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Different polydimethylsiloxane (PDMS) nanocomposite membranes were synthesized by incorporating various contents of nanosized silica particles to improve the PDMS pervaporation (PV) performance. A uniform dispersion of silica nanoparticles in the PDMS membranes was obtained. The nanocomposite membranes were characterized morphologically by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that surface roughness increases by incorporating silica, and this decreases absorption of penetrants on the membrane. Swelling studies showed that the presence of silica nanoparticles into the PDMS membranes decreases degree of swelling, which can be attributed to rigidification of the PDMS matrix. Additionally, the results revealed that helium permeability decreases through the nanocomposite membranes, due to the more polymer chains packing. Effects of silica on recovery of isopropanol (IPA) from water mixtures were also investigated. Based on the results, incorporating silica nanoparticles promotes significantly the PDMS membrane selectivity because the polymer chains are rigidified and also the polymer free volume decreases. However, permeation flux decreases as diffusion of the penetrants reduces in the presence of silica nanoparticles within the PDMS membranes. As PV performance depends on operating conditions, effects of feed composition, and temperature were also studied. Moreover, recoveries of IPA, ethanol, and methanol from water mixtures were compared using the PDMS-silica nanocomposite membranes. The results demonstrated that polarity and solubility of alcohols affect permeation flux and selectivity resulting in the higher permeation flux and selectivity for IPA.

9In this work, a novel chemical modification is introduced to fabricate poly (ether block 10 amide)/silica, (PEBA/SiO2), nanocomposite membranes for separation of CO 2 from syngas and 11 natural gas streams. Cis-9-octadecenoic acid (OA) was utilized for surface modification of the 12 nanoparticles to restrict their agglomeration within the polymeric matrix. To our best knowledge, 13 there is no evidence about application of this modifier agent for fabrication of nanocomposite 14 membranes. Separation performance of the fabricated membranes was investigated by pure and 15 mixed gas permeation experiments. Incorporation of the modified nanoparticles into the 16 polymeric matrix improved separation performance of the fabricated nanocomposite membranes.17 For instance, by increasing loading content of the SiO 2 nanoparticles from 0 wt. % (the neat 18 PEBA membrane) to 8 wt. %, at 25 °C and 2 bar, ideal selectivity values of CO 2 /H 2 , CO 2 /CH 4 19 and CO 2 /N 2 were improved from (9, 18 and 61) to (17, 45 and 137), respectively.20 21

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