Upcycling Industrial Polyphenylsulfone Waste into a High-Performance, Non-fluorinated Photothermal Membrane for Sustainable Desalination

Photothermal membrane distillation (PMD) offers a sustainable pathway for freshwater production, yet its progress depends on developing high-performance membranes made from environmentally benign materials. To address the growing concern over the environmental persistence of fluorinated polymers, this study utilizes non-fluorinated, postindustrial polyphenylsulfone (w-PPSU) waste as a sustainable polymer source for fabricating photothermal membranes. Electrospun w-PPSU nanofibers were surface-modified with magnetite/black titania (Fe₃O₄/b-TiO₂) nanocomposites synthesized at varying b-TiO₂ concentrations and subsequently sealed with a thin hydrophobic polydimethylsiloxane (PDMS) coating. The best-performing membrane (M-F/bT-50) demonstrated rapid solar-driven heating, elevating its surface temperature to 91.1 °C within 120 s under 1 kWm^-2 irradiation. In desalination tests at a minimal temperature difference (Δ<i>T</i> = 15 °C), this membrane achieved a water flux of 3.27 Lm^-2h^-1, a salt rejection of 99.74%, and a photothermal conversion efficiency of 69.87%. Furthermore, the membrane maintained performance over multiple acidic cleaning cycles, demonstrating high flux recovery and regenerability. This work not only introduces an effective material system for efficient desalination but also establishes a viable pathway for valorizing industrial polymer waste into advanced, environmentally responsible technologies, contributing directly to the principles of a circular economy.