Preparation Of New Porous Hollow Fiber Membranes

This paper presented the results of investigation concerning the formation and structure and separation properties of fiber membranes made of Polyvinylidine Fluoride(PVDF),Polyvinyl Chloride(PVC) and Polymethyl Methacrylate (PMMA).The miscibility of the polymer blends PVDF,PVC and PMMA was discussed.Furthermore,effect of dope composition,composition of coagulation bath and spinning conditions on structures and properties of PVDF/PVC/PMMA hollow fiber membranes were also investigated.The stability and fouling resistance of PVDF/PVC/ PMMA hollow fiber membranes were discussed.The porosity of the PVDF/PVC membranes was determined by SEM observations,and the separating properties of membranes were determined by measuring the water flux and retention coefficient of BSA solution,and the mechanical properties were determined by break strength and tensility.The polymer blends PVDF,PVC and PMMA are partial miscibility.While one component largely exists,a homogeneously casting solution can be obtained.The Influence of blend ratio,concentration of polymer,different additive and amount of additive on membrane properties were discussed.In order to investigate the effects of different factors on the properties of hollow-fiber membrane,the orthogonal table was designed with four factors and three levels.Through analysis of the conclusions of orthogonalizing experiment systematically,it confirmed that the membrane with PVDF/(PVC+PMMA) mass ratio 6:4,polymer concentration 17%,with 6%content of PVP as addition possessed the best-integrated property.Further more,the hollow fiber membrane prepared according to above optimum casting solution was proved to be the best.The temperature of the coagulation bath and spinning conditions all have a great effect on structures and properties of PVDF/PVC/PMMA hollow fiber membranes. Based on large amounts of studies of the influence of the technologcial conditions on the structures and properties of hollow fiber membrane,the results showed that it was the optimum conditions of casting solution that the temperature of coagulation bath was 25℃,inner solution concentration was 40%,bore liquid velocity was 13ml/min and dry length was 20cm.Under this conditions,the best performance of membrane was produced with the intention as 8.0Mpa,tensility as 32%,water flux as 623L/m~2·h, and retention ratio as 81%.PVDF/PVC/PMMA blends hollow fiber membranes with NaClO solvent post-treatment was studied and the results indicated that post-treatment with NaClO can increase water flux significantly but no distinct influence on retention.Acid and alkaline soak had little effect on mechanical property after membrane dipped in them. The results showed that PVDF/PVC/PMMA blend hollow fiber membranes owned good ability of resistance to acid and alkali in the broad pH range.The membranes were used in treatment of reactive BSA solution.Fouled membranes cleaned by water, membrane added PVP flux recovery higher than membrane free of PVP.It showed that PVP can improve hydrophilicity of membranes.It showed with property conditions we can prepared good membranes.And membranes modified by PVP had a more favorable antifouling performance and can be applied in wastewater treatment.