High-performance caffeic acid-based superhydrophilic membranes for efficient removal of microplastics-oil co-contaminants.

Microplastic-oil co-contaminants have raised high environmental concerns due to their persistence and synergistic toxicity. However, conventional separation membranes, typically designed for single-pollutant removal, are ineffective against such complex systems. Moreover, the strong interfacial interactions between microplastics and oil promote aggregate formation, leading to severe membrane fouling and compromised separation performance. Herein, we present a robust, antifouling, and superhydrophilic membrane fabricated via sodium periodate-assisted co-deposition of caffeic acid and ε-polylysine for simultaneously removing both oil droplets and microplastic particles from contaminated water. The resulting caffeic acid/ε-polylysine composite superhydrophilic membrane achieves an impressive separation efficacy for various oil-in-water emulsions and polystyrene microplastics of different sizes. Notably, it exhibits superior separation performance for challenging microplastic-oil co-contaminants, with rejection of 99.89% for oil and 96.99% for 100-nm polystyrene microplastics over 300-min continuous filtration. It also sustains a high flux recovery, reflecting robust antifouling properties and thus highlighting a great potential for practical application in complex wastewater treatment. Additionally, the membrane shows a remarkable antibacterial activity even after 30 days of immersion. This study demonstrates a scalable and sustainable strategy for fabricating high-performance polyphenol-based antifouling membranes, offering an effective solution to manage these emerging co-contaminants.