Preparation of silicalite-polyamide composite membranes for desalination

Silicalitepolyamide composite membranes were synthesized via interfacial polymerization on a commercial polysulfone substrate, for the purpose of studying the effect of the addition of silicalite nanocrystals on the desalination property of polyamide membrane. The scanning electron microscopy (SEM) images showed that both plain polyamide membrane and silicalitepolyamide composite membranes exhibited rough surface morphology which is similar to the commercial polyamide membranes. The existence of silicalite nanocrystals in the silicalitepolyamide composite membrane was confirmed by energy dispersive X-ray spectroscopy (EDXS) and high-resolution transmission electron microscopy (HRTEM). The effect of loading of silicalite nanocrystals on the desalination property of membranes was examined. By increasing the loading of silicalite nanocrystals, the water flux of silicalitepolyamide composite membranes increased, whereas the salt selectivity decreased significantly. Plain polyamide membrane had salt rejection of 98.1% and a flux of 5.07 x 10(-7) m3/m2 center dot s, whereas the silicalitepolyamide composite membrane, prepared from trimesoyl chloride (TMC)hexane with 0.5% (w/v) silicalite, had a water flux of 2.74 x 10(-6) m3/m2 center dot s and NaCl rejection of 50% at a feed pressure of 34.48 bar by using 2000 ppm salt solution as the feed. The transport mechanisms of the silicalitepolyamide composite membranes were discussed. (C) 2011 Curtin University of Technology and John Wiley & Sons, Ltd.