電解加強分散性奈米鈀鐵複合金屬反應牆整治地下水中四氯乙烯之研究

Remediation of Tetrachloroethylene in Groundwater by Dispersed Bimetallic Palladium-Iron Reactive Barrier Enhanced by Electrolysis

陳信憲(Shin-Shian Chen)

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/博士(2014年)

https://doi.org/10.6346/NPUST.2014.00034

摘要

含氯有機化合物一般多屬於重質非水相液體(dense non-aqueous phase liquids; DNAPLs)，如四氯乙烯(tetrachloroethylene; PCE)，其性質難溶於水、比重較水大、具有低黏滯性、低可燃性、高揮發性以及化學性質安定等特性，因此在工業上廣泛被應用，其用途多做為溶劑或合成製造產品的原料使用。含氯溶劑大多具有毒性或致癌性等危害性質，由於此類化合物具有脂溶性及易揮發等性質，與人體接觸可經由皮膚、呼吸道及消化道進入體內，引起健康危害，世界各國多已將其列為毒性污染物質，依據其危害性質加以管制。
本研究之主要目的是希望利用複合金屬反應牆還原脫氯整治方法發展出一套令人滿意的地下水中含氯有機污染物整治復育系統。在本研究中自行合成奈米鈀鐵(Pd/Fe)微粒，並利用羧甲基纖維素 (carboxymethyl cellulose; CMC)作為分散劑，以兩種不同方法配置分散性奈米Pd/Fe懸浮劑，用以進行PCE之批次及砂箱降解試驗。批次試驗在一容量為1 L之反應瓶內進行，依批次試驗結果顯示奈米Pd/Fe可以有效地降解水中PCE，添加越多量Pd/Fe之批次試驗，其PCE被降解的時間越快，而其kobs也越大。不同反應溫度降解批次試驗結果顯示，反應溫度越高，PCE被降解的速率也越快，且反應溫度越高時，其kobs與kSA值也越大。由添加CMC作為奈米Pd/Fe之分散劑降解試驗的結果顯示，當加入1 g分散性奈米Pd/Fe即可與加入5 g 非分散性奈米Pd/Fe有相當之降解效能，且添加分散劑之奈米Pd/Fe實驗所得之kSA值為非分散性奈米Pd/Fe實驗之4倍。砂箱試驗在一長130 cm 、寬10 cm、高20 cm 之玻璃材質箱內進行，由砂箱降解試驗結果顯示，二種分散性奈米Pd/Fe懸浮液反應牆都可有效降解地下水中的PCE，其中以第一種方法備製(在奈米Pd/Fe合成過程加入分散劑)之分散性奈米Pd/Fe懸浮液降解效能較第二種方法(奈米Pd/Fe合成後再加入分散劑)為佳。而結合電解反應則可以有效地延長Pd/Fe的反應活性時間，並可將已失去反應活性的Pd/Fe再度活化。在批次及砂箱降解試驗過程中皆未發現PCE降解可能產生的含氯副產物，因在批次試驗中可以得到很高的氯離子回收率，說明PCE應是被Pd/Fe完全脫氯降解。本研究所獲得之成果可提供受含氯有機化合物污染場址復育之參考及選擇。

關鍵字

四氯乙烯 ； 雙金屬 ； 分散劑 ； 脫氯反應 ； 電解 ； 反應牆 ； HASH(0x1850bfc0)

並列摘要

Chlorinated organic solvents are widely used in industry, mainly as solvents and raw materials in the manufacture of commodity chemicals. Most of chlorinated solvents such as tetrachloroethylene (PCE) belong to Dense Non-Aqueous Phase Liquids (DNAPLs), with the properties of low solubility in water, denser than water, low viscosity, low flammability, high evaporability, and stable chemical property. Many kinds of chlorinated solvents had been recognized as carcinogens and/or toxins to human being, and they are resistant to degrade in environment that causes great impacts to groundwater resources. For their toxicity and strong bioaccumulation potential, chlorinated solvents are regarded as the pollutants that must be prior treated in many countries.
The purpose of this study is to develop a bimetallic reactive barrier system for the remediation of groundwater contaminated by chlorinated solvents. Nanoscale palladized-iron (Pd/Fe) bimetallic particles and two kinds of dispersed Pd/Fe suspensions, using carboxymethyl cellulose (CMC) as dispersant, were synthesized and utilized to react with PCE to investigate their degradation capability. Batch tests were proceeded in a 1,000 mL reaction bottle. The results showed that the kobs increased with the amount of Pd/Fe addition. The kobs and kSA increased as the reaction temperature was raised from 20 to 40C. CMC enhanced the kSA values of Pd/Fe particles to PCE degradation about 4 times. The sandbox experiments were performed in a 130 x 10 x 20 cm (length x width x height) glass box. Two kinds of nanoscale dispersed Pd/Fe suspensions were added into the permeable reactive barrier individually to degradate the PCE in aquifer. The results showed that PCE degradation ability of the first-kind dispersed Pd/Fe suspension (CMC was added during the synthesis process of Pd/Fe particles) was better than the second one (CMC was added after Pd/Fe particles were synthesized). Besides, when the electrolysis was integrated with the permeable reactive barrier packed with Pd/Fe particles, the active period of Pd/Fe particles could be extended. No potential chlorinated byproducts including trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), cis-1,2-dichloroethylene (cis-1,2-DCE), tran-1,2-dichloroethylene (tran-1,2-DCE), and vinyl chloride (VC) were detected in the batch and sandbox experiments. Because of the high recovery rate of Cl- in the batch tests, PCE must be completely dechlorinated by Pd/Fe particles. The results of this study may provide a useful alternative method for the in-situ remediation of chlorinated solvents.

並列關鍵字

Tetrachloroethylene ； PCE ； Bimetallic ； Dispersant ； Dechlorination ； Electrolysis ； Reactive barrier

參考文獻

行政院環境保護署網站 http://www.epa.gov.tw/

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