Amphiphilic Ti<sub>3</sub>C<sub>2</sub>/exfoliated bentonite@polyurethane sponge grafting both hydrophobic groups and polar oxygen-containing groups for efficient removal of multi-polar microplastics.

Abstract

Owing to the intrinsic polarity differences among various microplastics (MPs), conventional adsorbents commonly enable to remove monotypic MPs from wastewater. Waste polyurethane (PU) sponges with abundant sources exhibit a certain potential for adsorbing MPs of varying polarities due to physical interception, but they are constrained by insufficient adsorption sites and inferior cyclic reusability. This study reused waste PU sponge by incorporating polar oxygen-containing functional groups and tailoring hydrophobicity, successfully constructing amphiphilic Ti₃C₂/exfoliated bentonite@polyurethane sponge (Ti₃C₂/BTex@Sponge). Ti₃C₂/BTex@Sponge demonstrated excellent adsorption ( >99 % within 30 min) for six representative MPs (Polar MPs: PVC100 [100 mesh] and ABS100 [100 mesh]; Non-polar MPs: PS100 [100 mesh], PE100 [100 mesh], PP100 [100 mesh] and PP2000 [2000 mesh]) at 0.1 g·L^-1. Moreover, adsorption efficiency of MPs was sustained at over 98 % even after 10 adsorption-desorption cycles. Meanwhile, Ti₃C₂/BTex@Sponge maintained stress retention at 80 % strain and exhibited adaptability over a broad pH range (3.0-11.0), which demonstrated its exceptional mechanical and chemical stability. The adsorption mechanisms of Ti₃C₂/BTex@Sponge toward MPs was identified as a synergistic process: (1) Hierarchical porous structure (0-50 nm) captured MPs via capillary force, while tailored surface roughness Ra = 156 μm) enhanced physical anchoring. (2) Polar oxygen-containing groups formed hydrogen bond-dipole interactions with polar MPs. (3) Hydrophobic surface generated van der Waals forces with non-polar MPs. The strategy proposed in this study to tailor amphiphilic adsorption sites not only realizes high-value upcycling of waste PU sponges but also opens a novel approach for efficient removal of MPs with different polarities.