Rapid synthesis of Co-loaded biochar by flash Joule heating for efficient degradation of metronidazole via peroxymonosulfate activation

The utilization of metal catalysts to activate peroxymonosulfate (PMS) for degrading organic contaminants is an effective strategy for addressing organic wastewater challenges. Flash Joule heating (FJH) is a novel thermochemical technology for the rapid synthesis of functionalized materials. FJH technology can rapidly raise temperatures above 2000 °C in a short period of time, which partially mitigates the energy inefficiency and long cycle times of conventional thermochemical technologies. Co-loaded flash biochar (FJH-Co/BC) was prepared by the impregnation-FJH method. FJH-Co/BC showed good pore structure and large surface area, and loaded cobalt species. FJH-Co/BC effectively activated PMS for the degradation of metronidazole (MNZ). Under the conditions of catalyst 40 mg/L, PMS 1 mM, and temperature 25 °C, 100 % removal of MNZ was obtained within 60 min. The reaction system showed good performance for MNZ degradation over a wide pH range (3−11). The catalytic system degraded MNZ by both radical pathways (SO₄^•– and ·OH) and non-radical pathways (¹O₂ and electron transfer), and the non-radical pathway played a major role. The loaded Co species in FJH-Co/BC were the main contributor to the generation of reactive oxygen species from PMS activation, and flash biochar played the role of Co support and facilitator of electron transfer. The degradation pathway of MNZ in the catalytic system was revealed, and the toxicity assessment confirmed the low ecotoxicity of the degradation intermediates. This work provides a novel strategy for the efficient synthesis of metal-loaded catalysts for the catalytic degradation of organic contaminants.