One-step fabrication of PVDF/BTMSPA composite membranes for enhanced n-butanol/water separation

A novel polyvinylidene fluoride/bis(trimethoxysilylpropyl)amine (PVDF/BTMSPA) asymmetric composite membrane was fabricated through a one-step vapor-induced phase separation (VIPS) process. The hydrophilic BTMSPA monomers preferentially migrated to the membrane surface during VIPS, where they underwent hydrolysis and condensation to form a dense skin layer, while the hydrophobic PVDF matrix solidified into a porous support layer. By varying the VIPS duration, the skin layer structure could be tuned from porous to dense. At a VIPS time of 0.5 h, a spontaneously formed dense-skinned PVDF/BTMSPA composite membrane was achieved. The membrane demonstrated preferential adsorption of n-butanol over water, exhibiting optimal separation performance for a 4 wt% n-butanol/water mixture at 70 °C, with a flux of 1980 g/m 2 ·h and a separation factor of 63.65. This work not only provides a facile and efficient VIPS-based strategy for fabricating asymmetric composite membranes but also highlights the potential of PVDF/BTMSPA membranes for n-butanol/water separation applications.