Fabrication of Low-Fouling Ultrafiltration Membranes Using a Hydrophilic, Self-Doping Polyaniline Additive

A simple, scalable method for fabricating fouling-resistant ultrafiltration membranes is described. A self-doped, sulfonated form of polyaniline was blended into polysulfone (PSf) ultrafiltration (UF) membranes to enhance hydrophilicity and fouling resistance. Polyaniline in its base form was sulfonated with fuming sulfuric acid, yielding sulfonated polyaniline (SPANi) with a degree of sulfonation of ∼0.5 confirmed by XPS. The SPANi polymer was dedoped and dissolved in a solution of polysulfone in N-methylpyrollidone at varying concentrations. During phase inversion to form membranes, SPANi is redoped and precipitated within the PSf membrane films in a facile one-step process. Composite membranes containing increasing amounts of SPANi were compared to the pure PSf membranes to determine changes in performance, hydrophilicity, and antifouling characteristics. The composite membranes exhibit fluxes similar to those of the pure PSf membrane and maintain rejection properties similar to those of current UF membranes. Captive bubble contact angle measurements and atomic force microscopy suggest increasing membrane hydrophilicity with increasing SPANi content. During flux decline and recovery experiments, SPANi/PSf composite membranes exhibited higher flux recovery than a pure PSf membrane, with the best performing membrane regaining 95% of its original flux after being washed with deionized water, demonstrating a high resistance to irreversible fouling.