Structure Design And Properties Of Reinforced Polyacrylonitrile Hollow Fiber Membrane

The filaments were braided into a braid hollow tube as reinforcement via two-dimensional weaving techniques. Homogeneous reinforced (HR) polyacrylonitrile (PAN) hollow fiber membranes including PAN polymer solutions (coating layer) and the PAN braided tube reinforcement were prepared through the phase inversion spinning process. The performance of HR membranes varies with the polymer and additive concentration in the polymer solutions, and various spinning processes were studied. Heterogeneous reinforced PAN/PET (braid) and co-solvent heterogeneous reinforced PVDF/PAN (braid) hollow fiber membranes were prepared by the braided tube reinforced method, respectively. The interfacial bonding properties between the surface separation layer and braided tube were characterized by a variety of analytical test methods. The performance of reinforced PAN and cellulose acetate (CA) blended hollow fiber membrane were studied. The functional layer was modified through blending graphene oxide (GO) as an additive, which possessed lots of oxygen-containing groups. The application feasibility and membrane anti-fouling performance of the HR PAN and PAN/GO hollow fiber membranes were investigated through the membrane bioreactor (MBR) operation system.The HR PAN hollow fiber membranes were prepared based on the good thermodynamic properties and having co-solvent of the same material. The performance of HR membranes varies with the polymer and PVP concentration in the polymer solutions and various spinning processes were studied. The results showed that the co-solvent of polymer casting solution could lead to the braided tube surface swelling or dissolution, which made for a good interfacial bonding properties. The breaking strength of HR PAN hollow fiber membrane was up to 75 MPa or more, and the braided tube was the main provider of the mechanical properties. When the polymer concentration of 10-12wt.%, PVP content of 8 wt.%, the HR PAN hollow fiber membrane showed the optimal structure and performance.The PET braided tube heterogeneous reinforced PAN hollow fiber membranes and PAN braided tube co-solvent heterogeneous reinforced PVDF hollow fiber membranes were prepared, respectively. The results indicated that the key factor of interfacial bonding properties was the material thermodynamic compatibility between the surface separation layer and reinforcement. Compared to the three kinds of reinforced membrane, the interfacial bonding of the HR PAN was the optimal, followed by the co-solvent heterogeneous, the heterogeneous was the worst. The co-solvent could improve the interfacial bonding properties of reinforced hollow fiber membranes.The functional layer was modified through the blending method with CA. The results showed that there were a large number of interface microvoid pores on the reinforced PAN/CA blended hollow fiber membrane. With increase CA content the PAN changed from continuous phase to dispersed phase, at the same time, the CA transformed dispersed phase into continuous phase gradually. When the PAN was the continuous phase, the interfacial bonding of membrane was similar to homogeneous reinforced membrane. On the contrary, as the CA was the continuous phase, the interfacial bonding was likely to heterogeneous reinforced membrane.GO nanosheets were prepared by the modified Hummers’ method. Then homogeneous reinforced PAN/GO hollow fiber membranes were prepared, which the separation surface layer were modified by doping GO. The results indicated that the GO distributed in the surface and pore wall of the membrane. With increase GO content, the pore size distribution was narrower and the surface roughness increased. The introduction of GO endowed the PAN/GO membrane with improved not only hydrophilicity, but also permeability and antifouling properties.The anti-fouling performances of the HR PAN and PAN/GO membranes were investigated through the MBR operation system to deal with urban sewage. Membrane separation could strengthen the system effluent water quality and improve the stability, and the COD removal efficiency was more than 97%. The membrane fouling mechanism of the HR PAN and PAN/GO membranes was similar. Compared with the HR PAN membranes, the HR PAN/GO membranes had stronger antifouling properties, membrane fouling at a slower rate, lower cleaning frequency and a longer operating cycle in MBR system.