NAMS 2002 Workshop - ICOM 2008

the polymer dope was PEI (12 wt%), GBL (10 wt%) and nSMM (1.5 wt%) with a
balance of DMAc. The resulted mixtures were stirred in an orbital shaker at room
temperature for at least 48 h. The polymer dope was cast on a smooth glass
plate to a thickness of 0.30 mm using a casting rod at room temperature.
Subsequently, the cast film together with the glass plates was immersed for 1 h
in distilled water kept at room temperature. The membrane peeled off from the
glass plate spontaneously during gelation. All the membranes were then dried at
ambient conditions for 3 days.
The membranes were characterized using gas permeation test, measurement of
the liquid entry pressure of water (LEPw), scanning electronic microscopy (SEM),
and contact angle measurement. The effects of the SMM type on the membrane
morphology were identified, which enabled us to link the membrane morphology
to the membrane performance.
The membranes were further tested by DCMD for desalination of 0.5 M NaCl
solution and the results were compared to commercial polytetraflouroethylene
(PTFE) membranes (FGLP 1425, Millipore). nSMM2/PEI membrane yielded the
best performance among the tested membranes. In particular, it should be
emphasized that the above membrane was superior to the commercial one,
which was attributed to the fact that nSMM2/PEI had the highest pore
size/porosity ratio and the lowest LEPw among the laboratory made membranes.
It is worth mentioning that all the prepared membranes were tested successfully
for the desalination application. In other words, no NaCl was detected in the
permeate.
The SEM images showed that the laboratory made membranes had similar
finger-like structures regardless of the type of the nSMM used. The nSMM2/PEI
membrane exhibited macro-voids in the bottom layer, which might have
contributed to its DCMD flux that was the highest among all the tested
membranes.
A better and instructive understanding of hydrophobic/hydrophilic membrane
performance in MD has been obtained by finding the relationship between
membrane morphology and membrane performance. This will open a wide
avenue to the rational development of novel membranes for membrane
distillation.
References
1. M. Khayet, J.I. Mengual, T. Matsuura, J. Membr. Sci., 252 (2005), 101-113.
2. M. Khayet, T. Matsuura, M.R. Qtaishat, J.I. Mengual, Desalination, 199 (2006), 180-181.
3. D.E. Suk, T. Matsuura, H.B. Park, Y.M. Lee, J. Membr. Sci., 277 (2006), 177-185.