Enhanced catalytic activity of rice husk biochar for antibiotics degradation: Synergistic effects of copolymerization and mineral removal

Effective utilization of rice husk (RH) biomass is essential to mitigate the environmental issues associated with it. Though RH biochar has been widely studied as a metal free carbon catalyst for persulfate activation , its performance is often limited by low active site density. In this study, we propose a two-step strategy to enhance RH biochar’s active site density through copolymerization , and mineral etching process. This design strategy enables the creation of new metal-free active centers and enhances the exposure of existing active sites on the RH surface, thereby effectively overcoming the limitations of metal leaching in metal/carbon composite systems . The prepared RH biochar/copolymer composite catalyst displayed excellent tetracycline (TC) removal efficiency with peroxydisulfate. Composition optimization results showed RH biochar with 33 wt% of copolymer derived carbon has high TC degradation efficiency. Furthermore, the removal of mineral impurities significantly enhanced the catalytic efficiency, enabling a 50 % reduction in the catalyst concentration while maintaining the same level of degradation performance. An increased specific surface area of the catalyst boosts the catalytic efficiency. Electron spin resonance spectroscopy (ESR), scavenging experiments, and electrochemical studies confirmed that tetracycline degradation occurs mainly through electron transfer pathway. The composite also displayed a satisfactory TC degradation performance with anions and in real groundwater conditions. This study introduces a novel strategy for creating metal-free active centers on RH biochar, offering a promising solution for real-world water treatment applications. • Copolymerization and silica etching boosted rice husk biochar’s catalytic activity. • The biochar showed excellent tetracycline degradation efficiency with persulfate. • The method reduces catalyst use from 100 to 50 mg L –1 without affecting efficiency. • Tetracycline oxidation occurs via electron transfer, minimizing radical generation.