Phosphorus doped magnetic biochar activated PMS for effective degradation of pesticide in water: Targeted regulation of interfacial charge transfer by phosphorus doping

In this study, the incorporation of phosphorus (P) atoms into magnetic biochar was strategically achieved, and the preparation conditions of the composites were optimized by adjusting the pyrolysis temperature and iron doping. The resulting P-doped magnetic biochar (Fe2P@BC-700) exhibited remarkable catalytic activity towards peroxymonosulfate (PMS), rendering it highly effective for the degradation of common organic pesticides, such as 2-Methyl-4-chlorophenoxyacetic acid (MCPA), in aqueous environments. Among them, the apparent rate constant in the oxidation stage was 6.42 times as large as that of magnetic biochar (Fe2BC-700). This was attributed to the fact that the introduced P species tuned the surface electronic configuration of the pristine carbon layer with excellent electron storage and transport capabilities, and the Fe-O-P bonds in the composites acted as electron transport bridges to promote iron cycling in the magnetic nanoparticles during catalysis. The elimination of MCPA in the constructed adsorption enrichment-oxidative degradation system (Fe2P@BC-700/PMS) was achieved through a non-radical pathway dominated by singlet oxygen (1O2) and electron transfer process (ETP). It also ensured broad pH adaptability, environmental stability and repeatability. Density-functional theory calculated that ROS tended to attack the C-Cl branched chain in MCPA and the degradation products showed a tendency of toxicity reduction. This study provided new ideas for the design of market-oriented functional biochar catalysts.