| In this paper,non-solvent induced phase inversion(NIPS)method was used to prepare fluorocarbon special surfactant FS-30 blended PVDF membrane and levofloxacin(LVFX)blended PVDF membrane.The special properties of fluorocarbon special surfactants were used to achieve a simultaneous increase in membrane rejection and flux.The levofloxacin was used as an additive to achieve the dual properties of hydrophilicity and antibacterial of the membrane.Firstly,the effects of different addition amounts of FS-30 on the structure and properties of PVDF membranes were investigated under PVDF/Li Cl/FS-30/DMAc system.The addition of FS-30 significantly improved membrane performance and achieved a simultaneous increase in the pure water flux and BSA rejection of the membrane,which was of great value for membrane application.With the addition of FS-30,the pure water flux increased from 114.68?LMH of the original membrane M0 to 393.76?LMH of the blend membrane M7.At the same time,the BSA rejection rate of the membrane was also increased continuously when the FS-30 content was less than 5 ? wt% and reached 99.48% at M5.The change in membrane properties can be attributed to the phase inversion process as well as the morphological structural features of the membrane.The addition of FS-30 increased the porosity and improved the hydrophilicity of the membrane by28.06%.However,the average pore diameter of the membrane was reduced from 0.339??m to 0.241??m and a special “stage pore” structure was produced due to the unique properties of FS-30.Fourier transform infrared(FTIR)spectroscopy and X-ray diffraction(XRD)imaging showed that FS-30 was lost during the coagulation bath and did not remain on the membrane,but affected the crystal composition of the ?-phase and ?-phase in PVDF membrane as well as promoted the phase inversion process to instantaneous phase separation.Meanwhile,the effect of FS-30 on the morphology of the membrane was characterized by scanning electronmicroscopy(SEM),and the morphological changes of the membrane was analyzed from the aspects of thermodynamics and kinetics of the casting solution in combination with the phase inversion process of the membrane.It was found that the influence of FS-30 on the kinetics of the casting solution did not balance the effect on the thermodynamic instability,and the thermodynamic effect still dominated,making the FS-30 blend membrane have a more obvious asymmetric structure.Moreover,the effect of the blend membrane on the rejection of algae in surface water and bacteria in sewage was also characterized with the help of chlorophyll fluorescence technique and bacterial inoculation culture experiments respectively,and the result confirmed that the FS-30/PVDF membranes had excellent properties.Secondly,the effects of different amounts of LVFX on the performance of PVDF membranes under PVDF/PVP/LVFX/DMAc system were investigated.The effects of levofloxacin as additive on membrane structure and properties were investigated.Fourier transform infrared spectroscopy(FTIR)?scanning electron microscope(SEM)and contact angle were used to characterize the existence of levofloxacin on PVDF membrane and its influence on membrane morphology and hydrophilicity.The antifouling performance and antimicrobial activity of LVFX/PVDF blend membrane were evaluated respectively by static adsorption of BSA,decay of circulating flux,inhibition zone and inhibition rate.The results showed that levofloxacin was present on the membrane stably.With the increase of the levofloxacin ratio,the contact angle of the blend membrane decreased from 77.7 ° to62.1°,the hydrophilicity of the membrane was enhanced.The BSA static adsorption capacity decreased while the flux recovery rate increased,the irreversible pollution index decreased to 11.8% when the addition ratio of LVFX was 0.6%,which possessed the best antifouling ability.The inhibition zone was formed when the addition ratio of LVFX was 0.3%.When the adding ratio was 0.6%,the antibacterial rate could reach 92.3%,showing excellent antibacterial properties.In addition,the blend membranes was regenerated after run for a period of time,still maintained a goodantibacterial effect. |
PDF Full Text Request