Interfacial polymerization using biobased solvents and their application as desalination and organic solvent nanofiltration membranes

Thin-film composite membranes are widely regarded as more sustainable technologies for desalination and organic solvent nanofiltration. However, the process of fabricating these membranes is not. This is because n-hexane, a toxic and hazardous solvent, or other fossil-derived oily solvents are used as the organic phase to fabricate polyamide selective layers of such membranes. Here we replaced fossil-derived solvents with benign, bio-renewable solvents that possess better environmental, health and safety metrics – cyclopentyl methyl ether (CPME) and 2-methyltetrahydrofuran (2-MeTHF). A fully aromatic polyamide thin film composite (TFC) membrane fabricated via CPME demonstrated a higher NaCl rejection (97.8%), while the same membrane fabricated using n-hexane only presented 92.4% rejection. Meanwhile a semi-aromatic polyamide TFC membrane fabricated with 2-MeTHF showed an ethanol permeance of 9.87 L m⁻² h⁻¹ bar⁻¹ and 97.1% RB rejection, 3.7-fold higher than the TFC fabricated using n-hexane. This demonstrated the feasibility and advantages of replacing toxic and hazardous solvents that have long been the standard solvents used in membrane fabrication, with benign alternatives. This work could potentially improve the sustainability of membrane fabrication.