Hierarchically porous and anisotropic biochar from fast-growing balsa and paulownia woods for effective microplastic removal

Microplastics (MPs) pollution has emerged as a critical global environmental challenge. Biochar has emerged as a promising sustainable adsorbent for MPs removal, owing to its abundant raw material sources, high production yield, and recyclability. However, current limitations persist, including poor adsorption performance and ambiguous molecular interaction mechanisms. This study addresses these gaps through controlled pyrolysis of fast-growing balsa and paulownia woods to synthesize hierarchically porous biochar. The optimized biochar exhibited an exceptional adsorption capacity for polystyrene (PS) of 533.33 mg g^-1, driven by multiple intermolecular interactions. Notably, it retained 88.4% of its initial capacity after 30 regeneration cycles. Moreover, the biochar exhibited robust MPs removal across diverse water matrices, low MPs concentrations (1 mg L^-1), and real-plastic particles (plastic bags and tea bags). This work not only advances the rational design of sustainable MPs remediation materials, but also elucidates molecular-level adsorption mechanisms, providing both practical solutions for MPs mitigation and operational guidelines for water treatment facilities.