Preparation and performance of thin film composite solvent nanofiltration membrane based on fluorinated diamine monomers

Abstract

The high perm-selectivity and long-term solvent resistance of organic solvent nanofiltration (OSN) membranes in various solvents pose significant challenges for their development. In this study, ultra-low content mixture of fluorinated diamine (5-trifluoromethyl-1,3-phenylenediamine or 4-trifluoromethyl-1,2-phenylenediamine) and m-phenylenediamine (MPD) as aqueous phase monomers and ultra-low content trimesoyl chloride (TMC) in n-hexane as organic phase monomer were used to perform interfacial polymerization (IP), then followed by crosslinking and solvent activation. By this way, two kinds of ultra-thin and ultra-smooth fluorinated polyamide OSN membranes were achieved. Under optimized conditions, these two kinds of OSN membranes, TFC-5F2,II and TFC-4F1,II, have surface roughness of 2.5 and 3.0 nm, respectively. They show ethanol permeance of 73.9 and 60.9 L m−2 h−1 MPa−1, and RDB rejection of 98.5% and 99.2%, respectively, using 100 mg L−1 rhodamine B / ethanol solution as feed. They show ethyl acetate permeance of 209.4 and 117.0 L m−2 h−1 MPa−1, respectively, and catalyst rejection of 98.2% and 98.8%, respectively, using 50 mg L−1 Jacobsen catalyst/ethyl acetate solution as feed. Meanwhile, they have pure n-hexane permeance of 32.5 and 36.8 L m−2 h−1 MPa−1, respectively. Moreover, they show excellent stability in highly polar solvents, thus have good application prospects in the separation and purification of various organic solvent systems.