An efficient and general oxidative magnetization for preparation of versatile magnetic porous biochar at low temperature

Oxidative magnetization is an emerging method for manufacturing versatile magnetic biochar at comparatively low pyrolysis temperature, benefiting to reducing functional groups decomposition with low energy consume. A magnetic porous biochar was manufactured by a novel oxidative magnetization [KMnO4/Fe2(SO4)3 accelerated pyrolysis of kelp at 300 °C] for removing three kinds of contaminants from aqueous solution. Spherical nanoscale Fe3O4 was massively doped with introduction of oxygen functional groups simultaneously. Remarkable increase of surface area and pore volume was also observed. Benefiting from these factors, remarkably increased adsorption capability and saturation magnetization were achieved. The magnetic biochar possessed 145.71, 72.58, and 322.48 mg/g maximum adsorption amounts for Cr6+, methylene blue, and tetracycline with 17.11 emu/g saturation magnetization, respectively, in which nanoscale iron oxides and oxygen functional groups made significant contributions. Furthermore, KMnO4/Fe2(SO4)3 accelerated pyrolysis showed superior generality for fabricating high-performance magnetic biochars using diverse bio-wastes at low temperature. [Display omitted] •Spherical nanoscale Fe3O4 was massively doped.•Abundant oxygen functional groups were generated.•Significant enhancement of pore volume and surface area was observed.•High adsorption capabilities were obtained for different contaminants.•Good saturation magnetization was achieved at low temperature.