PVDF membranes formation, modification and application in pervaporation separation process

• Main Authors: Horng-Yuh Shiau, 蕭鴻裕
• Other Authors: Liao-Ping Cheng
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/38612748681727708885

碩士 === 淡江大學 === 化學工程學系 === 87 === Poly(acrylic acid) (PAA) was plasma-grafted unto porous PVDF membranes to form composite membranes, which were employed in pervaporation operations to separate water-ethanol solutions. It was found that the amount of grafted PAA affected the separation performance in the following manner: with increasing grafted PAA, the selectivity increased, permeability decreased, and the pervaporation separation index (PSI) increased first and then decreased. This indicated that there was an optimal value for grafted PAA. When the optimal value was exceeded, the selectivity was found to increase poorly, but the permeability decreased substantially, resulting in an overall decrease of PSI. To improve the permeability, the grafted PAA was treated with NaOH aqueous solutions to yield ionized membranes. While having much higher permeation fluxes, the selectivities of these membranes were largely maintained, and the PSI was found to increase 3-4 times. In addition to the amount of grafted PAA, the porous structure of the PVDF substrate also affected the pervaporation performance. Two types of substrates were studied in this research: the asymmetric and uniform PVDF membranes. In order to coat the substrate surface entirely with PAA, the uniform membrane required a larger amount of grafting. In general, the overall performance of the PAA/uniform membrane is better than that of the PAA/asymmetric membrane, with PSI of the former ca. 3 times higher than the latter.