Tuvia Turkeltaub

Seawater requires pretreatment before reverse osmosis (SWRO) to minimize membrane fouling, but conventional methods increase energy use and chemical consumption, and their robustness when feedwater quality fluctuates is low. Ultrafiltration (UF) offers a promising alternative, producing higher-quality permeate, tolerating feedwater variability, and lowering chemical use; however, UF membranes still suffer from fouling during seawater treatment. Polyzwitterionic (PZI) brushes grafted onto porous membranes show excellent antifouling in water treatment, but their application in seawater pretreatment remains unexplored. Here, poly(sulfobetaine methacrylate) (polySBMA) brushes were grafted onto polyethersulfone UF membranes via atom transfer radical polymerization and evaluated using real seawater (RSW) supplemented with dissolved organic carbon derived from seawater algae. Surface analysis confirmed successful grafting, with brush thickness increasing with polymerization time (1–12 h). Quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy showed that brush swelling increased in Milli-Q water and more in seawater. Fouling tests with the DOC-enriched RSW demonstrated improved antifouling relative to unmodified membranes, dependent on brush thickness. Membranes grafted for 6 h operated stably for 8 days at 95% water recovery, with only a 1.42-fold transmembrane pressure increase, whereas unmodified UF membranes doubled TMP within 24 h. QCM-D and post-fouling membrane analyses confirmed the antifouling effects of the polySBMA brushes. Seawater quality after pretreatment met standards for RO feedwater. RO desalination of pretreated seawater remained stable over 12 h, demonstrating that the grafted membranes of the present study are also effective in reducing fouling, thereby enhancing the overall robustness of the SWRO process.