Sequential doping strategy for all-biomass derived N/P co-doped biochar: Unraveling the divergent capture mechanisms in antibiotic removal.

Biochar doping is widely applied for enhancing antibiotic removal from water, but most approaches still rely on synthetic chemicals and exhibit limited control over the incorporation of heteroatoms. Herein, a novel all biomass derived N/P-doped biochar (NP-CKBC) was fabricated from cork, chitin, and phytic acid via a sequential doping strategy for enhancing tetracycline (TC) and sulfamethoxazole (SMX) adsorption. The sequential doping utilized chitin-derived N to pre-stabilize the carbon skeleton, enabling subsequent phytic acid etching to form an interconnected porous network with ultra-thin walls and a high pore volume (1.16 cm3/g). Furthermore, this synergistic process simultaneously enhanced both graphitization and defect density, embedding abundant N/P active sites within the robust framework for efficient antibiotic capture. Driven by its hierarchical porous architecture and synergistically enriched N/P active sites, NP-CKBC achieved high adsorption capacities for TC (439.81 mg/g) and SMX (355.52 mg/g), rapid equilibrium kinetics (∼30 min), strong anti-interference ability, and superior continuous adsorption performance. Experimental characterizations and DFT calculations reveal that TC is captured via EDA and π-π interactions, whereas SMX is anchored through hydrogen bonding and electrostatic attraction. This work provides a sustainable strategy for preparing biochar from green biomass, offering a promising solution aimed at eliminating antibiotics within complicated aqueous systems.