Surface Modification of Nanofiltration Membranes by Interpenetrating Polymer Networks and Their Evaluation in Water Desalination

Membrane separation is the most widely used technology in desalination to produce drinking water that requires improved permeability and salt rejection. The objective of the present study is to modify fully aromatic polyamide (NF90) and semiaromatic poly(piperazine-amide) (NF270) nanofiltration membranes via interpenetrating polymer networks of [3-(acryloylamino)propyl]trimethylammonium chloride (ClAPTA), 2-acrylamide-2-methyl-1-propanesulfonic acid (APSA), and glycidyl methacrylate– N -methyl- d -glucamine (GMA-NMG). The surface topography of the modified NF270 and NF90 membranes was analyzed by SEM and AFM. The modified NF270 membrane showed more significant roughness changes than the original (39%), while the modified NF90 membrane showed slight changes (7%). The FTIR results showed the chemical modifications introduced in the membranes. The best modified NF90 membrane (0.13 M GMA-NMG-0.07 M APSA) showed an 84.3% and 0.6% increase in water flux and chloride rejection for filtration of a model solution, respectively, compared to the commercial membrane. Furthermore, the best membrane modification was achieved with P(ClAPTA- co -GMA-NMG), increasing seawater permeability by 300% without modifying the high rejections of the original membranes. This work provides a guide to improving the permeability of NF membranes without sacrificing a higher species rejection by modification with interpenetrating polymers.