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 degrees 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.

Automated summary

Surface modification via heat curing and grafting monoethanolamine (MEA) can enhance the pure water permeability and Na2SO4 rejection of polyamide nanofiltration membranes. The optimized membrane modified with 0.5 wt% MEA showed high Na2SO4 rejection and negative NaCl rejection when treating a mixed salt solution. This study provides insights for developing high permselectivity NF membranes through surface modification.