Preparation and characterization of antifouling graphene oxide/polyethersulfone ultrafiltration membrane: Application in MBR for dairy wastewater treatment

This study was performed to investigate effect of different concentrations of graphene oxide (GO) nanoplates on fouling mitigation of polyethersulfone (PES) membranes applied in membrane bioreactor (MBR) to treatment milk processing wastewater. The GO was prepared from graphite and characterized by FTIR, SEM and XRD. The mixed matrix membranes were prepared in three concentrations of 13, 15 and 17wt% of PES polymer. Static contact angle of the membranes were decreased significantly with addition of the GO nanosheets caused to increasing of pure water flux and MWCO. Cross sectional SEM images showed that the finger-like pores for all of the GO embedded membranes were slightly wider than that of the unfilled PES membrane. Ultrafiltration performance and fouling resistance of the membranes were tested by filtration of activated sludge. With addition of GO nanoplates, fouling resistance ratio (FRR) of the nanocomposite membranes was improved. AFM images and FRR results presented that a membrane with smoother surface has greater fouling resistance ability. Based on antifouling and water flux results, the PES/GO membrane with 15wt% of PES and GO content of 0.5wt%, was selected as an optimal membrane and tested in MBR system. The MBR showed an increased capacity for removal of organic matter, both in terms of COD and BOD₅ of milk processing wastewater. With increasing of MLSS concentration, flux of the membrane was increased due to a decrease in soluble microbial products and extracellular polymeric substance from the bacterial cells in the lower food to microorganism ratio (F/M).