Preparation And Modification Of Polyvinylidene Fluoride Ultrafiltration Membrane

Polyvinylidene fluoride(PVDF)is a semi-crystalline polymer with excellent corrosion resistance,heat resistance,radiation resistance and chemical stability,and has good mechanical properties and good film-forming properties,therefore is widely used in the preparation of water treatment membrane.However,PVDF has low surface energy,high hydrophobicity,low water flux of pure PVDF membrane and easy adsorption of organic substances such as proteins on the membrane surface,resulting in membrane fouling,resulting in a decrease of membrane service life and increase of water treatment operation cost.Therefore,to improve the hydrophilic PVDF membrane called PVDF membrane modification of key research.In this paper,PVDF as the film-forming raw materials,prepared three types of additives on the PVDF blend modified PVDF membrane was obtained.The effects of the structure and content of additives on the morphology and properties of PVDF membranes were investigated.In this paper,hydroxylated MWCNTs-OH were synthesized and blended into PVDF based films as additives to improve the dispersibility of MWCNTs in solution and in polymer.The MWCNTs did not agglomerate,and the prepared MWCNTs-OH/PVDF composite membrane had high water flux and mechanical strength.The effect of MWCNTs-OH structure and content on membrane performance was investigated.When the diameter of MWCNTs-OH ranged from 20 to 30 nm,the tensile strength of MWCNTs-OH/PVDF composite membrane increased by 86%and the water flux reached as high as 243.3 L/m2h.In this paper,ZnO nanosheets have been successfully prepared and used for the first time in the blending modification of PVDF films.Compared with the spherical nano-ZnO modified film,the modified nano-ZnO modified PVDF composite film has a higher porosity,the water flux of the film is further improved,and the mechanical properties are good.In this paper,a new method of preparing MOF modified PVDF composite membrane is proposed.The copolymerization method was used to synthesize MOF in PVDF solution.After the phase separation,the MOF-5-PVDF supramolecular film was obtained.Compared with the MOF-5/PVDF blend membrane,the hydrophilicity of the membrane is further improved,with higher pure water flux and better anti-pollution performance.The pure water flux of MOF-5-PVDF supramolecular membrane is 160 L/m2h,which is seven times of that of pure PVDF membrane and 1.6 times that of MOF-5/PVDF membrane.The MOF-5-PVDF membrane's pure water flux recovery was still as high as 90%after three contamination experiments.