New concept of thin-film composite nanofiltration membrane fabrication using a mist-based interfacial polymerization technique

Abstract

The conventional interfacial polymerization (CIP) technique used for preparing thin-film composite (TFC) nanofiltration membranes typically requires a large amount of monomers during polyamide (PA) synthesis where most of the monomers are discarded after cross-linking. Thus, a new fabrication concept is proposed in this work to synthesize a PA layer via a mist-based interfacial polymerization (MIP) technique where only a small amount of aqueous solution is dispersed as mist. This approach also eliminates the rubber-rolling step in CIP. In addition to forming a thinner and looser PA structure, the piperazine solution required in the IP reaction is significantly reduced, that is, 17 times lower than that of CIP. The microdroplet dispersion approach in MIP could form a higher cross-linked PA due to the high polymerization interface besides forming a higher free-volume selective layer due to the disruption in the PA repeat structure. Our findings revealed that the newly developed mist-based TFC membrane could achieve 9.08 L/m2·h·bar pure water permeability and 97.2% Na2SO4 rejection coupled with a complete flux recovery rate. As a comparison, the conventional TFC membrane only attained 2.84 L/m2·h·bar and 95.7%, respectively. The MIP technique could also be potentially considered for developing a nanofiller-incorporated TFC membrane due to the absence of the rubber-rolling step.