Compared with new methodologies for the fabrication of thin film composite (TFC) nanofiltration (NF) membrane, surface modification gives one of the most feasible and effective solution to improve the performance of multiple membranes. In order to repel multivalent ions, herein we photo-grafted electrostatically charged copolymers onto the surface of commercial nanofiltration membranes via phenylazide photochemistry. The membrane performance with copolymers containing a positively charged quaternary ammonium, a negatively charged sulfonate and a neutral zwitterion, respectively. In order to repel multivalent ions, herein we photo-grafted electrostatically charged copolymers onto the surface of commercial nanofiltration membranes. Analytical techniques such as, scanning electron microscopy (SEM), Atomic force microscopy (AFM) and elemental analysis are used to characterize the membrane morphologies. In addition, contact angle analysis and zeta potential are also taken to investigate the physiochemical, surface charge and electrochemical properties of the membrane surfaces. Compared to pristine NF90 polyamide membranes, the zwitterionic modified membrane possesses lower surface roughness, improved hydrophilicity as well as an excellent CaCl2 and Na2SO4 rejection of 98% and 99% respectively due to a combination of both Donnan and size-exclusion effects. We attribute the order of rejection (SO42- &gt; Ca2+ &gt; Cl- &gt; Na+) to ionic size, which governs the hydrated radius. Overall, this study established an industrial applicable modification to NF membranes for high divalent cation rejection.

Electrostatically varied grafted copolymers for enhancing multivalent ion rejection for nanofiltration

2019 Fall National Meeting

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