奈米零價鐵降解受TNT、RDX及HMX高能火炸藥污染水體之研究

Decontamination of TNT, RDX, and HMX High-Eexplosive Wastewaters by Zero-Valent Iron Nanoparticles

謝明君(Ming-June Hsieh)

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.2007.00277

摘要

由於高能火炸藥(TNT、RDX及HMX)製程中任意排放於環境中廢水，常常造成土壤及地下水的污染，此污染物對人體具高毒性且難以從環境中移除，因此，環保且有效的處理受高能火炸藥污染的水體的技術，即成為現今研究之重要課題。本研究之主要目為利用化學還原法製備奈米零價鐵顆粒(nano-Fe(0))，處理受高能火炸藥污染的水體。研究內容可區分為兩部分，第一部份以高效能液相層析儀(HPLC)、液相層析串聯質譜儀(LC/MS/MS)及氣相層析質譜儀(GC/MS)，探討受污染水體中高能火炸藥之降解效率、反應動力參數、熱力學模式及反應途徑；第二部份則使用場發掃描式電子顯微鏡(FE-SEM)、X光粉末繞射儀(XRPD)、化學分析電子光譜儀(ESCA)、穿透式電子顯微鏡(TEM)、BET比表面積測定儀(BET)及同步輻射(XANES/EXAFS)分析鑑定nano-Fe(0)反應前後結構特性及產物之差異性，進而深入瞭解nano-Fe(0)還原降解反應高能火炸藥(TNT、RDX及HMX)之機制及途徑。
本論文中合成之nano-Fe(0)實驗乃於氬氣下經燈罩法烘乾並惰化後XRD圖譜文獻資料相符。由FE-SEM分析其粒徑為20~50 nm，BET量測其比表面積為42.557 m2 g-1。降解研究中，以0.1 g之nano-Fe(0)降解3種高能火炸藥水溶液，實驗結果顯示在室溫下(25 ± 1℃)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nano-Fe(0)降解三種不同濃度高能火炸藥實驗結果代入簡化的Langmuir-Hinshelwood動力學模式ln(C0/Ca) = kt計算得到R Square > 0.995，其降解反應為一階反應。在熱力學模式研究中，則是以三種不同的高能火炸藥於25及35℃的溫度下進行實驗，並以Arrhenius equation計算其活化能，得到TNT、RDX及HMX的活化能分別為9.743、10.079及12.460 kcal mol-1。在反應途徑研究中，由LC/MS/MS及GC/MS分析結果顯示高能火炸藥反應反應途徑是第一步為NO2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NH2官能基團後，導致結構不穩定而水解開環。
分析nano-Fe(0)與高能火炸藥反應前中後之產物，由FE-SEM及TEM分析發現有nano-Fe(0)顆粒數量減少及片狀產物的增加的趨勢，再以ESCA分析顯示其表面具有Fe、FeO、Fe3O4、及Fe2O3等四種不同的氧化物，且其反應趨勢為Fe(0) → FeO → Fe3O4 → Fe2O3。
nano-Fe(0)與高能火炸藥反應後最終產物，以X光吸收近邊緣結構(XANES)分析結果顯示，其反曲點最接近Fe3O4，且藉由延伸X光吸收細微結構（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的鍵距約為1.94 ± 0.01 Å，再以XRPD分析晶形結構，其圖譜結果發現相似Fe3O4及Fe2O3。

關鍵字

奈米零價鐵 ； 高能火炸藥 ； TNT ； RDX ； HMX ； 還原降解 ； 同步輻射光譜

並列摘要

Currently, soil and groundwater were polluted by explosives-contaminated wastewaters discharged from military factory worldwide. These high-explosives are toxic to human beings and very difficult to be removed from the environment. Therefore, a highly efficient and clean method was developed utilizing zero-valent iron nanoparticles to reduce the explosives-contaminated wastewaters. In this research, HPLC, LC/MS/MS, and GC/MS were used to determine the efficiency of degradation, kinetic model, thermal model, activation energy, and reaction pathways. Moreover, the properties of zero-valent iron nanoparticles after degradation were also analyzed by FE-SEM, TEM, XRPD, ESCA, BET, and XANES/EXAFS techniques.
In this study, zero-valent iron nanoparticles with a diameter of 20-50 nm and specific surface area of 42.557 m2?eg-1 were measured by FE-SEM and BET. Zero-valent iron nanoparticles had a strong characteristic peak at 2θ = 44.6o were investigated by XRPD patterns. In the degrading experiments, 90 ppm TNT, 35 ppm RDX and 5 ppm HMX at room temperature (25 ± 1℃) were degraded completely with 0.1 g zero-valent iron nanoparticles in 1 h. The experimental results were placed into a simple Langmuir-Hinshelwood equation (ln(C0/Ca) = kt) and the R-squares were all upon 0.995. However, the degradation statistics corresponded to the pseudo first order kinetics. The thermodynamics study was carried on three different high-explosives under 25-35℃ and the activation energies of TNT, RDX, and HMX were calculated to 9.743, 10.079, and 12.460 kcal?emol-1 by Arrhenius equation, respectively.
In the investigation of degradation pathway, the intermediates were identified by LC/MS/MS, and GC/MS. The substitution of high-explosives was reduced by different quantities of nitroso group into hydroxylamine. The ring structure of the explosives became destabilized when nitroso group was further reduced to a hydroxylamine group resulting into ring cleavage by a hydrolysis route eventually.
In reductive degradation processing, the zero-valent iron nanoparticles were reduced and also sheet-type materials were produced. Meanwhile, the surface of Fe, FeO, Fe3O4, and Fe2O3 was measured by ESCA and the crystalline structures were similar with Fe3O4 and Fe2O3 identified by XRPD patterns. In addition, the valence of zero-valent iron nanoparticles after degradation was 8/3 as shown by XANES technique. The coordination numbers of Fe atom were close to 4 and the bound distance of Fe-O was about 1.94 ± 0.01 Å as determined by EXAFS spectra.

並列關鍵字

ero-valent iron nanoparticle, High-explosives, TNT ； RDX ； HMX ； Reductive degradation ； XANES/EXAFS.

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