1.7 times higher than the theoretical value. For the test of permeable reactive barrier (PRB) packed with nano-Pd/Fe on PCE degradation, the duration of reactivity of nano-Pd/Fe could be maintained about 28 hr which was around 2 to 4 times higher than that of nano zero valent iron. During the tests, ORP values were steadily maintained below -300 mV in the PRB showing a reduction state was kept in the system. Dechlorination of PCE with nano-Pd/Fe particles were identified by the significant increase of Cl- concentration. The test of nano-Pd/Fe PRB enhanced by electrolysis on PCE degradation, H+ released near the anode was able to acid-washed the surface of Pd/Fe particles to increase their reactivity. The results showed that PCE was not completely degraded by the nano-Pd/Fe particles. The reactivity of Pd/Fe was observed to maintain about 16 to 20 hr. Therefore, more researches on the aspects of current, potential, and electrolyte to the performance of electrolysis enhanced PRB packed with nano-Pd/Fe technology are needs to facilitate its application to in-situ remediation of groundwater contaminated by chlorinated solvents.
From the images observed by SEM-EDS, the surface morphology of nano-Pd/Fe particles displayed chain-like structure and irregular flakes pre-reacted and post-reacted with PCE, respectively. The spectrum of fresh nano-Pd/Fe particles analyzed by FTIR showed that a strong and broad absorption signal ranged from 3200 to 3500 cm-1 was identified to be O-H and at 1539, 1385, 967 cm-1 to be the nitro compounds (NO2), alkane (CH3), and alkene (C = CH), respectively. Finally, a signal ranged from 600 to 800 cm-1 was C-Cl.
Keywords: perchloroethylene, nano-palladium/iron, tracer, permeable reactive barrier, electrolysis

並列關鍵字

perchloroethylene ； nano-palladium/iron ； tracer ； permeable reactive barrier ； electrolysis

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