Oily wastewater treatment via phase-inverted polyethersulfone-maghemite (PES/γ-Fe₂O₃) composite membranes

In this study, phase-inverted polyethersulfone (PES)-maghemite (γ-Fe₂O₃) composite membranes were fabricated and tested for oil-water separation. The performance of five different composite membranes with various loadings of γ-Fe₂O₃ (0.25, 0.50, 0.75, and 1.00 wt.%) in terms of water flux, flux recovery, and oil rejection was investigated. The surface morphology, crystallinity, and functionalities of the membranes were characterized via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR). Furthermore, the porosity, pore size, water contact angle, and underwater oil contact angle of the composite membranes were examined. Results showed that the pristine PES membrane reported a pure water flux of 1242 ± 12 L/m²h (LMH) compared to 1323 ± 27 LMH for the 0.25 wt.% PES/γ-Fe₂O₃ membrane. Additionally, 56 and 23 % flux recovery ratio (FRR) were reported for the PES/γ-Fe₂O₃ and the pristine PES membrane, respectively. Also, the removal efficiency has increased from 39.2 % in the PES membrane to 81.7 % in the 1.00 wt.% PES/γ-Fe₂O₃ composite membrane. Two phenomena played a role in the removal trends, namely size exclusion and electrostatic repulsion forces. The developed membranes exhibited significant application potential for the removal of oil from wastewater.