多壁奈米碳管對甲苯(Toluene)蒸氣之吸附貫穿特性之研究

Abstract

Carbon nanotubes (CNTs), a new material in nanotechnology, have good physical and chemical properties with nanoscale porosity, large surface area and several excellent characteristics. It has been considered as a potential material for gas storage. If CNTs can be an effective adsorbent to adsorb gas or organic vapor, it will make a good contribution to energy storage, gas sensing and pollution prevention. Toluene is used widely in industry, but it might damage the human health when it volatiles. Therefore, this study intends to investigate the adsorption breakthrough behaviors of toluene on three kinds of multi-walled carbon nanotubes (MWNTs). Aside from establishment of the characteristic parameters of adsorption breakthrough, the performances of as-prepared MWNTs and commercial one are discussed. The chemical vapor deposition method was used to synthesize two kinds of MWNTs, where CNT 1 used acetylene as the carbon source and Fe(CO)5 as the catalyst; CNT 2 employed benzene as the carbon source and ferrocene as the catalyst. Both MWNTs were carried out the following experiments after purification. In addition, one commercial MWNTs, denoted as CBT, was selected for comparison. Before conducting the adsorption experiments, CNTs were probed by several material analyses. Toluene was chosen as the adsorbate, and its exit concentrations were measured by a direct-reading instrument. The adsorption temperature and relative humidity were the varying parameters in this study. Finally, the modified Wheeler equation was used to obtain the adsorption kinetic coefficient (kv), the adsorption amount (We), and the exponent of the time (n) by curve fitting. Meanwhile, the roles of adsorption temperature and relative humidity were discussed. The results show that P-CNT 1 has the smallest diameter obtained by TEM/HRTEM images, while it has the largest mean pore size by N2 adsorption/desorption isotherms. The XPS profiles indicate that the percents of O1s on CNTs surface increase after purification, but the changes of the percents do not obey a certain trend. Toluene adsorption on P-CNT 1 is affected the most significantly by adsorption temperature; on the other hand, the toluene adsorption on P-CNT 2 is the most dependent on the relative humidity. To sum up, the effects of adsorption temperature are more significant than that of relative humidity.