Hydrophilic Modification Of Hyperbranched Polyester And Itseffect On PVA Membrane Of Pervaporation Performance

Pervaporation (PV) is acknowledged as a well-established membrane separation technology with high efficiency and low energy consumption for its applications in separation and purification of liquid mixtures. Extraordinarily it has been mostly applied in dehydration of organic solvents. For dehydration of organic solvents, the high hydrophilicity of membrane materials becomes essential. Poly (vinyl alcohol) (PVA) is an excellent hydrophilic membrane material. PVA membranes have achieved more and more concern in making it more suitable for dehydration and improving its functions. Hyperbranched polymers have a highly branched structure, not easy to crystallize, almost no chain entanglement, containing a variety of functional groups. Besides the industrial synthesis of hyperbranched polymers is relatively simple and low-cost, thus growing number of people begin exploring and developing the application of hyperbranched polyester (HBPE).In this work, The hyperbranched polyester was synthesized by melt polycondensation approach in a stepwise manner, wherein pentaerythritol (PEL) as core molecules with the aid of p-TSA as catalysis reacted with bis-MPA which was recognized as the AB2 monomer. Water-soluble hyperbranched polymer (WHBP) was synthesized through the modification of hyperbranched polyester (HBPE) by the reaction between hydroxyl end-groups and maleic anhydride, and its structure was characterized by NMR and FTIR. The novel crosslinked WHBP/PVA membranes were prepared using glutaraldehyde as crosslinker, the structure and properties were characterized by FTIR, XRD, SEM, TG, mechanical capacity, and water contact angle. The results show that the WHBP/PVA membranes exhibit good thermal stability, strong mechanical properties and high hydrophilicity.Then the sorption and diffusion behaviors of WHBP/PVA membranes in n-butanol and water were investigated. The experimental results demonstrated that WHBP/PVA membranes has more selective toward water, and with the increase of WHBP content, the sorption selectivity enhanced. The resulting membranes were tested for pervaporation separation 10 wt.% water/n-butanol solution at 60 ℃. It is observed that with increasing the amount of WHBP in the membranes the permeation flux increased and the separation factor decreased, the PSI firstly increased and the n decreased. The M-3 (10wt.%) showed the best PV performance with the highest PSI of 2.31×105. For intrinsic properties of membrane, with the increasing WHBP content, the permeability increased and on the contrary permselectivity decreased. The M-3 also exhibit a relatively high permeability 4.00×10-3 gm-1 h-1 kPa-1 and acceptable selectivity 785.In conclusion, the M-3 (10wt.%) membrane performed well with optimal pervaporation performance for the separation of 10 wt.%water/n-butanol mix.ture.So we selected M-3 to conduct the following study. The effect of feed concentration and temperature on pervaporation performance was investigated. The results showed that with the increase of water content PSI decreased, but PSI value still maintained high. The temperature has great impact on pervaporation performance and higher temperature will promote the pervaporation separation.