Performance Study On PVDF Composite Ultrafiltration Membrane Modified Using Nanocomposite GO/ZrO₂

Polyvinylidene fluoride（PVDF）membranes have excellent oxidation and mechanical properties and are a widely used polymeric organic membrane material,but PVDF membranes are strongly hydrophobic,which can reduce the membrane’s anti-fouling properties,thus increasing operating costs and limiting the application of PVDF membranes in water treatment.It is therefore necessary to improve the hydrophilicity of PVDF membranes,thereby increasing the resistance of PVDF membranes to contamination.In this study,PVDF composite ultrafiltration membranes were prepared using different nanomaterials（GO,ZrO₂nanoparticles and GO/ZrO₂nanocomposites）and the effects of nanomaterials on the morphology and properties of PVDF composite ultrafiltration membranes were investigated,speciafically as follows.（1）Graphene Oxide（GO）was prepared by a modified Hummers method and GO/ZrO₂nanocomposites were prepared by hydrothermal synthesis.The physical and chemical properties of the nanomaterials were analysed by XRD,TEM,FTIR and SEM,and the results showed that both GO and GO/ZrO₂nanocomposites were successfully prepared.（2）ZrO₂/PVDF,GO/PVDF and GO/ZrO₂/PVDF composite ultrafiltration membranes were prepared by the submerged precipitation phase transformation method.The microscopic morphology,crystal structure,porosity,molecular structure,average pore size and hydrophilicity of the PVDF composite ultrafiltration membranes were characterized by XRD,FTIR,XPS,SEM,AFM and contact angle meter.The final results show that the nanomaterials have been successfully compounded in PVDF membranes,and that the PVDF composite ultrafiltration membranes modified with nanomaterials have increased porosity and improved hydrophilicity.（3）When the additions of GO,ZrO₂nanoparticles and GO/ZrO₂nanocomposites in PVDF composite ultrafiltration membrane were all 0.75 wt.%,the pure water fluxes of the membranes reached 348.56 L/（m²·h）,294.58 L/（m²·h）and 376.28 L/（m²·h）,respectively,comparing with the pure PVDF membrane,the pure water fluxes increased by 173.6%,131.2%and 195.4%,the retention rates of sodium alginate（SA）increased by 18%,13%and 24%,bovine serum protein（BSA）increased by 21%,14%and 31%,humic acid（HA）increased by 18%,10%and 29%,and the contact angle decreased from 81.4oto 66o,69.8oand 61.4o.The surface roughness of pure PVDF membrane is 23.1nm,while the surface roughness of GO/PVDF,ZrO₂/PVDF and GO/ZrO₂/PVDF composite ultrafiltration membrane is32.7nm,26.8nm and 36.2nm respectively.The flux recovery rate of GO/PVDF,ZrO₂/PVDF and GO/ZrO₂/PVDF composite ultrafiltration membrane reaches 78.9%,73.5%and 85.8%respectively,which greatly improved the anti-pollution performance of the membranes.The tensile strength increased from 2.93 MPa to5.11 MPa,4.21 MPa and 6.46 MPa for pure PVDF membranes.（4）Comparing the performance of GO/PVDF,ZrO₂/PVDF and GO/ZrO₂/PVDF composite ultrafiltration membranes,it was found that the GO/ZrO₂nanocomposite increased the porosity of the membrane to the greatest extent,and it exposed the most hydrophilic oxygen-containing functional groups,so the GO/ZrO₂/PVDF composite ultrafiltration membrane had the best hydrophilicity.The excellent hydrophilicity of GO/ZrO₂/PVDF composite ultrafiltration membranes makes it easier to form a dense hydrated layer on the membrane surface,which can improve the retention of contaminants of different molecular weight such as BSA,HA and SA,resulting in the best anti-pollution performance.GO/ZrO₂/PVDF composite ultrafiltration membranes also have the best mechanical strength and chemical stability.Thus,GO/ZrO₂nanocomposites can significantly improve the hydrophilic performance and fouling resistance of membranes and are a promising hydrophilic modification material.