Preparation And Application Of Polyvinylidene Fluoride Hollow Fiber Membrane Modified By Nano Hydroxyapatite

In order to improve the hydrophilicity and mechanical properties of polyvinylidene fluoride(PVDF)hollow fiber membrane,PVDF was used as the membrane matrix material,PVP as the porogen,and N,n as the pore forming agent,Using N-Dimethylacetamide(DMAC)as organic solvent,nano hydroxyapatite(HAP)as modified material,PVDF / HAP hollow fiber membrane was prepared by dry wet phase conversion method,and its structure and properties were studied.The effects of PVDF content,PVP content,dry process,core fluid flow rate and extrusion pressure on PVDF hollow fiber membrane were discussed.The following conclusions were drawn: with the increase of PVDF content,the viscosity of casting solution increased,the pore became dense and the pore wall thickened;With the increase of PVP content,the viscosity,spinnability and pore density of the casting solution increased,which affected the filtration and mechanical properties of the membrane;The higher the dry process,the slower the phase separation,the formation of pores or even no porous membrane,and the inner and outer cortex become thicker;With the increase of the core fluid flow rate,the membrane pore becomes larger and the wall thickness becomes thinner,and the inner part of the membrane is faster than the outer part;With the increase of extrusion pressure,PVDF macromolecules or segments are arranged more closely,which affects the structure and properties of the membrane.Compared with PVDF hollow fiber membrane,when the nano HAP content was 2.0%,the water flux of PVDF / HAP hollow fiber membrane increased by 34.7%;the hydrophilicity became better,the contact angle decreased from 65.5 ° to 46.0 ° with a decrease of 29.77%;the anti pollution ability was enhanced,and the FRR value reached 62.0%;the tensile strength also improved significantly.Therefore,nano hydroxyapatite can effectively modify PVDF film.The results show that the ultrasonic cleaning effect is remarkable,and the ultrasonic time is easy to control;the cleaning with Na OH solution and Na Cl O solution also has a certain effect,but the concentration is difficult to control,which is easy to damage the membrane;the cleaning with citric acid has no obvious effect.The removal rates of turbidity and chroma of lake water and Pearl River water by PVDF /HAP hollow fiber membrane are close to 100%,the removal rates of COD and UV254 of lake water are about 50%,and the removal rates of COD and UV254 of Pearl River water are more than 80%.With the increase of operation time,the water flux remained stable,and the removal effect of PVDF / HAP membrane on lake water and Pearl River water remained good.The FRR value of continuous filtration membrane was more than 95% after combined cleaning with ultrasonic and washing.