Breaking through permeability-selectivity trade-off of thin-film
composite membranes assisted with crown ethers
Abstract
In this study, we deployed a modified interfacial polymerization process
to incorporate multifunctional crown ethers (CEs) into thin-film
composite (TFC) polyamide membranes. These CE additives acted as both
the phase-transfer catalyst and co-solvent to facilitate the diffusion
of amine monomers into the organic phase and also enhanced the free
volume content of the selective layer, facilitating water transport and
inhibiting the diffusion of draw solutes. Various characterization
techniques were employed to elucidate the modification mechanism as a
function of CE chemical and physical properties on the microstructure of
resultant TFC membranes and consequently separation performances.
Compared to TFC membranes produced from traditional interfacial
polymerization method, CE-modified membranes exhibited a 146% water
flux enhancement and 59% lower reverse salt fluxes with a suitable draw
solution. CE-modified membranes also exhibited improved antifouling
performance with a lower flux drop (34% decline) and a higher flux
recovery ratio (38% improvement).