Fish Gill-Inspired Bidirectional Porous Polysaccharide Aerogels for Micro/Nanoplastics Removal

Micro/nanoplastics (MNPs) pose a threat to freshwater ecosystems and human health due to their intrinsic toxicity, leaching of harmful degradation byproducts, and transport of pollutants through food chains. However, the efficient removal of MNPs using conventional methods such as filtration, flocculation, and biodegradation remains a significant challenge. Inspired by the structure of fish gills, we developed a sustainable bidirectionally porous polysaccharide-based aerogel composed of chitosan (CS), cellulose nanofibers (CNFs), and polydopamine (PDA) for the effective removal of MNPs. The aerogel demonstrated outstanding adsorption capacities exceeding 300 mg/g for various MNP types, including carboxylated polystyrene (PS-COOH), PS, poly(methyl methacrylate) (PMMA), polyethylene (PE), and polypropylene (PP). In particular, the bidirectionally oriented porous structure achieved an adsorption capacity of more than 9 times greater than that of randomly oriented aerogels. Molecular dynamics (MD) simulations revealed that this high adsorption performance is attributed to strong multimodal interactions between the aerogel and MNPs, including electrostatic interactions, van der Waals (vdW) forces, hydrogen bonding, and π-π interactions. A benchtop continuous-flow adsorption column system was constructed, enabling an MNP removal efficiency of over 96% for 1 L of MNP-contaminated water within four purification cycles and a total of 20 min. Additionally, the aerogels exhibited excellent antibacterial activity against <i>E. coli</i> in acidic environments. Overall, with its large adsorption capacity, high water flux, and remarkable antibacterial properties, these bioinspired aerogels offer a scalable and sustainable solution for efficient MNP remediation from wastewater streams. This work uncovers how directional pore alignment, tailored surface chemistry, and multimodal interactions synergistically enhance the adsorption of diverse MNP species.