| Membrane separation technology is an important high-tech to solve energy, resources, and environmental pollution problem of the time. It is a technology foundation of the sustainable development. The quality and category of domestic ultrafiltration (UF) membranes still need improving. Research in UF membrane technology has great significance of theoretical and practical values. The most concentrated research focused on UF membranes is to enhance anti-fouling property and to reduce costs. Poly (vinylidene fluoride) (PVDF) is a preferred material for membrane preparation. It has excellent chemical stability, thermal stability, strength, and toughness. However, these membranes are susceptible to be fouled by oils and proteins because of their high hydrophobicity, which limits their application in filtrating aqueous mixtures. Consequently, modification plays a very important role in PVDF membrane application. Nano-materials are recognized as one of the focus on the development of new materials. The combination of nano-inorganic materials and PVDF plays their respective advantages, makes up their deficiencies, exploits a comprehensive performance, and meets the specific needs.Nano-SiO2, nano-NaY zeolites, nano-CaCO3, and nano-ZnO modified PVDF UF membranes were prepared by phase inversion method in this study, respectively. Meanwhile, the effects of inorganic nano-particles on the morphology, thermal stability, mechanical property, hydrophilicity, membrane flux, and antifouling performance of the membranes were discussed as well.PVDF membranes with low contents of mesopours silica SBA-15 particles (≤0.72wt%, by weight of PVDF) were prepared by a phase inversion process. The thin membranes were then characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), tensile stress tests, thermogravimetric analysis (TGA), contact angle technique, water flux and bovine serum albumin (BSA) retention to investigate the influence on the final properties of the developed membrane. The resulting modified membrane exhibited no particular influence on the structures of the air surface, cross-section and inner pores. The experiment results confirmed that the addition of low contents of SBA-15 particles could effectively improve membrane hydrophilicity, antifouling performance, mechanical property and thermal stability, and increased membrane flux with the resistance of BSA solution above 87%.The comparison of the morphology and performance was carried out between virgin PVDF UF membrane and PVDF composite membranes with low content of two different SiO2 (N-SiO2 and M-SiO2 particles). Cross-sectional area and surface morphology of the membranes were observed using SEM and atomic force microscope (AFM). Surface hydrophilicity of the porous membranes was determined by the measurement of a contact angle. Performance tests were conducted on the composite membranes by water flux and BSA retention. Mean pore size and surface porosity were calculated based on the permeate flux. Thermal stability and mechanical stability were determined with TGA and tensile tests. The results indicated that the N-S1O2/PVDF (P-N) membranes possessed bigger average pore size and porosity, which led to higher water flux and a slight decline of BSA retention. And M-SiO2/PVDF (P-M) membranes had better mechanical stability and antifouling performance with enhanced membrane hydrophilicity and decreased membrane surface roughness. Both of the P-N and P-M membranes displayed typical asymmetric morphology and improved thermal stability.A novel antibacterial UF membrane obtained by blending PVDF with Ag+ exchanged NaY zeolite particles (AgNaY) was prepared using phase inversion methods. The AgNaY hybrid PVDF membranes exhibited excellent and long-lasting antibacterial activity against Escherichia coli (E. coli). Its antibacterial activity was improved with increased Ag+content. The hydrophilicity of P-AgNaY-3 was improved with a low contact angle of 81.6°. Compared with P-0, the permeate performance, thermal stability, and mechanical properties of P-AgNaY was improved with a steady BSA retention above 92%. Antibacterial activity of the membranes against E. coli was measured using the halo zone test. The characterization of AgNaY/PVDF hybrid membranes was investigated by scanning electron microscope, X-ray diffraction (XRD), tensile stress tests, TGA, contact angle tests, pure water flux, and permeation flux.PVDF membranes with different contents of nano-CaCO3 particles were prepared by a phase inversion process. The effect on morphology, mechanical property, thermal stability, hydrophilicity, and filtration performance of the modified membranes were discussed. With the increasing content of nano-CaCO3 particles, the porosity and average pore size of the modified membranes were increased, and the hydrophilicity was improved by decreased contact angle, which increased the membranes water flux and antifouling performance as well. Meanwhile, the modified membranes still maintained asymmetric structures. The attractive hydrophilicity caused partial aggregation of nano-CaCO3 in PVDF casting solution, which affect the dispersion of nano-CaCO3. And a best mechanical stability of modified membranes appeared at nano-CaCO3 concentration of 1.2 wt%.PVDF membranes with different contents of nano-ZnO particles were prepared by a phase inversion process. With the increasing content of nano-ZnO particles, the porosity of the modified membranes was increased; the hydrophilicity was improved by decreased contact angle, which led to the increase of the membranes water flux. The water flux and mechanical stability reached peak when nano-ZnO concentration was at 5 wt%. The results confirmed that the addition of 5wt% nano-ZnO could effectively dominate membrane pore structure and distribution, which improved membrane filtration performance and water flux. Nano-ZnO also improved membrane thermal stability effectively.
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