Modification Of PVDF Ultrafiltration Membrane And Its Application

Membrane separation is an economic,efficient and environmental-friendly technology which can be used for separation,concentration and purification.Nowadays,polyvinylidene fluoride(PVDF)is one of the most extensively used materials in membrane manufacturing processes due to its excellent comprehensive properties,such as superior thermal stability,outstanding corrosion resistance,stable structure,superb mechanical strength,excellent chemical resistance and good antioxidant activity,etc.Nonetheless,the hydrophobic nature of PVDF membrane makes it susceptible to contamination by proteins and some of other impurities in water treatment system.leads to susceptible contamination in water treatment,which causes a sharp drop in the water flux during the memberane filtration process,reduce the service life,eventually result in the increasing of membrane replacement cost.So that the hydrophobic becomes a major obstacle for PVDF membrane to widespread in membrane technology.To take better use of PVDF membrane in water treatment technology,hydrophilic modification methods of blending and in situ co-precipitation reaction were combined.A novel poly(vinylidene fluoride)(PVDF)/graphene oxide(GO)membrane with an amount of silver carbonate(Ag2CO3)deposition was prepared by both the phase-inversion method and the in situ co-precipitation reaction,respectively.The casting solution of Ag2C03@PVDF/GO membrane(AgC-PGM)is composed of PVDF as the polymer matrix,GO and Ag2CO3 powders as additives,PVP30 as the pore-forming agent,and dimethylacetamide(DMAc)as the solvent.The basic performance and separation performance were investigated by BSA,HA and toluene respectively,Then resistance analysis,MFI comparison,static adsorption property and desorption property were discussed to sudy its anti-pollution performance.Finally,Fourier transform infrared(FT-IR)spectra and field emission scanning electron microscope(FESEM)image were obtained for investigating the changes of membranes caused by modification.The results indicated that the AgC-PGM exhibited good hydrophilicity and filtering quality,and the pure water flux increased from 132.8 L/m2·h of PVDF membrane to 237.4 L/m2 ·h,meanwhile the rejection for the BSA solution stabilized around 75%as the GO loading amount to 0.4wt.%,AgNO3(5.OmM)/Na2CO3(2.5mM)precipitating 3 times.Compared to PVDF membrane,the contact angle of AgC-PGM decreased 10° and the hydrophilicity is remarkably improved;The flux decay rate decreased by 45%and the flux recovery rate was up to about 80%;furthermore,the results of membrane resistance analysis showed that membrane resistance of composite membranes decreased clearly especially irreversible membrane resistance and the anti-pollution improved significantly.In addition,compared to PVDF membrane,the 3-D EEM of surface water shows a good removal effect of the protein pollutant after blending GO and precipitating Ag2CO3,the removal efficiency of both CODMn and UV254 separately achieved about 95%and 83%when the AgC-PGM was used to filter the lake water continuously,which has reached to the national primary standard.