A highly efficient strategy for enhancing the adsorptive and magnetic capabilities of biochar using Fenton oxidation.

• Fenton oxidation was first applied for presice modification of biochar. • Incorporating iron into biochar matrix through pyrolysis was of great importance. • A considerable number of oxygen containing groups were introduced. • Great increase of adsorption capability was obtained for Cr (VI) and MB. • Fenton oxidation leaded to increase of saturation magnetization. Fenton modification, involving iron-promoted pyrolysis followed by H 2 O 2 oxidation, was first employed to improve the adsorptive and magnetic capabilities of biochar. Modified biochars were prepared from rubber tree bark and coconut shell through iron-promoted pyrolysis and subsequent H 2 O 2 oxidation, and their adsorption behaviors toward Cr (VI) and MB were evaluated in aqueous solution. The modified biochars pyrolyzed at 300 and 400 ˚C displayed much higher adsorption capabilities than corresponding pristine biochars for Cr (VI) and MB, respectively, ascribing to introduction of COOH, C O and C–O groups by Fenton oxidation. More importantly, saturation magnetization could be enhanced by transforming nonmagnetic iron oxides into γ-Fe 2 O 3 through H 2 O 2 oxidation. The removal of Cr (VI) and MB could be primarily contributed to the adsorption of biochar matrix by reduction/hydrogen bonding/cation exchange/electrostatic interaction and hydrogen bonding/cation exchange/electrostatic interaction, respectively. This would provide a novel and efficient strategy for making highly adsorptive magnetic biochar. [ABSTRACT FROM AUTHOR]