Preparation of modified ginseng straw biochar and its adsorption characteristics for flupyradifurone in water

This study utilized ginseng straw as a raw material to prepare ginseng straw biochar (GSBC) through high-temperature pyrolysis. The nitrate stannous chloride reduction method was employed to synthesize amino-modified GSBC (GSBC-NH₂) and the adsorption characteristics of GSBC-NH₂ for flupyradifurone in water were investigated. The results showed that after modification, the nitrogen content of the GSBC-NH₂ increased from 2.76% to 4.79%, and the specific surface area increased from 4.34 to 16.4 m²/g. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results confirmed the successful introduction of amino groups while maintaining a stable carbon skeleton structure. The adsorption capacity of GSBC-NH₂ for flupyradifurone in water was 6.63 mg/g, which is significantly higher than that of GSBC (2.78 mg/g). The adsorption kinetics of GSBC-NH₂ followed the pseudo-second-order kinetic model, and the Freundlich model better described the isothermal adsorption process, indicating that the adsorption was dominated by chemical adsorption and involved multilayer adsorption. Elevated temperature promoted adsorption, and the optimal adsorption occurred at pH 6-7. The primary mechanisms underlying flupyradifurone adsorption by the biochar included hydrogen bonding, π-π interactions, electrostatic attraction, hydrophobic interactions, and pore filling, among which hydrogen bonding played the dominant role. This study provides a theoretical basis for using amino-modified biochar to reduce residual pollution of polar pesticides in aquatic environments.