Development of a nanofiltration membrane for humic acid removal through the formation of polyelectrolyte multilayers that contain nanoparticles

Poly(sodium-4-styrenesulphonate) (PSS) and poly(diallyldimethylammonium chloride) have been employed to construct polyelectrolyte multilayers on a polyethersulphone substrate for use in the nanofiltration of humic acid. Self-synthesised Ag2O and commercial ZnO nanoparticles were incorporated into the multilayers separately, showing increases in the permeability from 7.53 +/- 1.83 to 8.39 +/- 1.37 and 8.62 +/- 1.03 L m(-2) h(-1) bar(-1), respectively, with no significant leaching observed in the permeates. All polyelectrolyte-modified membranes exhibited good film-formation stabilities and high humic acid retention capabilities, which ranged from 93.14 +/- 2.43 to 95.57 +/- 3.87%. Less humic acid solutes were deposited onto the surface of the polyelectrolyte-modified membrane, which was confirmed through field emission scanning electron microscopy images. The contact angle was reduced from 44.00 +/- 3.46 degrees to 39.10 +/- 3.47 degrees when the membrane surface was hydrophilised with PSS as the terminating layer.