Study On The Effect Of SiO₂ Nanoparticles On PVDF Ultrafiltration Membranes And The Mechanism

PVDF is a material of ultrafiltration and microfiltration membranes with preferable foreground in application, but its hydrophobicity and weak intensity restrict its abroad application in water treatment. So improving the hydrophilicity and the intensity of PVDF membranes is urgent. The study on nano-inorgnic/organic membrane has been received much attention recently. Hydrophilic nanoparticles may improve the hydrophilicity and mechanical property of membranes.This paper first researched the possibility of PVDF-SiO₂ hybrid membranes formed by wet phase inversion. The results show that a uniformity steady transparent clear solution can be made by dispersing the SiO₂ nano-particles into the mixed solvent with ultrasonic, then PVDF and other additives were added into SiO₂-solvent solutions and a uniformity steady casting solution was formed by whisking. This paper studied the effect of SiO₂ nanoparticles on the viscosity of casting solutions and gel processes by which membranes were formed, and then researched the rule of the effects of SiO₂ naoparticles on ultrafiltration performances and mechanical properties of membranes and the mechanism.The results of this study indicated that the presence of SiO₂ make the viscosity of casting solutions increase. The contact angle of membranes falls from 71°to 63°because of the abundant hydroxyl group on the surface of membranes. The hydrophilicity of membrane increases.SiO₂ naoparticles improve the porosity, pure water flux and Youngs module of the PVDF membrane without any additives and decrease the intensity with constant BSA retention. When additives were added,SiO₂ could make the hybrid membrane with more additives dense, intensity increased,the pure water flux decreased and Youngs module increased,but it is turned over for the membranes with little additives, the pure water flux increased and Youngs module decreased. In any case, SiO₂ made little effect on the BSA retention of hybrid membranes.FTIR spectra showed no chemical bond exist in hybrid membrane, X-ray diffraction found PVDF crystal,SiO₂ nanoparticles made crystal ratio of PVDF membranes without any additives increase and crystal ratio of PVDF membranes with additives decrease. Results of DSC measurements show that the crystal melting point and melt enthalpy have hardly any change and the thermal properties of the PVDF...