Preparation And Pervaporation Performance Of Crosslinked Poly(Vinyl-alcohol)/Hyperbranched Polyester Membranes

Conventional separation processes are characterized by high energy cost and high capital cost. Currently, membrane-based pervaporation (PV) is widely used in chemical engineering which is considered to be one of the most effective, suitable as well as energy-intensive method for theseparation of azeotropic and isomeric mixtures, temperature sensitive solutionsand liquid purification. What’s more, it does not need the adding of the third component(Azeotropic entrainer, such as benzene and toluene). So PV has significant advantages compared to conventional distillation.In this study, hyperbranched polyester (HBPE) was synthesized through a pseudo one-step reaction of molten state2,2-bis(hydroxymethyl)propionic acid and1,1,1-trimethylol propane using p-Toluene sulfonic acid as catalyst. Branching degree of HBPE polymer was46.56%determined by13C NMR. A new composite membrane of crosslinked poly(vinyl alcohol)/hyperbranched polyester (PVA/HBPE) was prepared using glutaraldehyde (GA) as crosslinking agent for the dehydration of ethylene glycol/water (EG/water) mixtures. The structure and the performance of PVA/HBPE membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and water contact angle. The mechanical properties of PVA/HBPE membranes were investigated by mechanical strength measurements. The testing results showed that PVA/HBPE membrane exhibited good thermal stability, high hydrophilicity and superior mechanical strength. Surface SEM images showed that when HBPE content was above40wt.%, the distribution of HBPE in the membrane matrix was poor and the phase separation between PVA and HBPE occurred.The pervaporation performs of PVA/HBPE membranes with the solution-diffusion theory were studied as well as the solubility parameter, diffusion coefficient and permeability coefficient were calculated. The results show that the prepared membranes are hydrophilic membrane. The increase of temperature of water or EG was benefit of the permeation, what’s more, the proper addition of HBPE is helpful for the increase of pervaporation flux of membrane. Influences of HBPE content, feed temperature and concentration on pervaporation performance were studied. PV experiments showed that, with the increasing of membrane HBPE content, feed water content and feed temperature, permeation flux increased significantly and separation factor decreased dramatically; the membrane containing10wt.%HBPE exhibited the best PV performance (permeation flux and separation factor were0.050kg/m2h and400respectively for the90wt.%EG solution at35℃). The results of PV are of roughly the same trend with the permeability coefficient (P).