Direct generation of an ultrathin (8.5 nm) polyamide film with ultrahigh water permeance via in-situ interfacial polymerization on commercial substrate membrane

Generation of ultrathin polyamide (PA) film has been recognized as an effective strategy for fabricating thin film composite (TFC) NF membranes with ultrahigh water permeance and desirable selectivity. However, direct synthesis of an ultrathin PA film via conventional in-situ interface polymerization (ISIP) on commercial substrate membranes has been widely considered impossible. Here we demonstrated this challenge can be surmounted by simultaneously optimizing the monomer concentration and substrate membrane selection. A defect-free PA film with thickness of 8.5 nm was directly formed on a commercial substrate membrane with smooth and hydrophilic surface, as well as medium pore size, only by using a high trimesoyl chloride (TMC) concentration of 0.1 w/v% and a low piperazine (PIP) concentration of 0.05 w/v %. The optimized TFC NF membrane prepared via this facile strategy exhibited an ultrahigh pure water permeance of 46.6 L m-2 h-1 bar- 1 and a desirable Na2SO4 rejection of 98.1%. As far as we know, this performance can exceed all the reported TFC NF membranes fabricated with conventional ISIP technique, and also be comparable to most state-of-the-art TFC NF membranes prepared with other complicated ex-situ interfacial polymerization (ESIP). The novel insight and feasible avenues of this study are expected to pave the way for the practical production and application of TFC NF membranes with ultrahigh water permeance.

Automated summary

The study demonstrated the successful synthesis of a defect-free PA film with a thickness of 8.5 nm on a commercial substrate membrane by optimizing monomer concentration and substrate membrane selection, resulting in a high pure water permeance and desirable Na2SO4 rejection for the prepared TFC NF membrane. This approach surpasses conventional ISIP technique and compares favorably with state-of-the-art TFC NF membranes prepared with other complex methods.