Superhydrophilic super-aligned carbon nanotube membrane for efficient oil/water emulsion separation

The effective treatment of oily wastewater, particularly stable oil/water emulsions, remains a significant challenge due to the lack of advanced separation materials that concurrently offer high permeability, superior selectivity, and robust antifouling stability. To address these challenges, this study develops a super-aligned carbon nanotube (SACNT) membrane with tailored superhydrophilicity and underwater superoleophobicity via a rational two-step surface engineering strategy, involving polydopamine priming and subsequent grafting of aminated SiO 2 nanoparticles. The morphology, chemical composition, and wetting behavior of the membranes were systematically characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and contact angle measurements, while its separation performance was evaluated in terms of molecular weight cut-off (MWCO), water permeability, oil rejection rate, and long-term antifouling stability. The sequential deposition of polydopamine and aminated SiO 2 nanoparticles enabled the construction of a highly ordered, cross-stacked CNT framework with uniform nanopores, achieving a water contact angle of ∼0° within 1 s and an underwater oil contact angle of ∼155°. The resulting membrane demonstrated exceptional separation efficiency (>99.2% oil rejection) and outstanding antifouling stability, maintaining >70% flux recovery over ten filtration cycles, which was attributed to its well-defined nanopores (MWCO ∼530 kDa), high water permeability (7.22 × 10 −6 m s −1 kPa −1 ), and stable hydration layer. This work provides a generalizable platform for designing high-performance, durable separation membranes through bottom-up nanoscale engineering, opening a viable path toward the development of advanced CNT-based materials for sustainable water purification.