Polyethersulfone membranes: from ultrafiltration to nanofiltration via the incorporation of APTS functionalized-graphene oxide

In this study, graphene oxide (GO) functionalized with 3-aminopropyltriethoxysilane (APTS) functionalized graphene oxide (GO) nano-fillers was incorporated into polyethersulfone (PES) membranes prepared by non-solvent induced phase inversion (NIPS). This resulted in increased rejections of protein bovine serum albumin (BSA), divalent salts (MgSO4) and low-molecular weight dyes (sunset yellow and acridine orange). The structural properties of the prepared mixed matrix membranes (MMMs) as well as pure PES control membranes were investigated through scanning electron microscopy (SEM), atomic force microscopy (AFM), specific surface area, zeta potential and contact angle. It was found that the introduction of APTS-GO fillers in the polymer matrix made the membranes’ application range move from ultrafiltration (UF) for pure PES membranes to nanofiltration (NF) for MMMs with a molecular weight cut off (MWCO) of ∼1000 Da. Furthermore, membranes prepared by using only 0.1 wt% APTS-GO in combination with 1 wt% of pore-forming agent polyvinylpyrrolidone (PVP 40K) in the casting solution exhibited high water permeance values of 9.9 LMHbar (L m-2 h-1 bar-1) at low operating pressures of 4 bar and rejections of dyes and BSA > 95%. In addition, improved anti-fouling properties and tensile strength values were obtained when incorporating the functionalized GO.