以單壁奈米碳管吸附芳香族化合物吸附機制之探討

Adsorption of Aromatic Compounds on SWCNTs

蔡涵哲(Hen-je Tsai)

指導教授 ： 秦靜如

國立中央大學/工學院/環境工程研究所/碩士(2007年)

摘要

本實驗主要利用帶有不同官能基之吸附質，苯、甲苯及氯苯進行吸附實驗，探討奈米碳管和芳香族化合物間的吸附機制。酸氧化奈米碳管所引進之含氧官能基產生吸附空間上的障礙，降低吸附能力，且影響的程度與苯環上取代基的大小成正比，奈米碳管本身對三種吸附質的吸附能力與吸附質的水溶解度相關，另外也受吸附質苯環上取代基的影響；在不同的pH值下進行吸附實驗，發現未受酸氧化的奈米碳管的吸附行為較不受pH的影響，推測主要的反應機制還是以苯環與碳環的π-π鍵為主，而利用酸氧化過後的碳管吸附時，苯在高pH值時會因水簇現象降低吸附的能力，甲苯則會因為推電子烷基使烷基上的氫趨向H+的形式，與高pH值下離子化的含氧官能基進行吸引，提高吸附能力，而氯苯則利用氯上的孤電子對與苯環進行共振，使π-π鍵的效應增強成為主要的鍵結反應，因此不受pH值的影響，最後在熱力學上的探討，苯的吸附能力會隨著溫度的提高而降低，再經過熱力常數的計算，得到苯的吸附反應為放熱且自發性的反應。

關鍵字

芳香族化合物 ； 吸附 ； 奈米碳管

並列摘要

The adsorption mechanisms for benzene, toluene, and chlorobenzene by SWCNTs before and after acid oxidation were discussed in this study. The influences of the functional groups of SWCNTs were studied by acid-oxidized SWCNTs. The adsorption capacity for benzene, toluene, and chlorobenzen are affected by solubility and the functional groups of adsorbates. The oxygen-containing surface groups introduced by acid oxidation cause the steric obstruction and the decrease in adsorption capacity. The adsorption of benzene, toluene, and chlorobenzene by the raw SWCNTs at different solution pH values is slightly affected by solution pH in the range of 3-11, which suggest the π-π interaction is the dominant interaction. The oxygen-containing surface groups introduced onto SWCNTs by acid oxidation result in water clustering at high pH and decrease in the adsorption capacity for benzene. For the adsorption of toluene, an attraction which is similar to hydrogen bonding between H+ of the methyl group and the oxygen-containing surface groups is introduced. The π-π interaction between the bigger resonance structure of chlorobenzene and the C-ring of graphene sheet of SWCNTs is the dominant interaction in adsorption of chlorobenzene, which affects the adsorption at different solution pH slightly. Finally, the adsorption capacity for benzene increases with increasing temperature and the thermodynamic parameters indicate the adsorption of benzene is an exothermic and spontaneous reaction.

並列關鍵字

carbon nanotubes ； aromatic compounds ； adsorption

參考文獻

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