The Preparation Of PVB/SPES Blend Membranes And The Effects Of The Degree Of Sulfonation On The Performance Of Membranes

Membrane separation technologies have the advantages of low energy consumption,suitable for the separation of heat-sensitive material, bigger separation factor,easy recycling and no secondary pollution. Therefore, it has broad applying prospect.However, current commercial membranes are expensive, and membrane foulingsharply increases the frequency of backwashing, so the lifetime of membranes isimpaired. Poly (vinyl butyral)(PVB) as a low cost material, can endure the lowtemperature, light, change in humidity, microorganism, alkali and diluent acid. PVBhas hydrophilicity but hydrophilic is not very strong. In addition, PVB is brittle and notgood enough in the membrane forming property and permeability, which restricts thefurther application of PVB membranes. So research and development of highly hydrop-hilic and highly permeable PVB membranes is urgently needed. Sulfonated poly (ethersulfone)(SPES) is synthesized through sulfonation reaction by introducing sulfonicgroups onto amino-substituted polyethersulfone (PES). SPES not only retains the PESexcellent performance, but also enhances hydrophilicity and permeability of PESmembranes. In this work, the low-cost PVB/SPES blend membranes were prepared toimprove the hydrophilicity, water flux, and anti-fouling performance of PVBmembranes.The research contents and results of this paper mainly includes the following aspects:1. In this work, the compatibility of the PVB/SPES blending systems with differentblend ratios and different degree of sulfonation (DS, DS were0.09,0.15and0.27,respectively) were characterized by the solubility parameter，shear viscosity, FourierTransform Infrared Attenuated Total Reflection (FTIR-ATR) and differential scanningcalorimeter (DSC), respectively. Results stated that all PVB/SPES blending systemswere partially miscible and the higher value of DS, the better compatibility. 2. SPES was blended with PVB (with blend ratios of PVB/SPES that varied from10:0to0:10) through a solvent–non-solvent diffusion-induced phase separation method tofabricate PVB/SPES blend membranes. The surface morphologies and cross-section ofthe membranes with different blend ratios were observed by scanning electronmicroscope (SEM). The experimental results showed that the blend membranes, whichhad a better compatibility showed typical asymmetric structures, finger-like poroussub-layers and dense skin layers. Nevertheless, the structures of cross section of blendmembranes were irregular, when the blend membranes had a poor compatibility. Thewater flux and rejection of blend membranes had a well-regulated change with blendratios of PVB/SPES that varied from10:0to0:10. Both the water flux and rejection ofthe PVB/SPES blend membranes (with blend ratios varying from9:1to7:3) are higherthan that of pure PVB membranes. Both the tensile strength and tensile elongation ofthe PVB/SPES blend membranes (with blend ratios varying from10:0to0:10) had thesame change tendency. Both the tensile strength and tensile elongation of PVB/SPESblend membranes (with blend ratios varying from9:1to7:3) were higher than that ofpure PVB membranes. The increase of mechanical properties was mainly caused by themorphologies of the membranes and partially miscible. When the blend ratio ofPVB/SPES was7:3, the blending system was useless for the enhancement ofmechanical properties of pure PVB membranes. Furthermore, fouling resistances ofblend membranes evaluated by bovine serum albumin (BSA) solution filtrationrevealed the PVB/SPES blend membranes with blend ratio of7:3exhibited the superiorantifouling properties. Taking the water flux and rejection and antifouling properitiesinto account, the optimum blend ratio of PVB/SPES blend membranes was7:3.3. In this work, the PVB/SPES blend membranes with different DS (DS were0.09,0.15and0.27, respectively) were prepared. The effects of the degree of sulfonation on themorphologies of the membranes with the blend ratios of8:2was studied, the results ofSEM indicated that the surface pores of blend membranes became bigger and the porenumber increased with increasing DS. Meanwhile, the effects of the degree ofsulfonation on the water flux and rejection of the membranes, the results showed thatthe water flux and rejection of blend membrane revealed the same phenomenon withdifferent DS, and the water flux increased while the rejection decreased with increasing DS. The results of hydrophilicity experiments explicated the higher value of DS, thestronger hydrophilicity of blend membranes, which attributable to the presence ofsulfonic groups. In summary, with increasing DS, the blend membranes exhibited abetter properities.