EPA-100-U1L1-02-101

100

1,800 千元

2011/06/30

2011/12/31

董瑞安

永續發展室(停用)

蘇鈺珊

清華大學

廢棄物管理

金-磁鐵礦(Au-Fe3O4);奈米催化劑;類芬頓反應;異核結構奈米材料;硝基酚;氯酚

Gold-magnetite;nanocatalysts;fenton-like reaction;heterostructured nanocrystals;nitrophenols;chlorophenols

董瑞安

03-5715131#35569

radoong@mx.nthu.edu.tw

本研究的主要目的在於藉由金與磁鐵礦奈米材料的製備與合成，配製成具有高催化特性及回收再利用的多功能性Au-Fe3O4異核結構奈米複合材料，並將之應用於水體環境中的難分解有機污染物催化處理，同時探討此異核結構材料在不同水體環境中的催化與回收再利用特性。研究結果發現利用異丁基胺硼烷綜合物作為還原劑，於不同溫度下(2-20oC)進行氯金酸還原反應，可成功製備顆粒大小由4到7nm的金奈米粒子，而利用相同的熱分解法可成功製備金-磁鐵礦異核結構，藉由改變金奈米粒子的尺寸，可合成啞鈴形與花朵形的金-磁鐵礦異核結構，並應用於4-硝基酚與2,4-二硝基酚的還原催化反應。研究結果發現，所製備出的金-磁鐵礦異核結構具有良好的磁性與催化特性，然而，由於啞鈴形與花朵形金-磁鐵礦異核結構間的磊晶成長方式不同，導致其在磁性與催化活性上有所不同。以啞鈴形金-磁鐵礦異核結構而言，其對硝基酚化合物擬一階反應速率常數為0.63-0.72 min-1，而對於花朵形奈米粒子而言，其擬一階反應速率常數為0.38-0.46 min-1。此外，啞鈴形金-磁鐵礦異核結構材料對硝基酚類化合物之還原反應速率符合 Langmuir-Hinshelwood動力學模式，催化還原反應的活化能為26.3 kJ mol-1，反應速率常數則隨pH值的增加而降低。另在添加雙氧水的酸性環境中，約有40% 的亞鐵離子釋出於水溶液中，可進行異相芬頓反應有效去除氯酚類化合物及胺基酚，其反應效率受到所溶出亞鐵離子總量、pH值及雙氧水濃度影響，另所製備而得的奈米粒子具有磁性回收能力及高達6次以上的再使用率，也能維持顆粒形貌完整性與結晶性。同時，連續式反應器結果顯示，Au-Fe3O4 異核結構材料在連續式反應器中對硝基酚及氯酚類化合物仍具有相當優異的處理效能。本計畫的結果顯示所開發的金-磁鐵礦異核結構材料具有獨特的物化特性，不僅為環境友善製程，兼具回收再利用及且不產生對環境有危害之終產物，操作成本也優於達相同處理效能之高級氧化處理技術，同時可應用於不同的異相催化反應及其他污染物，實為一相當值得開發應用的綠色奈米科技。

金-磁鐵礦(Au-Fe3O4);奈米催化劑;類芬頓反應;異核結構奈米材料;硝基酚;氯酚

期末正式報_final.pdf

5MB

2012/3/1 上午 12:00:00

The main purpose of this study is to synthesize monodispserse Au-Fe3O4 heterostructures with excellent catalytic properties, recyclability and reusability for effective decomposition of emerging pollutants in the environment. The catalytic efficiency and reusability under different environmental condition were also evaluated in this study. TEM results show that different sizes of monodisperse Au nanoparticles (NPs) at 4-7 nm were successfully synthesized by injecting tert-butylamine borane complex to a mixture containing HAuCl4∙3H2O, oleylamine (OAm) and cyclohexane at different reaction temperatures (2-20oC). The monodisperse and size-tunable magnetic iron oxide nanoparticles were also successfully synthesized via thermal decomposition method. The diameters of as-synthesized Fe3O4 NPs decrease upon increasing the concentrations of iron oleate complex and oleic acid/oleylamine. In addition, size-dependent crystallinity and magnetic property of iron oxide NPs are presented. It is found that larger Fe3O4 NPs have a higher degree of crystallinity and saturation magnetization. More importantly, Au-Fe3O4 heterostructures are successfully fabricated by using the same synthesis procedure. The dumbbell- and flower-like Au-Fe3O4 heterostructures have been successfully fabricated using different sizes of Au NPs as the seeds for magnetically recyclable catalysis of p-nitrophenol and 2,4-dinitrophenol reduction. The heterostructures exhibit bifunctional properties with high magnetization and excellent catalytic activity towards nitrophenol reduction. The epitaxial linkages in dumbbell- and flower-like heterostructures are different, leading to the change in magnetic and catalytic properties of the heterostructured nanocatalysts. The pseudo-first-order rate constants for nitrophenol reduction are 0.63-0.72 min-1 and 0.38-0.46 min-1 for dumbbell- and flower-like Au-Fe3O4 heterostructures, respectively. In addition, the reduction of nitrophenol by Au-Fe3O4 is a surface-mediated reaction and followed Langmuir-Hinshelwood kinetics with the activation energy of 26.3 KJ mol-1. In the acidic solution at pH 3, 40% of ferrous ions will released from magnetite and then react with hydrogen peroxide to form heterogeneous Fenton system for decomposition of chlorophenols and aminophenol. In addition, the heterostructured nanocatalysts show good separation ability and reusability which can be repeatedly applied for nearly complete reduction of nitrophenols for at least 6 successive cycles and the morphology as well as the crystallinity can be maintained after Fenton-like reaction. The continuous test clearly showed that the nanomaterial developed in this study is cost benefit. These unique properties make Au-Fe3O4 heterostructures an ideal platform to study various heterogeneous catalytic processes. In addition, the fabrication procedure for Au-Fe3O4 is environmentally friendly and the as-synthesized heterostructures can be recycled and reused for effective decomposition of nitrophenols and chlorophenols into harmless end-products, clearly showing that the synthesis process developed in this study is a green nanotechnology.

Gold-magnetite;nanocatalysts;fenton-like reaction;heterostructured nanocrystals;nitrophenols;chlorophenols