Post-synthesis modification of polyethersulfone membrane by grafting hyperbranched polyethylene glycol for oily wastewater treatment

The main goal of this study is to modify the polyethersulfone membrane by the grafting hyperbranched polyethylene glycol (HB-PEG) via a two-step grafting method: (1) membrane surface activation with a photo-initiator under UV irradiation and (2) grafting HB-PEG onto the surface-activated membrane. The separation efficiency and fouling tendency of the modified membranes were evaluated for the treatment of a synthetic oily wastewater. A mechanism was proposed for the grafting reaction, and Lambert-Beer law was employed to determine the effect of benzophenone (BP) concentration as a photo-initiator on the grafting reaction. It was found that the rate of the grafting reaction has a maximum at the BP concentration of 0.33 mol/L. The FTIR and SEM analyses confirmed that the HB-PEG was successfully grafted on the surface of activated PES membranes. Moreover, the grafting HB-PEG onto the surface of the PES membranes alerted the surface hydrophilicity and led to the improvement of the anti-fouling property and oil-water permeation flux of all modified membranes without any remarkable changes in the oil rejection, as 48% and 52% enhancement in the pure water flux and oil-water flux were observed, respectively, compared to the neat PES membrane. Finally, the chemical stability of the modified membrane was investigated and the recovery of the fouled membrane after basic and acidic cleaning was 58% and 94%, respectively.