Preparation And Properties Of PVDF/SiO 2 Composite Membranes

With the development of society and economy,the pollution of heavy metal wastewater has seriously affected the life and health of human beings.Traditional methods of removing heavy metal ions,such as chemical precipitation,membrane filtration and adsorption,have been widely applied to all aspects of production and life.Adsorption method has been considered as an excellent method because of its simple operation and low cost.However,due to unstable adsorption capacity and low regeneration efficiency of adsorbents,its application is limited.Mesoporous silica has been widely concerned by researchers because of its large surface area,high porosity and easy surface modification.However,mesoporous silica usually exists in the form of particles,which leads to the accumulation of reunion in the adsorption process,and it is easy to drain and cause two pollution.Therefore,finding proper method to fix the mesoporous silica will be the focus of the study.Polyvinylidene fluoride(PVDF)has the advantages of resistance to oxidation,strong mechanical properties,easy to film formation and so on.It is a kind of film material with excellent performance.However,due to the poor hydrophilicity of pure PVDF membrane and the fact that it has no active sites,its adsorption capacity for heavy metal ions is small and selective adsorption is poor,which affects its application in water treatment.In recent years,researchers have added functional groups such as amino,sulfhydryl,hydroxyl to the PVDF membrane to achieve the adsorption of heavy metal ions by chelating.In this study,functional groups were first introduced into mesoporous silica spheres by hydrothermal synthesis to obtain the functionalized mesoporous silica.Then,two kinds of PVDF/SiO2 composite membranes were prepared by fixing silicon spheres on the PVDF membranes by blending and copolymerization respectively.The composite membranes were characterized by FTIR,SEM,BET and TG respectively to analyze the structure and physical properties of the composite membranes.The study results of adsorption show that two kinds of composite membranes have good adsorption capacity on Pb2+ and Cu2+.The adsorption capacity of PVDF/IIMS(Pb)hybrid membrane to Pb2+ in aqueous solution increased with the increase of pH value at lower pH,and reached the maximum when pH was 6.Howere,the pH value reached 7,the adsorption capacity decreased.With the increase of the volume,time and initial concentration of the solution,the adsorption capacity increases first and then tends to balance.The adsorption capacity of PVDF/Cu2+imprinted mesoporous silica hybrid membrane to Cu2+ in aqueous solution increased with the increase of pH value at lower pH,and reached the maximum when pH was 5.5.When pH value reached 6,the adsorption capacity decreased.With the increase of the volume,time and initial concentration of the solution,the adsorption capacity increases first and then tends to balance.After five repeated tests,it is proved that the hybrid membrane has good reutilization performance.