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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