Preparation And Antifouling Property Of Polyacrylonitrile (PAN)-Sulfobetaine Copolymer Ultrafiltration Membrane

Polyacrylonitrile (PAN) is one of the most popular ultrafiltration membrane materials due to its excellent chemical resistance, thermal, and mechanical stability. However, the inherent poor hydrophilicity seriously limits its separation efficiency. In this paper, with the aim of reducing the membrane fouling during bioseparation, copolymerizing modification of the PAN ultrafiltration membrane and the preparation of modified membranes were both investigated.A novel membrane material PAN-based zwitterionic copolymer was synthesized. PAN-based zwitterionic membrane and its blend membranes were prepared by a phase inversion method through a wet process. Water contact angles were measured to evaluate the hydrophilicity of membrane surface, X-ray photoelectron spectroscopy (XPS) analysis was used to characterize the surface composition, and scanning electron microscopy (SEM) was used to observe the morphology of the PAN-based zwitterionic blend membranes. The hydrophilicity and the antifouling (especially irreversible fouling) property of the PAN-based zwitterionic blend membranes were efficiently improved with an increase of the sulfobetaine groups on the membrane surface. The control PAN membrane had a flux recovery ratio of 47%, while the PAN-based zwitterionic membrane had a flux recovery ratio of 95%. The flux recovery ratio of the PAN-based zwitterionic membrane was retained at 92% after three cycles of BSA solution ultrafiltrationZwitterionic copolymer PAN-DMMSA composed of acrylonitrile (AN) and N, N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) (DMMSA) was synthesized. PAN-DMMSA membrane was then fabricated through phase inversion method in a wet process. The distinct stimuli-response behaviors of PAN-DMMSA membrane were observed as indicated by the fact that the flux of the membrane increased with the increase of pH value and ionic strength. Fourier transform infrared spectroscopy (FT-IR) was introduced to investigate the responsive chemical changes of the membranes under different pH values and ionic strengths. FT-IR analysis confirmed that the dipole-dipole interaction of R4N+ and SO3- groups in PAN-DMMSA membrane was substantially disrupted under the exerted stimuli. The stimuli-responsive behavior was tentatively elucidated based on the specific dipole-dipole interaction of oppositely oriented groups.Different concentration of the PAN-DMMSA copolymer in casting solution was chosen to modulate the rejection ratio of BSA molecule.The efficient separation of the simulated fermentation solution comprised with BSA and yeast was realized with PAN-DMMSA membrane. In the ultrafiltration process, BSA could penetrate the PAN-DMMSA completely and did not cause substantial membrane fouling, while rejection ratio of yeast was 100%. When separating the simulated fermentation solution, fluxes of the PAN-DMMSA membranes were slightly less than the flux for pure BSA solution. But the fluxes were still above 60 L/(m2h) and the flux recovery ratios of the membranes were all beyond 80%.