Nitrogen-doping positively whilst sulfur-doping negatively affect the catalytic activity of biochar for the degradation of organic contaminant

Developing low-cost and efficient metal-free carbon-based catalysts is of great importance but remains a challenge. In this work, rice straw derived biochar was prepared and doped with heteroatoms (N and S) for the catalytic degradation of metolachlor (MET) through activating peroxymonosulfate (PMS). Adsorption process played a critical role for the subsequent degradation process. Surface ketone C (-C = O) was the catalytic active sites for the PMS decomposition. Interestingly, N-doping positively whilst S-doping negatively influenced the MET degradation process. Through experimental investigation and theoretical calculations, N-doping was demonstrated to be beneficial for the interaction between biochar and PMS, thus accelerating the catalytic degradation process. The reactive oxidative species involved in the degradation process were explored by EPR analysis. The degradation pathways were elucidated based on the liquid chromatography time-of-flight mass (LC-TOF-MS) analysis of the degradation products. This study highlights the applications of biochar for the environmental catalysis.