Characterization of the plasma-modified polysulfone membrane and its use in a membrane bioreactor

This study investigates the effects of plasma surface modification parameters—specifically gas type, plasma power, and treatment duration—on the performance of commercial polysulfone (PS) membranes in a membrane bioreactor (MBR) treating synthetic fruit juice wastewater. Two gases (H₂O vapor and N₂) were tested at different power levels (40-100 W) and exposure durations (1-30 min). The membrane characteristics were evaluated using contact angle, FTIR, SEM, and AFM analyses. Operational performance was assessed under varying organic loading rates (OLRs: 0.5, 1.0, and 2.0 kg COD m⁻³ d⁻¹), including flux and resistance profiles. Results showed that increasing plasma power and exposure time significantly improved membrane hydrophilicity and roughness. The optimal condition—H₂O plasma at 100 W for 30 min—reduced the contact angle by 53% and increased surface roughness by 371%. These surface enhancements directly translated into improved filtration performance: the equilibrium flux increased by up to 44%, and total membrane resistance (Rt) decreased by up to 51%. Among the resistance components, cake resistance (Rc) remained the dominant factor under all conditions. To the best of our knowledge, this is the first study to systematically optimize plasma treatment parameters for PS membranes in an MBR treating high-strength industrial effluent. This work addresses a critical research gap by linking specific plasma parameters to long-term hydrophilicity, fouling resistance, and filtration stability, thereby providing a scalable, environmentally friendly approach for industrial wastewater treatment.