Coupling heat curing and surface modification for the fabrication of high permselectivity polyamide nanofiltration membranes

Surface modification is an efficient post-treatment method to optimize the properties of nanofiltration (NF) membranes. Here, we report a facile surface modification strategy coupling with heat curing for grafting monoethanolamine (MEA), a monomer containing both a primary amine and a primary alcohol group, onto a nascent polyamide NF membrane. With grafting 0.5 wt% MEA at 50 °C, the pure water permeability of the polyamide NF membranes was improved from 7.9 to 19.5 L m−2 h−1 bar−1 due to their enhanced physicochemical property, such as superior hydrophilicity, rough surface morphology, and enlarged membrane pores. Meanwhile, the rejection of Na2SO4 remained above 97.5%. More importantly, the optimal membrane modified with 0.5 wt% MEA exhibited a high Na2SO4 rejection of 99.1% and a negative NaCl rejection of −20.1% when treating a mixed salt solution containing 2 g/L Na2SO4 and 2 g/L NaCl. Our study provides a novel insight for the fabrication of high permselectivity NF membranes via surface modification. [Display omitted] •Surface grafting was creatively coupled with heat curing in water.•Monoethanolamine molecule was successfully grafted onto the nascent membrane, rendering a better hydrophilic nanofiltration membrane.•The modified membrane exhibited enhanced pure water permeability of 19.5 L m−2 h−1 bar−1.•The modified membrane owned superior Cl−/SO42− selectivity.