Catalyzed in-situ amination of support layer for thermally stable forward osmosis membranes in industrial dyeing wastewater concentration

Forward osmosis (FO) offers a promising wastewater treatment option with energy efficiency and lower membrane fouling than pressure-driven processes. However, its practical application remains constrained by operational temperature limitations, particularly in high-temperature industrial dyeing wastewater treatment. Inspired by the muscle that effectively controls the movement of seashells, this study employs a homogeneous catalyst to rapidly modify polyacrylonitrile support layers using bridging molecules that mimic such structures. During interfacial polymerization, one end of the molecular bridge is covalently anchored to the support layer and the other to the active layer, thereby enhancing interfacial adhesion and yielding a thermally stable FO membrane. After anchoring, the glass transition temperature ( T g ) of the polyamide active layer on the modified support increases to 90.08 °C. Utilizing 1 mol/L NaCl as the draw solution and deionized water (DI) as the feed solution, the J w of the FO membrane increased from 33.6 ± 3.9 (L∙m −2 ∙h −1 ) at 25 °C to 110.3 ± 9.98 (L∙m −2 ∙h −1 ) at 90 °C under AL-DS mode. The reverse salt flux ratio ( J s / J w ) remained nearly constant at 0.26 (g∙L −1 ). In addition, the FO membranes also exhibit superior anti-fouling properties. In a 48 h concentration experiment using actual industrial dyeing wastewater, the membranes sustained a stable J w of 20.0 ± 0.92 (L∙m −2 ∙h −1 ). Not only 83 % of the industrial dyeing wastewater was recovered, but also the contaminants in the wastewater were forced to aggregate by external concentration polarization. This study proves FO membrane feasibility in harsh industries and presents a scalable route to high-performance membranes for high-temperature wastewater.