Bio-Inspired Nanocellulose Aerogels for the Simultaneous Adsorption of Microplastics and Heavy Metals from Wastewater

Abstract

The contamination of global water resources by complex mixtures of pollutants, notably microplastics (MPs) and heavy metals, poses a severe threat to ecosystems and human health. Current water treatment technologies often struggle with the simultaneous removal of these disparate contaminants due to their different physicochemical properties. Inspired by the hierarchical, multifunctional structures found in nature, this study presents the design, fabrication, and evaluation of a novel, multifunctional aerogel composed of TEMPO-oxidized cellulose nanofibers (TOCNF) and chitosan, engineered for the synergistic adsorption of both MPs and heavy metal ions. The three-dimensional (3D) porous network of the TOCNF aerogel provides an excellent scaffold for high-flow wastewater treatment, while the chitosan incorporation introduces protonated amine groups for efficient metal chelation. A key bio-inspired innovation is the functionalization of the aerogel's internal surface with tannic acid, a plant-derived polyphenol, which creates a high-affinity "capture layer" through hydrophobic and hydrogen-bonding interactions for MPs. The aerogel was characterized using SEM, BET, FTIR, and XPS, confirming its hierarchical micro/nanoporous structure, high specific surface area (≥ 152 m²/g), and successful functionalization. In batch adsorption experiments, the aerogel demonstrated exceptional removal efficiencies, achieving >99% for lead (Pb(II)) and cadmium (Cd(II)) ions at concentrations of 50 mg/L, and >95% for polyethylene (PE) and polypropylene (PP) microplastics (size range 50-500 µm) at concentrations of 100 mg/L. In a continuous flow column study simulating real wastewater conditions, the aerogel maintained high removal efficiency (>90% for both pollutant classes) for over 50 bed volumes. The adsorption mechanisms were thoroughly investigated, revealing ion exchange and complexation for metals and hydrophobic interaction for MPs. This work provides a sustainable, scalable, and highly effective strategy for tackling complex water pollution, leveraging bio-inspired design and renewable materials to advance next-generation water remediation technologies.