疏水性奈米鐵懸浮液與非水溶液相三氯乙烯之反應性

重質非水相液體(DNAPL)是整治土壤地下水時面臨的最棘手問題。因DNAPL物化性質特殊與傳輸性質複雜，難以掌握污染源位置，去除不易。近年來，以奈米零價鐵應用於土壤地下水整治之研究逐漸增多。過去研究奈米鐵降解含氯碳氫化合物之反應，多在水相中進行，對於油性之殘餘相及DNAPL蓄積池之處理有限。因此本研究針對油相之污染物，探討以不同奈米零價鐵劑量及不同含水率下降解三氯乙烯之反應速率。最後設計一管柱模擬試驗，評估未來以疏水性奈米懸浮液在現地使用之可行性。本研究以聚丙烯酸(PAA)作為分散劑合成奈米零價鐵，再以聚甲基丙烯酸甲酯(PMMA)做為表面修飾劑，使其成為疏水性奈米鐵，並探討其性質及其對油相三氯乙烯之反應效能。又製備重質非水相奈米顆粒懸浮液，係選用碳酸二甲酯做為承載液，模擬DNAPL之特性，與三氯乙烯進行反應。研究結果顯示，溫度控制在60℃及起始劑-偶氮二異丁腈(Azobisisobutyronitrile, AIBN)濃度在0.5%下，對奈米零價鐵進行表面改質，所得疏水性奈米鐵在碳酸二甲酯中懸浮效果較佳。改質後之奈米鐵平均粒徑約在50-100 nm，比表面積約為40 m2/g。 25 mL油相中0.25g疏水性奈米零價鐵降解三氯乙烯於不含水、含水率濃度2M及含水率濃度4M之比表面積基準化擬一階反應動力速率常數(kSA)分別為 1.58×〖10〗^(-5), 1.43×〖10〗^(-5), 1.15×〖10〗^(-5), h-1•L-1•m-2。結果顯示在低濃度的三氯乙烯下，相同奈米鐵於不同含水率下，降解三氯乙烯沒有明顯差異，且氫氣的產生不會影響三氯乙烯的降解。管柱模擬試驗中，在水飽和之石英砂層中注入之重量�濃度為0.146 g/100 μL 之純液態三氯乙烯，再以含有零價奈米鐵0.3g 之25mL 疏水性懸浮液注入管柱中，靜置六天後所得，空白實驗組殘留率為78.14%，實驗組為43.9%。顯示疏水性奈米零價鐵懸浮液，在多孔隙介質中移動時，能與油相之三氯乙烯混合產生降解反應。

關鍵字

表面改質；聚甲基丙烯酸甲酯；三氯乙烯；重質非水相奈米零價鐵懸浮液；疏水性奈米鐵顆粒；多孔介質

並列摘要

The remediation for dense non-aqueous phase liquids (DNAPLs) in soils and aquifers is the most difficult task at present, due to the complex nature of the transport of DNAPL, special physical and chemical properties, and difficulty to detect and characterize these kind of pollution sources.. In recent years, the application of nano-scale zero-valent iron (NZVI) in soil and groundwater treatment is given increasing attention. The experiments of the reaction of chlorinated aliphatic hydrocarbons with NZVI were mostly conducted in aqueous phase instead of in non-aqueous phase. The helps to the remediation of the residual zone and DNAPL pools are limited. Therefore, the purposes of this research are to investigate the rates of trichloroethene (TCE) reduction under different dosages of NZVI with different water content and to design a column experiment to see the feasibility of application of the non-aqueous phase NZVI in ground water aquifers to remove DNAPL of chlorinated hydrocarbons. Poly acrylic acid (PAA) was applied as the dispersant to produce NZVI, and then poly methyl methacrylate (PMMA) was synthesized on particle suspension as surface modifier to produce hydrophobic zero-valent iron (HZVI). The properties of the HZVI and its capability of degrading of TCE in oil phase were examined. Dimethyl carbonate (DMC) was chosen as the carrying liquid to prepare the dense non-aqueous nano-scale iron particle suspension. The results showed that the stability of the hydrophobic nano-iron suspended in dimethyl carbonate was the best when the NZVI was modified under conditions of temperature at 60 ℃ and the concentration of initiator, azobisisobutyronitrile (AIBN), at 0.5% in the solution. The particle size ranged from 50 to 100 nm, surface area was 40 m2/g. The rate of the reduction of trichloroethene (TCE) in non-aqueous phase by HZVI can be explained by first-order reaction kinetics. The surface specific rate constants under water-free, moisture content of 2M and moisture content of 4M are 1.58×〖10〗^(-5), 1.43×〖10〗^(-5), 1.15×〖10〗^(-5), h-1•L-1•m-2, respectively. No significant difference in the degradation of TCE was observed at low TCE concentrations, for different moisture contents. The generation of hydrogen gas did not affect the degradation of TCE. The recovery of total TCE was 78.14%, and 43.9% for the controlled and HZVI treatment column experiments. The results showed that HZVI in oil phase in porous media will be mixed with non-aqueous TCE phase to some extent and reduce significant amount of TCE.

並列關鍵字

surface modification ； poly methyl methacrylate ； dense nonaqueous suspension of nano scale zero valent iron ； trichloroethene ； hydrophobic nano particles ； porous media.

參考文獻

行政院環境保護署，2000，土壤汙染評估技術規範之研究計畫。

劉佩格，製備環境復育用之重質非水相奈米零價鐵懸浮液，國立台灣大學環境工程學研究所碩士論文，2010.

林弘偉，合成重質非水相奈米零價鐵懸浮液之研究，國立台灣大學環境工程學研究所碩士論文，2011.

張晏禎，不同奈米零價鐵與油相液體中三氯乙烯之反應性，國立台灣大學環境工程學研究所碩士論文，2012.

Berge, N. D., Ramsburg, C. A. 2009. Oil-in-water emulsions for encapsulated delivery of reactive iron particles. Environ. Sci. Technol 43 (13):5060-5066.

國際替代計量

疏水性奈米鐵懸浮液與非水溶液相三氯乙烯之反應性

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