A novel magnetic biochar prepared by K2FeO4-promoted oxidative pyrolysis of pomelo peel for adsorption of hexavalent chromium

Magnetic biochar was usually prepared using ferrous and ferric compounds as precursor of magnetic medium. Ferrate , which could be an internal oxidative modifier, was less explored for preparing magnetic biochar. Here, a magnetic biochar was prepared through K 2 FeO 4 -promoted pyrolysis of pomelo peel for adsorption of hexavalent chromium . Oxygen-containing groups and single phase ɤ-Fe 2 O 3 were simultaneously introduced into biochar matrix at 300 °C. The magnetic biochar exhibited 209.64 mg/g maximum adsorption capability at 45 °C, outperformed the best magnetic biochar with 142.86 mg/g maximum adsorption capability at 40 °C in the literature. Moreover, a good magnetism was obtained, facilitating separation of the magnetic biochar from aqueous solution by a magnet. The removal of hexavalent chromium was contributed to the hybrid adsorption of ɤ-Fe 2 O 3 and biochar matrix by reduction, electrostatic interaction and complexation. This method was attractive, required neither extra modifiers nor multiple operations for preparation of highly adsorptive magnetic biochar.