Ethanol recovery from its dilute aqueous solution using Fe-ZSM-5 membranes: Effect of defect size and surface hydrophobicity

•The membrane is modified by DMS molecules to change its surface hydrophobicity.•The influence of defect size and surface hydrophobicity is investigated separately.•The result can be used to optimize zeolite membranes and the pervaporation process.

The seeded growth method was used to prepare Fe-ZSM-5 membranes on porous α-Al2O3 substrates. After template removal, the Fe-ZSM-5 membrane was chemically modified using dodecyltrimethoxysilane (DMS). The experimental results based on diffuse-reflectance FT-IR spectroscopy, electron probe microanalysis (EPMA), 29Si NMR spectroscopy and contact angle measurements revealed that DMS molecules reacted with silanols on the membrane surface. The hydrophobicity of the Fe-ZSM-5 membrane after surface modification was greatly enhanced. The pervaporation performance of the Fe-ZSM-5 membrane for dilute ethanol aqueous solution indicated the membrane defects played a fundamental role in the selective permeation of ethanol, and the surface hydrophobicity would become important for the membrane with meso-sized defects.

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