Tuning properties of silicalite-1 for enhanced ethanol/water pervaporation separation in its PDMS hybrid membrane

• Modified silicalite-1 compatibility with PDMS by tuning its sizes and morphologies.
• Improved silicalite-1 compatibility with PDMS through its functional modifications.
• Optimized ethanol/water separation performance of PDMS hybrid membranes.

The silicalite-1/PDMS hybrid membranes have been widely studied in alcohol perm-selective pervaporation separations. However, the poor compatibility between silicalite-1 particles and PDMS has already rebated the separation performance of these hybrid membranes. In this paper, two approaches were investigated to improve/tune the compatibility of the silicalite-1 particles and PDMS matrix. Firstly, silicalite-1 crystal particles with different sizes were synthesized. The effects of the particle size on the compatibility between silicalite-1 and PDMS were investigated. It was found that smaller silicalite-1 crystals (about 100 nm) have a better compatibility with PDMS matrix, thereby an enhanced separation performance of their hybrid membranes. Subsequently, the surface of silicalite-1 particles were modified through three kinds of silane coupling agents with different functional groups, which was confirmed to be feasible in increasing the compatibility with PDMS. In ethanol/water pervaporation separation, a higher selectivity was achieved in the PDMS hybrid membrane with TMDS-modified small silicalite-1 crystals. Moreover, silicalite-1 crystals provide many separate channels, so that the separation performance of the hybrid membrane has dramatically increased.

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