Flux-enhanced polysulfone membranes blended with ABPBI as a novel additive

Abstract

Enhanced-flux polysulfone membranes were prepared with poly (2,5-benzimidazole) additive. Structural and morphological characterizations of prepared membranes were performed by using Scanning electron microscope and Infrared spectroscopy techniques. Hydrophilicity, porosity and pore structure of the composite membranes were investigated with wet-dry membrane weight and contact angle measurements. Flux, rejection and fouling resistance tests were performed by using cross-flow filtration studies. Scanning electron microscope images showed that a low ratio of poly (2,5-benzimidazole) additive increased the top and bottom skin layer thickness and membrane structure turned from finger-like to sponge-like but increasing the poly (2,5-benzimidazole) ratio changed the pore structure to finger-like again. Infrared spectra showed that good interactions were established between poly (2,5-benzimidazole) and polysulfone. Contact angles of the membranes decreased from 60 degrees to 38 degrees with the addition of poly (2,5-benzimidazole) which proved the excellent hydrophilicity of the membranes. Also increasing the hydrophilicity was supported by Infrared spectra. At 200 kPa, pure water fluxes of the membranes increased from 228 to 455 L/m(2).h. Bovine serum albumin rejection also increased with the addition of poly (2,5-benzimidazole), especially with low additive ratios. Flux recovery ratios of the membranes increased about 20% after the addition of poly (2,5-benzimidazole) and this showed that poly (2,5-benzimidazole) blended composite membranes have higher fouling resistance than pristine polysulfone membrane. Also, poly (2,5-benzimidazole) blended polysulfone membranes compared with poly [2,2-(m-phenylene)-5,5-bibenzimidazole] blended membrane which was our previous study. The comparison showed that that poly (2,5-benzimidazole) more effective and functional additive than poly [2,2-(m-phenylene)-5,5-bibenzimidazole] with its higher flux performance, fouling resistance and hydrophilicity characteristics. And also, poly (2,5-benzimidazole) additive more useful than poly [2,2-(m-phenylene)-5,5-bibenzimidazole] for using additive in membranes because of its so easy synthesis in one step, inexpensive monomer and low-cost advantages.