Plant-based fiber filter layers enabling simultaneous polystyrene nanoplastics removal and in situ hydrophobic paper fabrication.

Nanoplastics have raised significant concerns due to their intrinsic toxicity and synergistic interactions with co-occurring pollutants, posing substantial risks to aquatic ecosystems and human health. Herein, we developed a plant-fiber-based co-filtration system incorporating alum as a retention aid, enabling efficient removal of polystyrene nanoparticles (PS) from aqueous solutions via a simple process. This process achieved exceptional removal performance, with a PS removal efficiency of 98.32%. Materials characterization combined with Density Functional Theory (DFT) simulations revealed that the efficient interaction between plant fibers and PS nanoplastics arises from the synergistic contribution of van der Waals forces and electrostatic interactions. Additionally, following thermal treatment, the filter-layer-derived paper demonstrated excellent hydrophobicity with a water contact angle of 120° and a water permeability resistance of 1759.8 s, which was comparable to that of paper produced via conventional sizing process, and it maintains structural stability under wet-dry cycles and ultraviolet irradiation. Collectively, this work demonstrates that plant-fiber-based co-filtration system achieves highly efficient removal of PS nanoplastics from aqueous environments, while simultaneously imparts durable hydrophobicity to inherently hydrophilic paper substrates, thereby advancing a potentially scalable, green manufacturing strategy aligned with clean production principles.