(686g) Zwitterion-Substituted Polysulfones As Fouling-Resistant Desalination Membranes

Authors: 
Green, M. D., Arizona State University
Yang, Y., Arizona State University
We have demonstrate a novel synthesis method to prepare a zwitterion-modified copolymer: poly(arylene ether sulfone-co-sulfobetaine arylene ether sulfone) (PAES-co-SBAES), which was blended with unmodified polysulfone (PSf) to prepare asymmetric, free standing membranes. The polymer's chemical structure was analyzed by 1H-NMR spectroscopy and the molecular weight of polymer was determined using size exclusion chromatography. Then, asymmetric PSf/PAES-co-SBAES blend membranes with various zwitterionic SBAES segment contents were fabricated via the non-solvent induced phase separation process. The cross-section morphology, surface hydrophilicity, and surface roughness of the membranes were analyzed by scanning electron microscopy, water contact angle measurements, and atomic force microscopy. The results indicated that both the porosity of the support layer and surface hydrophilicity increased drastically due to the incorporation of hydrophilic zwitterionic (or SBAES) segments. Surface roughness remained low for all membranes. The water permeance and antifouling ability of the PSf/PAES-co-SBAES blend membranes were both remarkably improved, with permeance values significantly higher than the native PSf and at or above levels of commercial polyamide membranes. Also, salt rejection was maintained at a high level, despite increases in hydrophilicity. The flux recovery when challenged with protein-rich solutions was ~93%, and complementary fluorescence microscopy experiments revealing very small levels of protein adhesion. Finally, no decrease in performance was observed when the membranes were challenged with chlorinated solutions. In summary, the strategy outlined to prepare zwitterion-modified polysulfones yielded asymmetric membranes with a high water permeance and salt rejection that also exhibit fouling resistance and tolerance toward chlorinated solutions. This will talk will discuss these developments and ongoing experiments to further improve the performance and scalability.