Hardwood vessel-inspired chitosan-based sponge with superior compressibility, superfast adsorption and remarkable recyclability for microplastics removal in water

Microplastics (MPs) in water that are hazardous and recalcitrant pose formidable risks for human health, necessitating the development of efficient, sustainable removal methods. This study introduces a chitosan/bacterial cellulose sponge with superior compressibility and remarkable recyclability for polystyrene (PS) MPs rapid adsorption, inspired by the robustness and directional, rapid nutrient transport characteristics of hardwood vessels. The unique structure of sponge, featuring tunable oriented cellular channels and strong walls, is achieved via temperature-controlled directional freezing and double cross-linking. This structure enables the sponge to maintain high wet compressive reversibility, with a retention rate of 94.9% after 100 compression cycles. Moreover, the as-prepared sponge demonstrates a high MPs adsorption capacity of 0.26 mg·g−1. Owing to its excellent wet compressibility and adsorption performance, the sponge demonstrates remarkable cycling removal efficiency of 47.30% after 20 cycles. The experimental results together with theoretical fitting provide insight into how the hardwood-like structure and active sites of Chitosan enhance MPs adsorption. This work advances the development of efficient and sustainable MPs removal technologies using biomimetic and high-performance adsorbents and expands the insight into the MPs adsorption mechanism by chitosan-based sponge.