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

Fenton modification, involving iron-promoted pyrolysis followed by H₂O₂ 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 H₂O₂ 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, CO and C-O groups by Fenton oxidation. More importantly, saturation magnetization could be enhanced by transforming nonmagnetic iron oxides into γ-Fe₂O₃ through H₂O₂ 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.