Study On Hydrophilic Modification Of PVDF Membrane By Zirconium Based MOFs And MOFs-GO Composites

Polyvinylidene fluoride（PVDF）has excellent mechanical properties and chemical stability,widely used in the field of preparation of separation membrane materials.However,PVDF membrane has low surface energy,hydrophobic,and thus easy to be contaminated by organic matter such as proteins in the water clogging,which is easy to be polluted by organic pollution.Shorten the service life of the membrane and increase the operating cost of the membrane in practical production.Therefore,improving the hydrophilicity and anti-pollution performance of PVDF membrane has always been the focus and hot spot in the field of membrane separation.In this research,the aim is to improve the hydrophilicity of the PVDF membrane.the hydrophilic modification of the PVDF membrane by three different hydrophilic additives was studied under the same conditions as other conditions（synthesis method of additives,preparation method of blend membranes,solvent of casting solution,etc.）:adding hydrophilic Metal-Organic Frameworks（MOFs）materials and MOFs-GO（graphene oxide）composites.UiO-66/PVDF membrane,NH₂-UiO-66/PVDF membrane and NH₂-UiO-66-GO/PVDF membrane were prepared.The crystal structure,characteristic absorption peaks,surface and cross-section structure,surface roughness,surface chemical environment of the membrane were used to characterize by XRD,FT-TR,SEM,AFM,and XPS.At the same time,the porosity,water contact angle,water flux,rejection rate and anti-pollution performance of the membrane under different hydrophilic additives and different contents were evaluated.（1）MOFs materials UiO-66 crystals were synthesized by solvothermal method,UiO-66/PVDF blend membranes was prepared by NIPS,the structure and properties of the co-blended membranes were studied when the membranes contained different contents of UiO-66.The optimum content of UiO-66 in UiO-66/PVDF blend membrane was determined to be 1.67 wt%,the membrane water flux reached 120.6 L/（m²·h）,the rejection rate is 92.3%,the water contact angle is 65.46°and Sa is 17.2 nm.The experimental results show that the hydrophilicity of the membrane were improved.（2）Synthesis of derivatives of UiO-66:NH₂-UiO-66,and NH₂-UiO-66/PVDF blend membrane was prepared.The influence of different addition amount of NH₂-UiO-66 on the structure and properties of NH₂-UiO-66/PVDF blend membrane was studied.When the mass ratio of NH₂-UiO-66 to PVDF is 40%,the membrane had the highest water flux of 135.78L/（m²·h）,when the retention rate reached 94.99%,the rejection rate is 94.99%,the water contact angle is 60.42°and Sa is 15.1 nm.The experimental results show that the introduction of amino functional groups further improves the hydrophilicity of the membrane.（3）NH₂-UiO-66-GO composite material was synthesized by GO on NH₂-UiO-66,and NH₂-UiO-66-GO/PVDF blend membrane was prepared.The effects of different GO loading amounts on the membrane structure and properties were investigated.The optimal load of GO in NH₂-UiO-66/PVDF membrane was determined to be 6 wt%.the membrane water flux reached 148.79 L/（m²·h）,the rejection rate is 98.6%,the water contact angle is 54.78°and Sa is 13.5 nm.Among them,the load of GO improves the fouling resistance of the membrane.