Performance enhancement of nanofiltration membranes via surface modification with a novel acylation reagent

Acyl chloride monomers have been serving as the dominant acylation reagent for preparing thin-film composite (TFC) nanofiltration (NF) membranes over the past few decades. Herein, a novel acylation reagent (trimellitic anhydride, TMA) was exploited in conjunction with trimesoyl chloride (TMC) to undergo interfacial polymerization with piperazine (PIP) on the polysulfone substrate membranes. The introduction of TMA enabled the deeper diffusion of PIP monomers into the organic phase, resulting in the creation of novel circular-shaped protuberances on the top surface of the polyamide layer and the significant increase in the effective membrane area. Besides, abundant in-situ carboxylic groups were generated in the polyamide layer, conducive to both the surface hydrophilicity and negative charge density. Consequently, with an addition of 0.03 wt% TMA, pure water flux reached up to 15.3 L m −2 hour −1 bar −1 , almost 2.2 times that of the pristine membrane, and high rejection of Na 2 SO 4 (97.3%) was maintained, evincing the superior desalination performance of the TMA-modified membranes. The interaction mechanism between TMA, TMC, and PIP was described in detail. Furthermore, the TMA-modified membranes exhibited a stable separation performance over the long-running process.