Adsorption of TC by K2HPO4/KHCO3 Co-modified corn straw pith biochar: Synergistic enhancement mechanism of hydrogen bonding and pore filling

Tetracycline(TC) contamination necessitates effective remediation. Utilizing agricultural waste like corn straw pith offers a sustainable route to develop high-efficiency adsorbents for removing antibiotics from aquatic systems. A novel dual-modification strategy was developed using agricultural waste corn straw pith as the precursor. This approach combined K 2 HPO 4 -assisted hydrothermal pretreatment with KHCO 3 solid-state activation to synthesize a high-performance biochar adsorbent designated as KPBC-800. The resulting material was characterized to analyze its pore structure and surface chemistry. Additionally, adsorption experiments were conducted to evaluate its capacity for tetracycline removal, kinetic behavior, isotherm models, pH adaptability, and resistance to ionic interference. The synthesized KPBC-800 exhibited an ultra-high specific surface area of 1991.40 m 2 /g and a layered micro-mesoporous network, alongside directionally enriched oxygen-containing functional groups. It demonstrated a maximal tetracycline adsorption capacity of 722.02 mg/g, with the process following the pseudo-second-order kinetic and Langmuir isotherm models. The adsorbent showed broad pH adaptability and excellent resistance to ionic interference. Mechanistic studies revealed that superior performance resulted from the synergy of hydrogen bonding, π-π electron donor-acceptor interactions, and effective pore filling. This work demonstrates a feasible dual‑activation strategy for upgrading agricultural waste into a high‑performance biochar adsorbent, providing insights that may inform the design of efficient antibiotic removal materials.