Study On Modification Of Polyethersulfone Ultrfiltration Membranes

In the paper,the PES/SiO₂ hybrid membranes were prepared by wet phase inversion method.It was investigated that the effects of micron silica dioxide(μ-SiO₂) and nanometer silica dioxide(n-SiO₂) on the performance of PES membrane.Meanwhile,as additives of PEG or MPC blending into the PES hybrid composite,its effects on the properties of PES membrane were evaluated.The method of NMR spin-lattice relaxation time T₁ value of PES was used to determine effect of SiO₂.Blending SiO₂ into the PES solution,the T₁ value decreased.The thermodynamic phase diagrams of different PES composite systems were independently achieved.Comparison with PES system,PES/SiO₂ system and the PES/SiO₂ with PEG or MPC hybrid system,their phase curves moved to the polymer/solvent axis to some degree in the thermodynamic phase diagram.It was indicated that the phase separation process of casting solution could be faster,in other word,the results showed that the phase separation speed increased in a certain degree and the membrane forming speed fasted.Meanwhile the pure water flux and the retention rate of PES/SiO₂ hybrid membrane were improved in a different degree.The PES/PVC blend membranes were prepared by wet phase inversion.The effects of PVC on PES/PVC blend membranes were evaluated.The results showed that the slope of kinetic curve was increased.As the increasing of the concentration of PVC in PES/PVC system,the pure water flux and the retention rate of PES/PVC blend membranes were improved synchronistically.Blending small quantity ofμ-SiO₂ into PES/PVC system,the PES/PVC hybrid blend membranes were prepared.The result showed that the slope of kinetic curve was increased. With increasing the content ofμ-SiO₂ in PES/PVC system,the pure water flux of PES hybrid membrane tended to increase except for a little bit decrease in initial,meanwhile the retention rate decreased slowly.Regarding the MPC blended PES/PVC/SiO₂ hybrid membrane,the slope of kinetic curve still increased.With increasing the content of MPC in a certain range,the pure water flux and retention of PES hybrid membranes were increased gradually.The UV radiation grafting modification experiments on the PES membrane were achieved through one way and two steps,and the grafting ratio were evaluated.The results showed that the PES membrane with higher grafting ratio via method of two steps.In this paper the PES membranes were used to treat the papermaking black liquor.The results showed that the removal rate of chemical oxygen demand(COD) and chromaticity could be up to 55.37%and 40.13%respectively.The analysis of fractal theory indicated that it could be used to quantification morphology and microporous structure of PES hybrid membrane.