Polyethersulfone/Graphene Oxide Ultrafiltration Membranes from Solutions in Ionic Liquid
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Polyethersulfone/Graphene Oxide Ultrafiltration Membranes from Solutions in Ionic Liquid Dinesh. K. Mahalingam, DooLi. Kim and Suzana. P. Nunes King Abdullah University of Science and Technology (KAUST), Biological and Environmental Science and Engineering Division (BESE), 23955-6900 Thuwal, Saudi Arabia ABSTRACT Novel high flux polyethersulfone (PES) ultrafiltration membranes were fabricated by incorporating different amounts of graphene oxide (GO) sheets to PES as nanofillers. The membranes were prepared from solutions in 50/50 1-ethyl-3-methylimidazoliumdiethylphosphate/N,N-dimethyl formamide. It was observed that the water permeance increased from 550 to 800 L m-2h-1bar-1, with incorporation of 1 wt% GO, keeping a molecular weight cutoff (MWCO) of approximately 32-34 kg mol-1. Cross-sectional scanning electron microscopy images of GO/PES membranes showed the formation of ultrathin selective layer unlike pristine membranes. Contact angle measurements confirmed the increase of hydrophilicity, by increasing the GO concentration. The rejection of humic acid and bovine serum albumin was demonstrated. The mechanical properties were improved, compared with the pristine membranes. The performance was just above the trade-off relationship between permeance and separation factor for PES membranes reported in the literature.
INTRODUCTION The use of ionic liquids as solvent or co-solvent for the preparation of membranes has been explored by our group[1-4] and others[5], motivated by two aspects: (i) their low toxicity[2] and low vapor pressure, compared to solvents currently used in the industry for membrane manufacture, and (ii) their capacity of inducing different morphologies, guided by hydrogen bond and electrostatic interactions[6]. We prepared flat sheet cellulose membranes by dissolving in 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc)[1], hollow fiber membranes of polyacrylonitrile from solution in dimethyl sulfoxide/([EMIM]OAc[4] and of cellulose acetate in acetone/([EMIM]OAc[3], and hydroxyl-polytriazole in dimethyl carbonate/[EMIM]OAc[7]. PES is one of the most common membrane materials in the membrane industry for ultrafiltration and as support for reverse osmosis[8] with application in desalination, waste water treatment, biotechnology and pharmaceutical industries, oil-water separation, protein mixture separation, food industry and other filtration processes. While being an attractive material in membrane filtration, PES is known to be a hydrophobic polymer and is highly susceptible to fouling, without surface modification. We recently prepared PES membranes from solutions in 1-ethyl-3methylimidazolium diethylphosphate ([EMIM]DEP)[2] with molecular weight cut-off (MWCO) varying from 1.3 to 30 kg mol-1 and permeance values from 20 to 140 L m-2h-1bar-1, respectively. So far we only used ionic liquid for membranes fully constituted by organic polymers or block copolymers. However there is a large potential to explore casting solutions containing nanofillers such as graphene oxide (GO), which could be dispersed
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