Abstract :
Dehydration of ethanol is studied using various PVA-based membranes. Due to its high solubility in water, PVA membrane has a great
extent of swelling in ethanol–water mixture, resulting in a remarkable decline of selectivity. To restrict the extent of swelling, PVA
membranes were chemically modified by crosslinking reaction by glutaraldehyde. Crosslinking reaction was conducted by using two
concentrations of glutaraldehyde, i.e. 0.025 and 0.100% by weight, and the degree of crosslinking was varied by changing the reaction time.
The difference degree of crosslinking was examined by the extent of swelling. Those modified membranes were performed by pervaporation
to study the effect of crosslinking on separation process. Crosslinked PVA-membrane with 26.5% swelling degree, produced flux
0.28 kg/m2 h, and separation factor 104 at the condition of pervaporation at 40 8C and 0.4 mbar downstream pressure, using feed solution 90
wt% of ethanol. The present of charged groups in PVA-N and PVA-It membranes decrease the swelling degree to 15.65 and 14.00%,
respectively. At feed concentration of ethanol 96% by pervaporation, PVA membrane with swelling degree 26.5%, produced flux,
JZ0.279 kg/m2 h and separation factor, aZ107; PVA-N membrane flux, JZ0.123 kg/m2 h and separation factor, aZ216; PVA-It
membrane flux, JZ0.119 kg/m2 h and separation factor, aZ228. The present of charged groups increase selectivity, however it decrease
flux. By decreasing down stream pressure from 0.4 to 0.14 mbar at the same pervaporation condition, the membrane selectivity changed to a
higher values, PVA membrane flux, JZ0.189 kg/m2 h and separation factor, aZ335; PVA-N membranes flux, JZ0.089 kg/m2 h and
separation factor aZ709; PVA-It membranes flux, JZ0.086 kg/m2 h and separation factor aZ837.
The presence of charged groups in polymers and the down stream pressure influence potentially to improve membrane selectivity.
Substitution of anionic and cationic charged groups to PVA membrane, such as PVA-N and PVA-It, influenced to flux and separation factor.
PVA-It membrane processes the lowest flux, caused by the strong interaction between polymer chain due to the present of dicarboxyl groups,
however the hydrophilic anionic groups promoted high selectivity of PVA-It to water.
q 2004 Elsevier B.V. All rights reserved.
