Construction of dual-functional UGFM-PEEKWC-PEI composite membrane: Synergistic realization of high-flux ultrafiltration and efficient emulsion oil separation

Leveraging the excellent chemical resistance, thermal stability and structural tunability of the PEEKWC-PEI system, an UGFM-PEEKWC-PEI composite ultrafiltration membrane was fabricated by incorporating an ultrafine glass fiber membrane (UGFM) in conjunction with a controlled casting-solution dilution strategy. The influences of UGFM incorporation on the membrane microstructure, mechanical performance, surface wettability, and permeation behaviour and separation efficiency were systematically investigated. The results demonstrate that introducing UGFM effectively establishes a low-resistance mass-transfer pathway within the composite ultrafiltration membrane, markedly improving its mechanical properties and structural stability. Among the composite ultrafiltration membranes, the MGF-10 membrane exhibits the best overall performance, with the water contact angle reduced to 36.5° and the underwater oil contact angle reaching 138.7°, indicating pronounced hydrophilicity and underwater oleophobicity. At 3 bar, the membrane demonstrates a pure-water permeance of 1086.8 L·m −2 ·h −1 , with the pure-water flux reaching 5093.9 L·m −2 ·h −1 at 5 bar. The MGF-10 composite ultrafiltration membrane achieves a Congo red (CR) rejection of 98.1% at 3 bar, and maintains consistently high rejection toward dye solutions over a variable pressure range of 1–5 bar. Notably, even under high-salinity conditions (60 g/L Na 2 SO 4 ), the composite ultrafiltration membrane retains excellent dye separation capability, delivering a rejection of 91.7%, highlighting its promise for dye desalination via ultrafiltration. Results from static adsorption and dynamic filtration suggest that the composite ultrafiltration membrane predominantly removes dyes via a size-sieving mechanism, with adsorption providing an auxiliary contribution during the initial stage of filtration. Moreover, owing to interfacial regulation enabled by the formation of a surface hydration layer, the composite ultrafiltration membrane delivers excellent performance in surfactant-free oil-water separation, achieving separation efficiencies of up to 99.9% across multiple oil phases and exhibiting good operational stability over repeated cycles. Overall, the UGFM-reinforced architecture and casting-solution dilution control act synergistically to reduce mass-transfer resistance, enhance permeation flux, and sustain high rejection, offering a viable strategy for the structural design of high-performance composite ultrafiltration membranes.