Forward Osmosis Membrane Surface Modification By In Situ Peg-Ylation for Enhanced Organic Fouling Resistance

Forward osmosis (FO) is an emerging technology that holds significant promise in a host of applications, including wastewater reclamation and treatment, and seawater desalination. Nevertheless, membrane fouling remains a technical obstacle affecting this technology, decreasing permeation fluxes and membrane life. This work presents the fabrication of a thin-film composite (TFC) FO membrane with enhanced membrane fouling resistance. To this end,we modified the membrane in situ, grafting Jeffamine (a block copolymer of poly(ethylene glycol) and poly(propylene glycol)) to dangling acyl chloride surface groups on the nascent polyamide active layer. Active layer surface characterization by fourier transform infrared spectroscopy with attenuated total reflectance (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle and zeta potential measurements, confirms the presence of Jeffamine on the membrane surface and its increased hydrophilicity compared to pristine(unmodified) polyamide membranes. We demonstrate the improved fouling resistance of our modified membranes through accelerated dynamic fouling experiments in FO mode using a simulated wastewater feed solution at high alginate loadings. Enhanced antifouling properties are observed for the in situ modified membranes, as evidenced by the lower flux decline observed compared to pristine polyamide (14.3±2.7 % vs. 5.8±5.8%, respectively). AFM adhesion force measurements between the modified membrane and a carboxylate-modified latex particle, an appropriate surrogate for the alginate foulant, show weaker membrane-particle interactions for the modified membranes compared to the control, further confirming the enhanced fouling resistance of the in situ modified membranes.