KOH-Activated Pinecone Biochar for Efficient Chloramphenicol Removal From Aqueous Solutions

The emerging pollutant chloramphenicol (CAP) is highly environmentally persistent and biotoxic, causing extreme environmental harm. This study investigates the removal of CAP from aqueous solutions using biochar derived from pinecones. The biochars were activated at 800°C using KOH with different mass ratios to the carbonized sample (2:1, 4:1, and 6:1). Among them, the biochar with a KOH ratio of 4:1 (PCK4-800) exhibits the highest pore volume (1.8 cm³ g⁻¹) and a specific surface area (3131.6 m² g⁻¹). Batch experiments reveal that the CAP adsorption capacity of the biochar is positively correlated with its specific surface area. At pH 7, PCK4-800 achieves a removal efficiency of up to 92% for a 100 mg L⁻¹ CAP solution using a dosage of just 0.1 g L⁻¹. This performance surpasses that of recently reported adsorbents. Kinetic and thermodynamic model fitting results indicate that chemical adsorption within a monomolecular layer dominates physical adsorption. The primary adsorption mechanisms involve pore filling and π-π interactions, while secondary mechanisms include electrostatic effects and hydrogen bonding. Thermodynamic parameters confirm that the adsorption process is endothermic and spontaneous. Moreover, the removal efficiency of PCK4-800 remains above 80% after five regeneration cycles. In summary, the high removal efficiency and excellent regeneration potential of PCK4-800 demonstrate its suitability as an effective adsorbent for antibiotic removal.