Ferric nitrate/dopamine/melamine-derived nitrogen doped carbon material as the activator of peroxymonosulfate to degrade sulfamethoxazole

•Preparation of nitrogen-doped carbon materials from inexpensive raw materials.•Explored the influence of different raw materials on catalyst performance.•Graphitization and nitrogen doping have vital effect on degrading sulfamethoxazole.•Graphite nitrogen and Fe-Nx are the main active sites.•Free radicals bound to the catalyst surface are considered to be mainly active oxygen.