Title:
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The Dehydration of Aprotic Solvents by Pervaporation
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The application of pervaporation to the dehydration of aprotic solvents was investigated in this study.
The performance of a commercial membrane, Celfa CMC-VP-31, was evaluated for the dehydration
of tetrahydrofuran (THF) and dimethylformamide (DMF). The membrane was demonstrated to
successfully dehydrate THF and calculations of water and THF permeance performed. When the
membrane was applied to the dehydration of DMF, delamination of the top selective layer was
observed and thus the membrane was deemed unsuitable for DMF dehydration.
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Polyaniline (PAni) was identified as a suitable candidate polymer for the formation of an aprotic
solvent stable hydrophilic pervaporation membrane. PAni was synthesised in the lab and preparation
conditions optimised and scaled-up to produce polymer with consistent batch to batch properties, in
suitable quantities, to fabricate���· membrane sheets with sufficient surface area for testing. Casting
solutions comprising of 20 wt% PAni were stabilised using an amine, 4-methyl piperidine, to prevent
gelation and cross-linking prior to casting. Membranes were cast on a polyester non-woven backing
and phase inverted in water to produce an asymmetric membrane structure. Scanning Electron
Microscopy was used to examine the structure of the membranes formed. The effects of thermal
treatment on the membrane film and polymer were investigated by a number of analytical techniques
in order to devise a suitable procedure for membrane stabilisation.
Thermally cross-linked PAni membranes were demonstrated to be water selective and stable in THF,
DMF, ethyl acetate and ethanol. Permeance correlations with temperature were constructed to describe
the performance of the membrane discs tested during solvent dehydration and compared to
experimental data. Transport across the membrane was reported to be solubility dominated for all of
the solvent systems tested.
Finally, an examination of the reproducibility of membrane performance was made and further tests
performed, to better understand variations observed in membrane pervaporation performance.
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