Converting herbal residues into adsorbents is a sustainable strategy for wastewater remediation. In this study, a hierarchical porous biochar (P-LBC) was engineered from liquorice residue via potassium oxalate-assisted pyrolysis. This activation reconstructed the carbon matrix, boosting the BET surface area to 1721.44 m²·g⁻¹ with an interconnected meso-microporous network. Compared with hydrothermal carbon (H-LBC) and unactivated pyrochar (LBC), P-LBC demonstrated superior adsorption capabilities toward chlortetracycline (CTC), attaining a maximum capacity of 278.05 mg·g −1 at 301 K. The adsorption kinetics and isotherms were well-described by the Pseudo-First-Order model and Langmuir equation, respectively, suggesting a rate-limited diffusion process leading to monolayer coverage. Thermodynamic analysis confirmed the spontaneous and thermodynamically favorable nature of the process. Analysis of the adsorption mechanism indicated that the outstanding performance of P-LBC originated from a synergistic interplay. While physical pore filling served as the primary mechanism, it was effectively supported by chemical mechanisms, namely hydrogen bonding, π−π interactions, and electrostatic forces. Furthermore, P-LBC showed robust adaptability across a wide pH range (4–11) and retained 70 % regeneration efficiency after five cycles. This work provides a cost-effective pathway for valorizing liquorice residue into a promising adsorbent for environmental purification. • Biochar prepared from licorice residue (TCM waste) realizes solid waste resource utilization. • Potassium oxalate-activated licorice residue biochar efficiently removes chlortetracycline. • Chlortetracycline hydrochloride removal involves multiple synergistic mechanisms.
Hua et al. (Thu,) studied this question.