| Summary: | 碩士 === 淡江大學 === 化學工程學系 === 86 === PVDF membranes were synthesized either by wet-quenched or dry-wet
methods and employed in pervaporation processes to separate organic
aqueous solutions. It was found that these membranes could separate
effectively benzene from water and that the crystallinity of PVDF and the
membrane formation conditions (especially, solvent type, and standing time
in dry-wet method) affected the separation performance. For the case of feed
containing 1000 PPM benzene in water, the permeation flux were the largest
for the membrane prepared by solvent NMP; there was no separation of
benzene from water, however. The membrane prepared by TEP had a flux of
121 g/m2hr, which was intermediate of those prepared by NMP and DMF
. Moreover, for membranes prepared by dry-wet method, both the permeation
flux and the separation factor were found to be lower for shorter standing
times.
For pervaporation of ethanol-water solutions, all prepared membranes
could avoid the azeotropic condition. In particular, Kynar 740 membrane,
whose crystallinity was the highest, exhibited a different pervaporation
behavior. At low ethanol concentrations, the permeate contained more
ethanol than water; but the situation reversed (permeate was richer in water)
when the feed ethanol exceeded 60 wt. %. As a result, one can choose among
various types of PVDF membranes to fit into practical needs. In addition,
because the preparation procedures for forming these membranes are
relatively simple, reproduction of specific membrane structures is almost
guaranteed.
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