Structure-performance nexus in biomass-derived biochars: How cellulose and lignin content govern porosity and...

The presence of antibiotic residues in aquatic ecosystems poses risks to both environmental and human health. Biochar adsorption is an effective removal technology, yet the relationship between activation methods and raw material characteristics remains unclear. This study used soybean pods and rice straw to produce biochar via grinding and impregnation, comparing their adsorption performance for tetracycline hydrochloride. Raw material differences were identified through elemental and component analyses, and activation parameters were optimized. Structural characteristics were assessed using N₂ adsorption-desorption, FT-IR, and XPS. The adsorption behavior of the optimal sample, RS-I-3-800-1, was evaluated through kinetics, isotherms, pH effects, ionic strength, real wastewater, and fixed-bed column experiments. Results show that grinding is more effective for carbon- and nitrogen-rich soybean pods, yielding a specific surface area (S_BET) of 1938 m² g^-1 and an adsorption capacity (Q_e) of 905.7 mg g^-1. In contrast, impregnation is better suited for cellulose-rich rice straw, achieving S_BET of 1832 m² g^-1 and Q_e of 1147 mg g^-1. The adsorption mechanism involves pore filling, hydrogen bonding, and π-π interactions, enabling stable performance across a wide pH range and in various water qualities. This study provides an experimental basis for selecting biochar activation methods based on the specific characteristics of soybean pods and rice straw.