A three-step process to produce biochar with good magnetism, high specific surface area, and high levels of nitrogen doping for the efficient removal of sulfamethoxazole

Efficient sorbents that have high sorption capacity and suitable separability are promising and are urgently needed to remove diverse contaminants from water environments. In this study, nitrogen-doped magnetic porous biochars (NMPBs) were synthesized from marine algae by a three-step process consisting of prepyrolysis, copyrolysis and coprecipitation. For NMPBs, the surface area was up to 1531 m2/g, the magnetization strength was up to 31 emu/g, and the surface nitrogen content was up to 3 %. The NMPBs showed the expected sorption capability for sulfamethoxazole, with the removal quantity reaching 502 mg g−1 based on the sorption isotherm model. NMPBs also showed excellent separability and reusability, and the removal rate remained at 87 % after seven cycles. Partitioning and adsorption, including pore filling, hydrogen bonding, π-π stacking, partitioning and electrostatic interactions, were the sorption processes in removing sulfamethoxazole. In this work, marine algae were converted into an engineered biochar that is promising for environmental remediation.