Study on fine-structure of polyamide thin-film composite membrane by positron annihilation spectroscopy and molecular simulation

• Main Authors: Yun-Hsuan Huang, 黃韻璇
• Other Authors: Juin-Yih Lai
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/32061608578470216550

碩士 === 中原大學 === 化學工程研究所 === 98 === To improve the permeation rate of polyamide (PA) membrane, a series of polyamide thin-film composite (TFC) membranes was prepared via interfacial polymerization of various water-soluble amine monomers (HA, DAPE and DAPL) and various acyl chloride monomers (SCC and tNBDC) on the surface of asymmetric modified polyacrylonitrile (mPAN) membranes. The PA/mPAN composite membranes were applied to the pervaporation separation of aqueous alcohol solutions. Attenuated total reflection infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to characterize the chemical structures and morphologies of the polyamide active layers of the composite membranes. The water contact angle measurement and the atomic force microscopy (AFM) were used to characterize the surface hydrophilicity and surface roughness of the composite membranes. The effect of the chemical structure of the monomers and the interfacial polymerization conditions, such as the monomer concentration of aqueous and organic solutions, the immersion time of aqueous solution, the polymerization time on the pervaporation performance were investigated. In addition, the influences of the membrane swelling on the changes of membrane fine-structure and pervaporation performance were systematically analyzed by positron annihilation spectroscopy (PAS) and molecular dynamics (MD) simulation. From the result of PAS analysis, the swollen polyamide active layer showed a large o-Ps lifetime than the dry active layer, and the PAS analysis at wet state was consistent with the pervaporation performance of the polyamide TFC membranes. The theoretical analysis by the MD simulation technique was showed that the side chain fluctuation of tNBDC would be improved more obviously than that in the SCC membrane after swollen, which led to from the more effective free volume in the wet tNBDC membrane. It was found that the DAPL-SCC/mPAN thin-film composite membranes prepared by immersing mPAN into 0.1 wt% aqueous DAPL solution for 60 sec and then contacting it with 0.5 wt% SCC in toluene organic solution for 15 sec showed the best pervaporation performance of 90 wt% ethanol aqueous solution at 25oC, the permeation rate was about 590 g/m2h and the water concentration in permeate was about 96.7 wt%.