Preparation?Structure Control And Properties Of Polyethersulfone Nanofiltration Membranes

A new nanofiltration membrane was prepared by phase inversion method with sulfonated polysulfone(SPSF)/poly(ether sulfone)(PES)/styrene maleic anhydride(SMA)in this paper.The sulfonated polysulfone(SPSF)and polyethersulfone(PES)as raw materials for preparing membrane,using polyvinylpyrrolidone(PVP)and styrene maleic anhydride copolymer(SMA)as additive,N,N-two dimethyl acetamide(DMAc)as solvent.The effect of material ratio on the membrane structure was studied at different SPSF and PES solid content,different amount of PVP addition,different amount of SMA added.Furthermore,the effects of pre evaporation time,pre evaporation temperature,coagulation bath temperature and casting temperature on the structure and properties of SPSF/PES/SMA blend nanofiltration membrane were discussed.In order to optimize the membrane,the membrane surface was modified by us,with formaldehyde as crosslinking agent,nanofiltration desalination were prepared for reaction of formaldehyde with maleic anhydride groups.We investigated the concentration of cross-linking agent,crosslinking temperature and crosslinking time on removal effect of salt structure and desalination rate,and we also explains the formation process of nanofiltration desalination.The results showed that with the increase of SPSF and PES solid content,the membrane water flux showed a decreasing trend on the whole,and the desalination rate of Na2SO4 increased.With the increase of the content of PVP,the viscosity of the casting film becomes larger,and the finger hole is inhibited.In addition,with the addition of SMA,the finger holes are eliminated,and the inner structure of the membrane becomes compact.When selecting SPSF and PES solid content is 25%,the additive content of PVP is 5%,the additive SMA content of 6% SPSF/PES/SMA blends prepared nanofiltration membrane performance is better.In the SPSF/PES/SMA system,With the increase of pre evaporation time,the water flux decreased and the desalination rate increased.With other conditions unchanged,the membrane water flux decreases and the desalination rate increases with the increase of the pre evaporation temperature.With the increase of coagulation bath temperature,membrane flux increases and the ratio of desalinization of Na2SO4 steady increases.Finally,the influence of the solution temperature on the performance of the film was investigated.With the increase of the temperature of the casting solution,the membrane water flux first increased and then decreased but desalination rate is the opposite.Considering the pre evaporation time is 90 s,the pre evaporation temperature is 70?,the coagulation bath temperature is about 25?,and the temperature of the casting film is at the temperature of 60?,which is the optimum process conditions for the preparation of the membrane,At the same time,the ratio of desalinization of Na2SO4 is 56.70%,the water flux is 39.96L/m~2·h.In order to optimize the membrane,the membrane surface was modified by us.With the increase of crosslinking agent concentration from 4% to 12%,the membrane rejection rate of Na2SO4 increased from 57.84% to 75.89%.Compared with the 56.70% of the basement membrane modified by formaldehyde,the modified membrane was superior to the basement membrane.Fixed other conditions unchanged,Increasing the cross-linking temperature is not conducive to the membrane with high water flux,and with the cross-linking time increased,the increase of the thickness of membrane,membrane flux decline.Overall consideration,when the crosslinking agent concentration is 10% and the cross-linking temperature is 90?,cross-linking time is 3h,the membrane desalination rate was 77.25%,and the water flux is corresponding to 13.75L/m~2 · h.