Sustainable tannic acid-based polyurethane foam for enhanced microplastic removal and antibacterial water purification

Microplastic (MP) pollution is a critical environmental concern due to its persistence, bioaccumulation, and toxicity. Conventional polyurethane filters, while widely used in water treatment for their porosity and flexibility, suffer from large, non-uniform pores (>60 μm) and lack intrinsic antibacterial properties, limiting their efficiency. To overcome these issues, we developed an eco-friendly, multifunctional polyurethane foam (PUF) incorporating tannic acid (TA), a natural polyphenol. TA provides strong antibacterial and antioxidant activity and functions as a bio-based crosslinker within the polyurethane matrix, enhancing foam stability. Increasing the TA content creates a more robust network structure, thereby decreasing the average pore size by 85.4% (from 65.6 μm to 9.6 μm) and enhancing the removal efficiency for microplastics of various sizes. Furthermore, filtration tests using real wastewater demonstrated a 91.9% reduction in bacterial counts (from 1,215 to 98 CFU mL⁻1), confirming the antimicrobial efficacy of the material. TA-incorporated PUF achieve simultaneous removal of MP and microorganisms. The reactive incorporation of TA creates uniform pores while preserving the mechanical integrity of conventional polyurethane, making it a promising material for advanced wastewater treatment.