The Preparation Of PVC/SES Blend Membranes And The Effect Of The Degree Of Sulfonation On The Performance Of The Membranes

Membrane separation is a new and efficient separation technology,it has attracted muchattention for its advantages of high separation efficiency,no secondary pollution and low energyconsumption. Polyvinyl chloride (PVC) is the the second largest synthetic material with theadvantages of cheap, good chemical stability, microorganism erosion resistance,etc.It cause theextensive concern in the field of the development of new membrane materials.PVC also has theshortcomings like the strong hydrophobicity, the poor resistant to pollution and poor film-formingperformance,therefore the modification of hydrophilic and flexibility is urgently needed.Sulfonated poly (ether sulfone)(SPES) not only has the advantages of polyether sulfone (PES)like the good film-forming performance and good flexibility,but also has the stronghydrophilic,but the SPES is expensive.In this work,the PVC/SPES blend membranes wereprepared by the method of solution blending to combine the advantages of PVC and SPEStogether,so as to o develop a new type of cheap and excellent performance membranes.In this study,the SPES with different sulfonated degrees were prepared first by the method ofoleum sulfonation.Then the compatibility of the PVC/SPES blending systems and the influence ofsulfonation degree on compatibility of the system were characterized by the solubilityparameter,shear viscosity,fourier transform infrared attenuated total reflection(FTIR-ATR) and theglass transition temperature (Tg) respectively.On this basis,the PVC/SPES blend membranes wereprepared by the solvent-non-solvent diffusion-induced phase separation method.The optimumblending ratio were determined by the studying of the cross section and surface microstructurescanning electron microscope (SEM) figure and the performance include water flux, rejection rate,tensile strength,hydrophilic and antifouling properities) of the different blending ratiomembranes.On the basis of the determined of the optimum blending ratio,the influce of thedifferent sulfonation degree on the microstructure and the performance of the PVC/SPES blendmembranes were studied. The conclusions obtained by the research are as follows: 1.The results of the compatibility studies showed that the the PVC/SPES blending systems ispartially compatible.The blending systems with the blending ratio of9/1,8/2,7/3,2/8and1/9hadthe better compatibility.The Sulfonated degree has no effect on the compatibility.2.Within the blending ratios from10/0to0/10,the cross-section microstructure of thePVC/SPES blend membranes were changed from the typical asymmetric porous structure to thechaotic structure,and then changed from the chaotic structure to the typical asymmetric porousstructure.This is due to the different compatibility of the different blending ratios. Thecross-section microstructure of the PVC/SPES blend membranes with the blending ratios of10/0,9/1,8/2,7/3,2/8,1/9and0/10were the typical asymmetric porous structure and it were thechaotic structure with other blending ratios.The membrane water flux elevated first and thenreduced with the increase of SPES content in the blending system.When the blending ratio was4/6,the water flux was the maximum value.The hydrophilic of PVC/SPES blend membranes risedsharply with increase of SPES content in the blending system.When the blending ratio was7/3,namely the SPES content in the blending system reached30%, the hydrophilic tended to bestable.That is the hydrophilic of the blend membranes tends to be constant when increase theSPES content were increased continuely.This phenomenon is due to the intensity of the sulfonicacid groups and water molecules which caused the sulfonic acid groups gather on the membranesurface.Namely caused by the phenomenon of surface chromatography.In the perspective of theinfluce on the hydrophilic by the increase of the SPES content,the SPES content of30%of theblending system is enough, otherwise cost of the membrane will increase. The mechanicalproperties of the PVC/SPES blend membranes were superior to pure PVC membranes. Pollutionresistance experimental results show that the PVC/SPES blend membranes of blending ratio of8/2and7/3had good fouling resistances.The sewage flux of the two kind blend membranes after backflush were basically the same.The PVC/SPES blend membranes of blending ratio of8/2had thehigher BSA rejection rate and better mechanical properties that of blending ratio of7/3. Takingthe microstructure and the performance into account, the optimum blend ratio of PVC/SPES blendmembranes is8/2.3.The effect of the different sulfonated degrees of SPES on the cross-section microstructureand the surface microstructure of the PVC/SPES blend membranes showed that with the increaseof sulfonation degree,the pores of the cross-section structure became bigger and the spongystructure increased,the aperture of the pores of the surface structure became bigger and the number of it increase.With the improvement of sulfonation degree,the water flux of the PVC/SPES blendmembranes increased, and the BSA rejection rate decreased slightly.In addition, with the increaseof sulfonation degree, the mechanical properties,hydrophilicity,fouling resistances of themembranes had greatly improved.When the sulfonation degree increased from4.1%to16.9%,thewater flux of the blend membranes with blending ratio of8/2increased from56.74L/(m2·h) to115L/(m2·h) and the tensile strength,hydrophilic and antifouling performance of the blendmembranes with blending ratio of8/2is the best. Considering the performance of blendmembranes of different sulfonation degree,the increased of the sulfonation degree in theinvestigated range is helpful for the improving of the performanceof the blend membranes.