The research of the adsorption properties between multi-walled carbon nanotubes and bisphenol A

• Main Authors: Yi-lin Yu, 余翊菱
• Other Authors: Ching-Ju Monica Chin
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/90170654416708813062

碩士 === 國立中央大學 === 環境工程研究所 === 99 === Due to various applications of carbon nanotubes, their discharge into natural water is expected and their adsorption phenomena should be studied to understand their fate and transport. In this study, four common chemical oxidation methods were chosen to modify multi-walled carbon nanotubes (MWCNTs), they are, HNO3, piranha, NH4OH 25 %: H2O2 30 % = 50:50, and KOH. Bispenol A (BPA) were adsorbed to investigate the influences of different oxidation methods of MWCNTs on the adsorption mechanisms. It was found that, with proper oxidation parameters, nitric acid could introduce significant amount of oxygen-containing surface groups without altering the surface structure. Oxidation by KOH increased the surface area of MWCNTs dramatically and introduced oxygen-containing surface groups of the amount similar to that nitric-acid-treated MWCNTs. Thus the adsorption of BPA was only conducted by A-MWCNTs (as-purchased MWCNTs), N-MWCNTs (oxidized by HNO3), and K-MWCNTs (oxidized by KOH). The adsorption rates the fastest to the slowest were A-MWCNTs, N-MWCNTs, and K-MWCNTs and could be described by the pseudo-second order kinetic model. The adsorption capacities of A-MWCNTs, N-MWCNTs, and K-MWCNTs were 0.3116, 0.2039, and 0.5919 mmole/g, respectively. Comparison between the adsorption capacities of A-MWCNTs and N-MWCNTs showed that the oxygen-containing group hindered the π-π interactions and reduced the adsorption of BPA. The adsorption capacity was affected by solution pH, mainly due to the dissociation of BPA. Deprotonation of BPA leaded to electrostatic repulsions between BPA molecules and the surface of MWCNTs at high solution pH and, thus, reduction in the adsorption capacity.The enthalpy and free energy showed that adsorption of BPA on MWCNTs were exothermic and spontaneous.