Tiered biomimetic polydimethylsiloxane coated polyurethane sponge for sustainable seawater nanoplastic removal

Microplastics (MPs) and nanoplastics (NPs) are ubiquitous in the environment, posing great ecological risks. Compared with MPs, the unique colloidal and penetrating characteristics of NPs pose formidable challenges to traditional MPs removal technologies, resulting in great difficulty in NPs removal. Herein, through tiered biomimetic design via simulating sponge spicule structures, lotus surface engineering and alveoli mechanical compressibility, we developed a polydimethylsiloxane (PDMS) coated polyurethane (PU) superhydrophobic sponge (PDMS@PU) by dip-coating and ultrasonication for the removal of NPs. PDMS@PU demonstrated a maximum sorption capacity of 406.9 mg/g, rapid sorption within 30 s and 91.7 % sorption retention after 30 regeneration cycles for polystyrene nanoplastics with particle size of 240 nm (PS-NPs-240), significantly exceeding those reported in current literature. The interconnected channels of sponge facilitate the transport of NPs to sorption sites through amplifying capillary capture, the lotus leaf inspired superhydrophobic PDMS coating with micro-roughness effectively traps them, and the alveoli-like compressibility enables excellent reusability. PDMS@PU demonstrates significant environmental robustness under high-salinity, eco-corona interference and wide spectrum of NPs. Scaled-up experiments achieve 96.2 % PS-NPs-240 capturing by PDMS@PU. This work innovatively provides a sustainable water remediation method for combating NPs pollution through biomimetic wisdom.