Graphene oxide functionalized polyethersulfone membrane to reduce organic fouling

Graphene-oxide can be used to modify a polymeric membrane surface to render the surface less susceptible to organic fouling. In this study, a three-step method is developed to covalently bind graphene oxide (GO) nanosheets onto a polyethersulfone (PES) support to create an ultrafiltration membrane that is resistant to organic fouling. First, amine functional groups are grafted onto a PES surface by UV-induced graft co-polymerization of allylamine monomer. Next, trimesoyl chloride (TMC, 0.2 wt% in hexane) and GO nanosheets (2, 4 and 6 wt% in anhydrous acetonitrile) are attached onto the polyallylamine modified membrane surface by spin coating, allowing covalent binding to take place between TMC and the amine functional group, and also between TMC and the hydroxyl or carboxylic functional groups of GO. Covalent bonding was confirmed by the emerging ester or anhydride peaks by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The GO membrane morphology was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The molecular weight cut offs (MWCO) of the GO (2, 4 and 6 wt%) modified membranes were determined to be 380, 140, and 75 kDa respectively. The membrane with 4 wt% GO (PES-GO-4) was chosen for further study because it exhibited higher pure water flux and rejection than the other GO formulations. The PES-GO-4 membrane exhibited 2.6 times greater flux recovery than an unmodified PES-UF membrane of comparable MWCO. This method is a simple, effective way to create a robust, high flux UF membrane that is resistant to organic fouling. Such a membrane could be applied in water or wastewater treatment applications, such as pretreatment for reverse osmosis.