利用表面改質奈米零價鐵還原降解高能火炸藥TNT、RDX 及HMX 污染地下水整治工程技術之研發及評估

本研究中合成之表面改質奈米零價鐵(nZVI) 乃於氬氣下經燈罩法烘乾並惰化後而得，由FESEM分析其粒徑為50 ~ 80 nm，BET 量測其比表面積為42.557 m^2/g。在降解實驗中，以0.1 g 之nZVI 降解3 種高能火炸藥水溶液，結果顯示在室溫下(25 ± 1°C) 於1 h 內可完全降解90 ppm 之TNT、35 ppm 之RDX 及5 ppm 之HMX。在動力學研究中，將nZVI 降解3 種不同濃度高能火炸藥實驗結果代入簡化的L-H 動力學模式計算得到其降解反應為一階反應。另以3 種不同的高能火炸藥於25°C 及35°C 的溫度下進行實驗，並以Arrhenius equation 計算得到TNT、RDX 及HMX的活化能分別為9.7、10.1 及12.5 kcal/mol。由LC/MS/MS 及GC/MS 分析結果顯示高能火炸藥反應途徑是第一步為NO_2 官能基團被還原取代成NO 官能基團，第二步為NO 官能基團被還原取代成NH_2 官能基團後，導致結構不穩定而水解開環。分析與高能火炸藥反應前後之nZVI，由FESEM及TEM 分析發現有nZVI 數量減少及片狀產物的增加的趨勢，再以XPS 分析顯示其表面具有Fe、FeO、Fe_3O_4、及Fe_2O_3 等四種不同的氧化物，且其反應趨勢為Fe(0) → FeO → Fe_3O_4 →Fe_2O_3。以XANES 分析結果顯示，其反曲點為Fe3O4，且由EXAFS 分析其中心Fe 原子配位數接近4，表示結構可能是八面體中平面四邊形結構；Fe-O 鍵距約為1.94 ± 0.01 Å，搭配XRD 分析其結果類似Fe_3O_4 及Fe_2O_3。本文亦說明利用nZVI 來整治受高能火炸藥污染之土壤及地下水之復育工程設計與模擬測試之成果。

關鍵字

奈米零價鐵；高能火炸藥；還原降解；表面改質；地下水污染場址整治

並列摘要

By using flowing Ar inertial method, surface-modified zero-valent iron nanoparticles (nZVI) with a diameter of 50 ~ 80 nm and specific surface area of 42.56 m^2/g were examined by FE-SEM and BET. The XRD patterns show that nZVI have a strong characteristic peak at 2θ = 44.6°. In the experiments, 90 ppm TNT, 35 ppm RDX, and 5 ppm HMX were degraded completely with 0.1 g nZVI in 1 h at room temperature (25 ± 1°C). The experimental results were simulated using a simple Langmuir-Hinshelwood equation, and the degradation statistics corresponded to the pseudo first order kinetics. A thermodynamic study was carried on three different high-explosives with a temperature range of 25 ~ 35°C, and the activation energies of TNT, RDX, and HMX were calculated as 9.7, 10.1, and 12.5 kcal/mol by the Arrhenius equation, respectively. In the investigation of degradation pathways, the intermediates were identified by LC/MS/MS and GC/MS. The substitution of high-energy explosives was reduced by different quantities of the nitroso group into hydroxylamine. The ring structures of the explosives were destabilized when the nitroso group was further reduced to a hydroxylamine group, eventually resulting in a ring cleavage reaction by a hydrolysis route. In reductive degradation processing, the nZVIs were reduced and sheet-type materials were also found. Meanwhile, the surfaces containing Fe, FeO, Fe_3O_4, and Fe_2O_3 were examined by XPS, and the crystalline structures that were found were similar to the Fe_3O_4 and Fe_2O_3 identified in the XRD patterns. In addition, the valence of nZVI after degradation was 8/3, as shown by XANES. The coordination number of the Fe atoms was close to 4, and the bond distance of Fe-O was about 1.94 ± 0.01 A, as determined by the EXAFS spectra. This study also discusses the issues of remediation engineering and simulates the basic design of nZVI reactive permeable barriers for TNT/RDX/HMX contaminated soils and ground waters.

並列關鍵字

zero-valent iron nanoparticle ； high-energy explosives ； reductive degradation ； surface modification ； contaminated groundwater site remediation

國際替代計量

利用表面改質奈米零價鐵還原降解高能火炸藥TNT、RDX 及HMX 污染地下水整治工程技術之研發及評估

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