Fabrication and Characterization of Blend Polysulfone–Sulfonated Polyether Ether Ketone–Polyethylene Glycol Hollow Fiber Membranes for Separation of Oil-in-Water Emulsion via a Membrane Bioreactor Process

The membrane bioreactor (MBR) is a cutting-edge wastewater treatment technology that delivers exceptional effluent quality, compact design, and reliable operation by integrating biological treatment with membrane filtration. The performance of a MBR system heavily depends on the properties of the membrane used. In this study, blend polysulfone–sulfonated polyether ether ketone–polyethylene glycol (PSF–SPEEK–PEG) hollow fiber membranes were fabricated via a non-solvent-induced phase separation (NIPS) method. The effect of the SPEEK content on membrane characteristics and performance was investigated. Results showed that adding SPEEK enhanced the thermodynamic instability of the polymer solution, accelerating phase inversion and yielding a more porous structure with finger-like voids. The optimal membrane composition was achieved at a PSF/SPEEK ratio of 85:15, demonstrating: 75% overall porosity, 64.8° water contact angle (WCA), 13.48 nm mean pore size, and 680 kPa collapsing pressure. Due to its enhanced hydrophilicity and porosity, this membrane achieved a pure water flux (PWF) of 63.2 L m^–2 h^–1 and a hydraulic resistance of 5.8 m² h kPa L^–1. When tested in a MBR system, it maintained stable performance, achieving 99.8% oil rejection and a steady flux of 55.1 L m^–2 h^–1. In contrast, the SPEEK-free membrane suffered a 36% flux decline, attributed to higher oil fouling susceptibility. After 72 h of operation, the optimal membrane exhibited a flux recovery ratio (FRR) of 90.6%, far surpassing the 58.6% FRR of the SPEEK-free membrane. Additionally, it reduced the total fouling ratio from 42.5 to 12.8%, confirming its superior antifouling properties. These findings highlight the potential of SPEEK-modified membranes in MBR systems for high-efficiency oil-contaminated wastewater treatment.