Surface Modification of Nano-porous Membranes and Their Use in Electroosmotic Flow

• Main Authors: Yi-Hsin Hu, 胡譯心
• Other Authors: Shih-Ming Lai
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/49763965950962537064

碩士 === 雲林科技大學 === 化學工程與材料工程研究所 === 96 === In this study, electroosmotic (EO) pumps were built using anodic aluminum oxide membrane (AAOM) as the substrate, on which silane couple agents (SCAs) were functionalized the membrane surface in order to achieve higher EO flow rate and efficiency. The four membranes used for the test of EO pump’s performance include: bare AAOM, H2O2 modifeid AAOM, (3-Aminopropry)trimethoxysilane (APS)-coated AAOM and (3-Mercaptopropyl)trimethoxysilane (MPTS)-coated AAOM (with H2O2 oxidization). The results show that the order of normalized flow rate (zeta potential) was: APS-coated AAOM > MPTS-coated AAOM (with H2O2 oxidization) > H2O2-modified AAOM > bare AAOM. And, and the order of efficiency of EO pump was: MPTS-coated AAOM (with H2O2 oxidization) > H2O2-modified AAOM > APS-coated AAOM > bare AAOM. It is noted that the efficiency of EO pump was influenced not only by the flow rate but also by the back pressure and the current. Therefore, although the APS-coated membrane had the highest surface zeta potential (the highest EO flow rate), its efficiency, being just larger than that of the bare AAOM, was smaller than those of the MPTS-coated AAOM (with H2O2 oxidization) and the H2O2-modified AAOM. It is demonstrated that coating of high charged functional groups on the membrane surface can promote a high zeta potential and then enhance the flow rate and efficiency of EO pump. In addition, using the positive charged bare AAOM and operated under constant ionic concentration and pH in electrolyte, the effect of the type of anion in electrolyte (CH3COO－, CO32－, PO43－) on the EO flow rate was investigated. The results show that, when the ionic concentration was kept low enough to neglect the screening effect occurred on the membrane surface, the higher the charge and the lower the mass, i.e. the lower the mass to charge ratio, of the anion, the larger the EO flow rate was. It is suggested that, in order to achieve a higher EO flow rate, the electrolyte with an anion of low mass to charge ratio should be adopted.